WSL2-Linux-Kernel/fs/xfs/linux-2.6/xfs_aops.c

1585 строки
39 KiB
C
Исходник Обычный вид История

/*
* Copyright (c) 2000-2005 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_trans.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_error.h"
#include "xfs_rw.h"
#include "xfs_iomap.h"
#include "xfs_vnodeops.h"
#include <linux/mpage.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>
STATIC void
xfs_count_page_state(
struct page *page,
int *delalloc,
int *unmapped,
int *unwritten)
{
struct buffer_head *bh, *head;
*delalloc = *unmapped = *unwritten = 0;
bh = head = page_buffers(page);
do {
if (buffer_uptodate(bh) && !buffer_mapped(bh))
(*unmapped) = 1;
else if (buffer_unwritten(bh))
(*unwritten) = 1;
else if (buffer_delay(bh))
(*delalloc) = 1;
} while ((bh = bh->b_this_page) != head);
}
#if defined(XFS_RW_TRACE)
void
xfs_page_trace(
int tag,
struct inode *inode,
struct page *page,
unsigned long pgoff)
{
xfs_inode_t *ip;
loff_t isize = i_size_read(inode);
loff_t offset = page_offset(page);
int delalloc = -1, unmapped = -1, unwritten = -1;
if (page_has_buffers(page))
xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);
ip = XFS_I(inode);
if (!ip->i_rwtrace)
return;
ktrace_enter(ip->i_rwtrace,
(void *)((unsigned long)tag),
(void *)ip,
(void *)inode,
(void *)page,
(void *)pgoff,
(void *)((unsigned long)((ip->i_d.di_size >> 32) & 0xffffffff)),
(void *)((unsigned long)(ip->i_d.di_size & 0xffffffff)),
(void *)((unsigned long)((isize >> 32) & 0xffffffff)),
(void *)((unsigned long)(isize & 0xffffffff)),
(void *)((unsigned long)((offset >> 32) & 0xffffffff)),
(void *)((unsigned long)(offset & 0xffffffff)),
(void *)((unsigned long)delalloc),
(void *)((unsigned long)unmapped),
(void *)((unsigned long)unwritten),
(void *)((unsigned long)current_pid()),
(void *)NULL);
}
#else
#define xfs_page_trace(tag, inode, page, pgoff)
#endif
STATIC struct block_device *
xfs_find_bdev_for_inode(
struct xfs_inode *ip)
{
struct xfs_mount *mp = ip->i_mount;
if (XFS_IS_REALTIME_INODE(ip))
return mp->m_rtdev_targp->bt_bdev;
else
return mp->m_ddev_targp->bt_bdev;
}
/*
* Schedule IO completion handling on a xfsdatad if this was
* the final hold on this ioend. If we are asked to wait,
* flush the workqueue.
*/
STATIC void
xfs_finish_ioend(
xfs_ioend_t *ioend,
int wait)
{
if (atomic_dec_and_test(&ioend->io_remaining)) {
queue_work(xfsdatad_workqueue, &ioend->io_work);
if (wait)
flush_workqueue(xfsdatad_workqueue);
}
}
/*
* We're now finished for good with this ioend structure.
* Update the page state via the associated buffer_heads,
* release holds on the inode and bio, and finally free
* up memory. Do not use the ioend after this.
*/
STATIC void
xfs_destroy_ioend(
xfs_ioend_t *ioend)
{
struct buffer_head *bh, *next;
for (bh = ioend->io_buffer_head; bh; bh = next) {
next = bh->b_private;
bh->b_end_io(bh, !ioend->io_error);
}
if (unlikely(ioend->io_error)) {
vn_ioerror(XFS_I(ioend->io_inode), ioend->io_error,
__FILE__,__LINE__);
}
vn_iowake(XFS_I(ioend->io_inode));
mempool_free(ioend, xfs_ioend_pool);
}
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
/*
* Update on-disk file size now that data has been written to disk.
* The current in-memory file size is i_size. If a write is beyond
* eof i_new_size will be the intended file size until i_size is
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
* updated. If this write does not extend all the way to the valid
* file size then restrict this update to the end of the write.
*/
STATIC void
xfs_setfilesize(
xfs_ioend_t *ioend)
{
xfs_inode_t *ip = XFS_I(ioend->io_inode);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
xfs_fsize_t isize;
xfs_fsize_t bsize;
ASSERT((ip->i_d.di_mode & S_IFMT) == S_IFREG);
ASSERT(ioend->io_type != IOMAP_READ);
if (unlikely(ioend->io_error))
return;
bsize = ioend->io_offset + ioend->io_size;
xfs_ilock(ip, XFS_ILOCK_EXCL);
isize = MAX(ip->i_size, ip->i_new_size);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
isize = MIN(isize, bsize);
if (ip->i_d.di_size < isize) {
ip->i_d.di_size = isize;
ip->i_update_core = 1;
ip->i_update_size = 1;
mark_inode_dirty_sync(ioend->io_inode);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
}
xfs_iunlock(ip, XFS_ILOCK_EXCL);
}
/*
* Buffered IO write completion for delayed allocate extents.
*/
STATIC void
xfs_end_bio_delalloc(
struct work_struct *work)
{
xfs_ioend_t *ioend =
container_of(work, xfs_ioend_t, io_work);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
xfs_setfilesize(ioend);
xfs_destroy_ioend(ioend);
}
/*
* Buffered IO write completion for regular, written extents.
*/
STATIC void
xfs_end_bio_written(
struct work_struct *work)
{
xfs_ioend_t *ioend =
container_of(work, xfs_ioend_t, io_work);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
xfs_setfilesize(ioend);
xfs_destroy_ioend(ioend);
}
/*
* IO write completion for unwritten extents.
*
* Issue transactions to convert a buffer range from unwritten
* to written extents.
*/
STATIC void
xfs_end_bio_unwritten(
struct work_struct *work)
{
xfs_ioend_t *ioend =
container_of(work, xfs_ioend_t, io_work);
struct xfs_inode *ip = XFS_I(ioend->io_inode);
xfs_off_t offset = ioend->io_offset;
size_t size = ioend->io_size;
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
if (likely(!ioend->io_error)) {
if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
int error;
error = xfs_iomap_write_unwritten(ip, offset, size);
if (error)
ioend->io_error = error;
}
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
xfs_setfilesize(ioend);
}
xfs_destroy_ioend(ioend);
}
/*
* IO read completion for regular, written extents.
*/
STATIC void
xfs_end_bio_read(
struct work_struct *work)
{
xfs_ioend_t *ioend =
container_of(work, xfs_ioend_t, io_work);
xfs_destroy_ioend(ioend);
}
/*
* Allocate and initialise an IO completion structure.
* We need to track unwritten extent write completion here initially.
* We'll need to extend this for updating the ondisk inode size later
* (vs. incore size).
*/
STATIC xfs_ioend_t *
xfs_alloc_ioend(
struct inode *inode,
unsigned int type)
{
xfs_ioend_t *ioend;
ioend = mempool_alloc(xfs_ioend_pool, GFP_NOFS);
/*
* Set the count to 1 initially, which will prevent an I/O
* completion callback from happening before we have started
* all the I/O from calling the completion routine too early.
*/
atomic_set(&ioend->io_remaining, 1);
ioend->io_error = 0;
ioend->io_list = NULL;
ioend->io_type = type;
ioend->io_inode = inode;
ioend->io_buffer_head = NULL;
ioend->io_buffer_tail = NULL;
atomic_inc(&XFS_I(ioend->io_inode)->i_iocount);
ioend->io_offset = 0;
ioend->io_size = 0;
if (type == IOMAP_UNWRITTEN)
INIT_WORK(&ioend->io_work, xfs_end_bio_unwritten);
else if (type == IOMAP_DELAY)
INIT_WORK(&ioend->io_work, xfs_end_bio_delalloc);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
else if (type == IOMAP_READ)
INIT_WORK(&ioend->io_work, xfs_end_bio_read);
else
INIT_WORK(&ioend->io_work, xfs_end_bio_written);
return ioend;
}
STATIC int
xfs_map_blocks(
struct inode *inode,
loff_t offset,
ssize_t count,
xfs_iomap_t *mapp,
int flags)
{
xfs_inode_t *ip = XFS_I(inode);
int error, nmaps = 1;
error = xfs_iomap(ip, offset, count,
flags, mapp, &nmaps);
if (!error && (flags & (BMAPI_WRITE|BMAPI_ALLOCATE)))
xfs_iflags_set(ip, XFS_IMODIFIED);
return -error;
}
STATIC_INLINE int
xfs_iomap_valid(
xfs_iomap_t *iomapp,
loff_t offset)
{
return offset >= iomapp->iomap_offset &&
offset < iomapp->iomap_offset + iomapp->iomap_bsize;
}
/*
* BIO completion handler for buffered IO.
*/
STATIC void
xfs_end_bio(
struct bio *bio,
int error)
{
xfs_ioend_t *ioend = bio->bi_private;
ASSERT(atomic_read(&bio->bi_cnt) >= 1);
ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;
/* Toss bio and pass work off to an xfsdatad thread */
bio->bi_private = NULL;
bio->bi_end_io = NULL;
bio_put(bio);
xfs_finish_ioend(ioend, 0);
}
STATIC void
xfs_submit_ioend_bio(
xfs_ioend_t *ioend,
struct bio *bio)
{
atomic_inc(&ioend->io_remaining);
bio->bi_private = ioend;
bio->bi_end_io = xfs_end_bio;
submit_bio(WRITE, bio);
ASSERT(!bio_flagged(bio, BIO_EOPNOTSUPP));
bio_put(bio);
}
STATIC struct bio *
xfs_alloc_ioend_bio(
struct buffer_head *bh)
{
struct bio *bio;
int nvecs = bio_get_nr_vecs(bh->b_bdev);
do {
bio = bio_alloc(GFP_NOIO, nvecs);
nvecs >>= 1;
} while (!bio);
ASSERT(bio->bi_private == NULL);
bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio->bi_bdev = bh->b_bdev;
bio_get(bio);
return bio;
}
STATIC void
xfs_start_buffer_writeback(
struct buffer_head *bh)
{
ASSERT(buffer_mapped(bh));
ASSERT(buffer_locked(bh));
ASSERT(!buffer_delay(bh));
ASSERT(!buffer_unwritten(bh));
mark_buffer_async_write(bh);
set_buffer_uptodate(bh);
clear_buffer_dirty(bh);
}
STATIC void
xfs_start_page_writeback(
struct page *page,
int clear_dirty,
int buffers)
{
ASSERT(PageLocked(page));
ASSERT(!PageWriteback(page));
if (clear_dirty)
clear_page_dirty_for_io(page);
set_page_writeback(page);
unlock_page(page);
writeback: remove pages_skipped accounting in __block_write_full_page() Miklos Szeredi <miklos@szeredi.hu> and me identified a writeback bug: > The following strange behavior can be observed: > > 1. large file is written > 2. after 30 seconds, nr_dirty goes down by 1024 > 3. then for some time (< 30 sec) nothing happens (disk idle) > 4. then nr_dirty again goes down by 1024 > 5. repeat from 3. until whole file is written > > So basically a 4Mbyte chunk of the file is written every 30 seconds. > I'm quite sure this is not the intended behavior. It can be produced by the following test scheme: # cat bin/test-writeback.sh grep nr_dirty /proc/vmstat echo 1 > /proc/sys/fs/inode_debug dd if=/dev/zero of=/var/x bs=1K count=204800& while true; do grep nr_dirty /proc/vmstat; sleep 1; done # bin/test-writeback.sh nr_dirty 19207 nr_dirty 19207 nr_dirty 30924 204800+0 records in 204800+0 records out 209715200 bytes (210 MB) copied, 1.58363 seconds, 132 MB/s nr_dirty 47150 nr_dirty 47141 nr_dirty 47142 nr_dirty 47142 nr_dirty 47142 nr_dirty 47142 nr_dirty 47205 nr_dirty 47214 nr_dirty 47214 nr_dirty 47214 nr_dirty 47214 nr_dirty 47214 nr_dirty 47215 nr_dirty 47216 nr_dirty 47216 nr_dirty 47216 nr_dirty 47154 nr_dirty 47143 nr_dirty 47143 nr_dirty 47143 nr_dirty 47143 nr_dirty 47143 nr_dirty 47142 nr_dirty 47142 nr_dirty 47142 nr_dirty 47142 nr_dirty 47134 nr_dirty 47134 nr_dirty 47135 nr_dirty 47135 nr_dirty 47135 nr_dirty 46097 <== -1038 nr_dirty 46098 nr_dirty 46098 nr_dirty 46098 [...] nr_dirty 46091 nr_dirty 46092 nr_dirty 46092 nr_dirty 45069 <== -1023 nr_dirty 45056 nr_dirty 45056 nr_dirty 45056 [...] nr_dirty 37822 nr_dirty 36799 <== -1023 [...] nr_dirty 36781 nr_dirty 35758 <== -1023 [...] nr_dirty 34708 nr_dirty 33672 <== -1024 [...] nr_dirty 33692 nr_dirty 32669 <== -1023 % ls -li /var/x 847824 -rw-r--r-- 1 root root 200M 2007-08-12 04:12 /var/x % dmesg|grep 847824 # generated by a debug printk [ 529.263184] redirtied inode 847824 line 548 [ 564.250872] redirtied inode 847824 line 548 [ 594.272797] redirtied inode 847824 line 548 [ 629.231330] redirtied inode 847824 line 548 [ 659.224674] redirtied inode 847824 line 548 [ 689.219890] redirtied inode 847824 line 548 [ 724.226655] redirtied inode 847824 line 548 [ 759.198568] redirtied inode 847824 line 548 # line 548 in fs/fs-writeback.c: 543 if (wbc->pages_skipped != pages_skipped) { 544 /* 545 * writeback is not making progress due to locked 546 * buffers. Skip this inode for now. 547 */ 548 redirty_tail(inode); 549 } More debug efforts show that __block_write_full_page() never has the chance to call submit_bh() for that big dirty file: the buffer head is *clean*. So basicly no page io is issued by __block_write_full_page(), hence pages_skipped goes up. Also the comment in generic_sync_sb_inodes(): 544 /* 545 * writeback is not making progress due to locked 546 * buffers. Skip this inode for now. 547 */ and the comment in __block_write_full_page(): 1713 /* 1714 * The page was marked dirty, but the buffers were 1715 * clean. Someone wrote them back by hand with 1716 * ll_rw_block/submit_bh. A rare case. 1717 */ do not quite agree with each other. The page writeback should be skipped for 'locked buffer', but here it is 'clean buffer'! This patch fixes this bug. Though I'm not sure why __block_write_full_page() is called only to do nothing and who actually issued the writeback for us. This is the two possible new behaviors after the patch: 1) pretty nice: wait 30s and write ALL:) 2) not so good: - during the dd: ~16M - after 30s: ~4M - after 5s: ~4M - after 5s: ~176M The next patch will fix case (2). Cc: David Chinner <dgc@sgi.com> Cc: Ken Chen <kenchen@google.com> Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 10:30:42 +04:00
/* If no buffers on the page are to be written, finish it here */
if (!buffers)
end_page_writeback(page);
}
static inline int bio_add_buffer(struct bio *bio, struct buffer_head *bh)
{
return bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
}
/*
* Submit all of the bios for all of the ioends we have saved up, covering the
* initial writepage page and also any probed pages.
*
* Because we may have multiple ioends spanning a page, we need to start
* writeback on all the buffers before we submit them for I/O. If we mark the
* buffers as we got, then we can end up with a page that only has buffers
* marked async write and I/O complete on can occur before we mark the other
* buffers async write.
*
* The end result of this is that we trip a bug in end_page_writeback() because
* we call it twice for the one page as the code in end_buffer_async_write()
* assumes that all buffers on the page are started at the same time.
*
* The fix is two passes across the ioend list - one to start writeback on the
* buffer_heads, and then submit them for I/O on the second pass.
*/
STATIC void
xfs_submit_ioend(
xfs_ioend_t *ioend)
{
xfs_ioend_t *head = ioend;
xfs_ioend_t *next;
struct buffer_head *bh;
struct bio *bio;
sector_t lastblock = 0;
/* Pass 1 - start writeback */
do {
next = ioend->io_list;
for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
xfs_start_buffer_writeback(bh);
}
} while ((ioend = next) != NULL);
/* Pass 2 - submit I/O */
ioend = head;
do {
next = ioend->io_list;
bio = NULL;
for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
if (!bio) {
retry:
bio = xfs_alloc_ioend_bio(bh);
} else if (bh->b_blocknr != lastblock + 1) {
xfs_submit_ioend_bio(ioend, bio);
goto retry;
}
if (bio_add_buffer(bio, bh) != bh->b_size) {
xfs_submit_ioend_bio(ioend, bio);
goto retry;
}
lastblock = bh->b_blocknr;
}
if (bio)
xfs_submit_ioend_bio(ioend, bio);
xfs_finish_ioend(ioend, 0);
} while ((ioend = next) != NULL);
}
/*
* Cancel submission of all buffer_heads so far in this endio.
* Toss the endio too. Only ever called for the initial page
* in a writepage request, so only ever one page.
*/
STATIC void
xfs_cancel_ioend(
xfs_ioend_t *ioend)
{
xfs_ioend_t *next;
struct buffer_head *bh, *next_bh;
do {
next = ioend->io_list;
bh = ioend->io_buffer_head;
do {
next_bh = bh->b_private;
clear_buffer_async_write(bh);
unlock_buffer(bh);
} while ((bh = next_bh) != NULL);
vn_iowake(XFS_I(ioend->io_inode));
mempool_free(ioend, xfs_ioend_pool);
} while ((ioend = next) != NULL);
}
/*
* Test to see if we've been building up a completion structure for
* earlier buffers -- if so, we try to append to this ioend if we
* can, otherwise we finish off any current ioend and start another.
* Return true if we've finished the given ioend.
*/
STATIC void
xfs_add_to_ioend(
struct inode *inode,
struct buffer_head *bh,
xfs_off_t offset,
unsigned int type,
xfs_ioend_t **result,
int need_ioend)
{
xfs_ioend_t *ioend = *result;
if (!ioend || need_ioend || type != ioend->io_type) {
xfs_ioend_t *previous = *result;
ioend = xfs_alloc_ioend(inode, type);
ioend->io_offset = offset;
ioend->io_buffer_head = bh;
ioend->io_buffer_tail = bh;
if (previous)
previous->io_list = ioend;
*result = ioend;
} else {
ioend->io_buffer_tail->b_private = bh;
ioend->io_buffer_tail = bh;
}
bh->b_private = NULL;
ioend->io_size += bh->b_size;
}
STATIC void
xfs_map_buffer(
struct buffer_head *bh,
xfs_iomap_t *mp,
xfs_off_t offset,
uint block_bits)
{
sector_t bn;
ASSERT(mp->iomap_bn != IOMAP_DADDR_NULL);
bn = (mp->iomap_bn >> (block_bits - BBSHIFT)) +
((offset - mp->iomap_offset) >> block_bits);
ASSERT(bn || (mp->iomap_flags & IOMAP_REALTIME));
bh->b_blocknr = bn;
set_buffer_mapped(bh);
}
STATIC void
xfs_map_at_offset(
struct buffer_head *bh,
loff_t offset,
int block_bits,
xfs_iomap_t *iomapp)
{
ASSERT(!(iomapp->iomap_flags & IOMAP_HOLE));
ASSERT(!(iomapp->iomap_flags & IOMAP_DELAY));
lock_buffer(bh);
xfs_map_buffer(bh, iomapp, offset, block_bits);
bh->b_bdev = iomapp->iomap_target->bt_bdev;
set_buffer_mapped(bh);
clear_buffer_delay(bh);
clear_buffer_unwritten(bh);
}
/*
* Look for a page at index that is suitable for clustering.
*/
STATIC unsigned int
xfs_probe_page(
struct page *page,
unsigned int pg_offset,
int mapped)
{
int ret = 0;
if (PageWriteback(page))
return 0;
if (page->mapping && PageDirty(page)) {
if (page_has_buffers(page)) {
struct buffer_head *bh, *head;
bh = head = page_buffers(page);
do {
if (!buffer_uptodate(bh))
break;
if (mapped != buffer_mapped(bh))
break;
ret += bh->b_size;
if (ret >= pg_offset)
break;
} while ((bh = bh->b_this_page) != head);
} else
ret = mapped ? 0 : PAGE_CACHE_SIZE;
}
return ret;
}
STATIC size_t
xfs_probe_cluster(
struct inode *inode,
struct page *startpage,
struct buffer_head *bh,
struct buffer_head *head,
int mapped)
{
struct pagevec pvec;
pgoff_t tindex, tlast, tloff;
size_t total = 0;
int done = 0, i;
/* First sum forwards in this page */
do {
if (!buffer_uptodate(bh) || (mapped != buffer_mapped(bh)))
return total;
total += bh->b_size;
} while ((bh = bh->b_this_page) != head);
/* if we reached the end of the page, sum forwards in following pages */
tlast = i_size_read(inode) >> PAGE_CACHE_SHIFT;
tindex = startpage->index + 1;
/* Prune this back to avoid pathological behavior */
tloff = min(tlast, startpage->index + 64);
pagevec_init(&pvec, 0);
while (!done && tindex <= tloff) {
unsigned len = min_t(pgoff_t, PAGEVEC_SIZE, tlast - tindex + 1);
if (!pagevec_lookup(&pvec, inode->i_mapping, tindex, len))
break;
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
size_t pg_offset, pg_len = 0;
if (tindex == tlast) {
pg_offset =
i_size_read(inode) & (PAGE_CACHE_SIZE - 1);
if (!pg_offset) {
done = 1;
break;
}
} else
pg_offset = PAGE_CACHE_SIZE;
if (page->index == tindex && trylock_page(page)) {
pg_len = xfs_probe_page(page, pg_offset, mapped);
unlock_page(page);
}
if (!pg_len) {
done = 1;
break;
}
total += pg_len;
tindex++;
}
pagevec_release(&pvec);
cond_resched();
}
return total;
}
/*
* Test if a given page is suitable for writing as part of an unwritten
* or delayed allocate extent.
*/
STATIC int
xfs_is_delayed_page(
struct page *page,
unsigned int type)
{
if (PageWriteback(page))
return 0;
if (page->mapping && page_has_buffers(page)) {
struct buffer_head *bh, *head;
int acceptable = 0;
bh = head = page_buffers(page);
do {
if (buffer_unwritten(bh))
acceptable = (type == IOMAP_UNWRITTEN);
else if (buffer_delay(bh))
acceptable = (type == IOMAP_DELAY);
else if (buffer_dirty(bh) && buffer_mapped(bh))
acceptable = (type == IOMAP_NEW);
else
break;
} while ((bh = bh->b_this_page) != head);
if (acceptable)
return 1;
}
return 0;
}
/*
* Allocate & map buffers for page given the extent map. Write it out.
* except for the original page of a writepage, this is called on
* delalloc/unwritten pages only, for the original page it is possible
* that the page has no mapping at all.
*/
STATIC int
xfs_convert_page(
struct inode *inode,
struct page *page,
loff_t tindex,
xfs_iomap_t *mp,
xfs_ioend_t **ioendp,
struct writeback_control *wbc,
int startio,
int all_bh)
{
struct buffer_head *bh, *head;
xfs_off_t end_offset;
unsigned long p_offset;
unsigned int type;
int bbits = inode->i_blkbits;
int len, page_dirty;
int count = 0, done = 0, uptodate = 1;
xfs_off_t offset = page_offset(page);
if (page->index != tindex)
goto fail;
if (!trylock_page(page))
goto fail;
if (PageWriteback(page))
goto fail_unlock_page;
if (page->mapping != inode->i_mapping)
goto fail_unlock_page;
if (!xfs_is_delayed_page(page, (*ioendp)->io_type))
goto fail_unlock_page;
/*
* page_dirty is initially a count of buffers on the page before
* EOF and is decremented as we move each into a cleanable state.
*
* Derivation:
*
* End offset is the highest offset that this page should represent.
* If we are on the last page, (end_offset & (PAGE_CACHE_SIZE - 1))
* will evaluate non-zero and be less than PAGE_CACHE_SIZE and
* hence give us the correct page_dirty count. On any other page,
* it will be zero and in that case we need page_dirty to be the
* count of buffers on the page.
*/
end_offset = min_t(unsigned long long,
(xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT,
i_size_read(inode));
len = 1 << inode->i_blkbits;
p_offset = min_t(unsigned long, end_offset & (PAGE_CACHE_SIZE - 1),
PAGE_CACHE_SIZE);
p_offset = p_offset ? roundup(p_offset, len) : PAGE_CACHE_SIZE;
page_dirty = p_offset / len;
bh = head = page_buffers(page);
do {
if (offset >= end_offset)
break;
if (!buffer_uptodate(bh))
uptodate = 0;
if (!(PageUptodate(page) || buffer_uptodate(bh))) {
done = 1;
continue;
}
if (buffer_unwritten(bh) || buffer_delay(bh)) {
if (buffer_unwritten(bh))
type = IOMAP_UNWRITTEN;
else
type = IOMAP_DELAY;
if (!xfs_iomap_valid(mp, offset)) {
done = 1;
continue;
}
ASSERT(!(mp->iomap_flags & IOMAP_HOLE));
ASSERT(!(mp->iomap_flags & IOMAP_DELAY));
xfs_map_at_offset(bh, offset, bbits, mp);
if (startio) {
xfs_add_to_ioend(inode, bh, offset,
type, ioendp, done);
} else {
set_buffer_dirty(bh);
unlock_buffer(bh);
mark_buffer_dirty(bh);
}
page_dirty--;
count++;
} else {
type = IOMAP_NEW;
if (buffer_mapped(bh) && all_bh && startio) {
lock_buffer(bh);
xfs_add_to_ioend(inode, bh, offset,
type, ioendp, done);
count++;
page_dirty--;
} else {
done = 1;
}
}
} while (offset += len, (bh = bh->b_this_page) != head);
if (uptodate && bh == head)
SetPageUptodate(page);
if (startio) {
if (count) {
struct backing_dev_info *bdi;
bdi = inode->i_mapping->backing_dev_info;
wbc->nr_to_write--;
if (bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
done = 1;
} else if (wbc->nr_to_write <= 0) {
done = 1;
}
}
xfs_start_page_writeback(page, !page_dirty, count);
}
return done;
fail_unlock_page:
unlock_page(page);
fail:
return 1;
}
/*
* Convert & write out a cluster of pages in the same extent as defined
* by mp and following the start page.
*/
STATIC void
xfs_cluster_write(
struct inode *inode,
pgoff_t tindex,
xfs_iomap_t *iomapp,
xfs_ioend_t **ioendp,
struct writeback_control *wbc,
int startio,
int all_bh,
pgoff_t tlast)
{
struct pagevec pvec;
int done = 0, i;
pagevec_init(&pvec, 0);
while (!done && tindex <= tlast) {
unsigned len = min_t(pgoff_t, PAGEVEC_SIZE, tlast - tindex + 1);
if (!pagevec_lookup(&pvec, inode->i_mapping, tindex, len))
break;
for (i = 0; i < pagevec_count(&pvec); i++) {
done = xfs_convert_page(inode, pvec.pages[i], tindex++,
iomapp, ioendp, wbc, startio, all_bh);
if (done)
break;
}
pagevec_release(&pvec);
cond_resched();
}
}
/*
* Calling this without startio set means we are being asked to make a dirty
* page ready for freeing it's buffers. When called with startio set then
* we are coming from writepage.
*
* When called with startio set it is important that we write the WHOLE
* page if possible.
* The bh->b_state's cannot know if any of the blocks or which block for
* that matter are dirty due to mmap writes, and therefore bh uptodate is
* only valid if the page itself isn't completely uptodate. Some layers
* may clear the page dirty flag prior to calling write page, under the
* assumption the entire page will be written out; by not writing out the
* whole page the page can be reused before all valid dirty data is
* written out. Note: in the case of a page that has been dirty'd by
* mapwrite and but partially setup by block_prepare_write the
* bh->b_states's will not agree and only ones setup by BPW/BCW will have
* valid state, thus the whole page must be written out thing.
*/
STATIC int
xfs_page_state_convert(
struct inode *inode,
struct page *page,
struct writeback_control *wbc,
int startio,
int unmapped) /* also implies page uptodate */
{
struct buffer_head *bh, *head;
xfs_iomap_t iomap;
xfs_ioend_t *ioend = NULL, *iohead = NULL;
loff_t offset;
unsigned long p_offset = 0;
unsigned int type;
__uint64_t end_offset;
pgoff_t end_index, last_index, tlast;
ssize_t size, len;
int flags, err, iomap_valid = 0, uptodate = 1;
int page_dirty, count = 0;
int trylock = 0;
int all_bh = unmapped;
if (startio) {
if (wbc->sync_mode == WB_SYNC_NONE && wbc->nonblocking)
trylock |= BMAPI_TRYLOCK;
}
/* Is this page beyond the end of the file? */
offset = i_size_read(inode);
end_index = offset >> PAGE_CACHE_SHIFT;
last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
if (page->index >= end_index) {
if ((page->index >= end_index + 1) ||
!(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) {
if (startio)
unlock_page(page);
return 0;
}
}
/*
* page_dirty is initially a count of buffers on the page before
* EOF and is decremented as we move each into a cleanable state.
*
* Derivation:
*
* End offset is the highest offset that this page should represent.
* If we are on the last page, (end_offset & (PAGE_CACHE_SIZE - 1))
* will evaluate non-zero and be less than PAGE_CACHE_SIZE and
* hence give us the correct page_dirty count. On any other page,
* it will be zero and in that case we need page_dirty to be the
* count of buffers on the page.
*/
end_offset = min_t(unsigned long long,
(xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT, offset);
len = 1 << inode->i_blkbits;
p_offset = min_t(unsigned long, end_offset & (PAGE_CACHE_SIZE - 1),
PAGE_CACHE_SIZE);
p_offset = p_offset ? roundup(p_offset, len) : PAGE_CACHE_SIZE;
page_dirty = p_offset / len;
bh = head = page_buffers(page);
offset = page_offset(page);
flags = BMAPI_READ;
type = IOMAP_NEW;
/* TODO: cleanup count and page_dirty */
do {
if (offset >= end_offset)
break;
if (!buffer_uptodate(bh))
uptodate = 0;
if (!(PageUptodate(page) || buffer_uptodate(bh)) && !startio) {
/*
* the iomap is actually still valid, but the ioend
* isn't. shouldn't happen too often.
*/
iomap_valid = 0;
continue;
}
if (iomap_valid)
iomap_valid = xfs_iomap_valid(&iomap, offset);
/*
* First case, map an unwritten extent and prepare for
* extent state conversion transaction on completion.
*
* Second case, allocate space for a delalloc buffer.
* We can return EAGAIN here in the release page case.
*
* Third case, an unmapped buffer was found, and we are
* in a path where we need to write the whole page out.
*/
if (buffer_unwritten(bh) || buffer_delay(bh) ||
((buffer_uptodate(bh) || PageUptodate(page)) &&
!buffer_mapped(bh) && (unmapped || startio))) {
int new_ioend = 0;
/*
* Make sure we don't use a read-only iomap
*/
if (flags == BMAPI_READ)
iomap_valid = 0;
if (buffer_unwritten(bh)) {
type = IOMAP_UNWRITTEN;
flags = BMAPI_WRITE | BMAPI_IGNSTATE;
} else if (buffer_delay(bh)) {
type = IOMAP_DELAY;
flags = BMAPI_ALLOCATE | trylock;
} else {
type = IOMAP_NEW;
flags = BMAPI_WRITE | BMAPI_MMAP;
}
if (!iomap_valid) {
/*
* if we didn't have a valid mapping then we
* need to ensure that we put the new mapping
* in a new ioend structure. This needs to be
* done to ensure that the ioends correctly
* reflect the block mappings at io completion
* for unwritten extent conversion.
*/
new_ioend = 1;
if (type == IOMAP_NEW) {
size = xfs_probe_cluster(inode,
page, bh, head, 0);
} else {
size = len;
}
err = xfs_map_blocks(inode, offset, size,
&iomap, flags);
if (err)
goto error;
iomap_valid = xfs_iomap_valid(&iomap, offset);
}
if (iomap_valid) {
xfs_map_at_offset(bh, offset,
inode->i_blkbits, &iomap);
if (startio) {
xfs_add_to_ioend(inode, bh, offset,
type, &ioend,
new_ioend);
} else {
set_buffer_dirty(bh);
unlock_buffer(bh);
mark_buffer_dirty(bh);
}
page_dirty--;
count++;
}
} else if (buffer_uptodate(bh) && startio) {
/*
* we got here because the buffer is already mapped.
* That means it must already have extents allocated
* underneath it. Map the extent by reading it.
*/
if (!iomap_valid || flags != BMAPI_READ) {
flags = BMAPI_READ;
size = xfs_probe_cluster(inode, page, bh,
head, 1);
err = xfs_map_blocks(inode, offset, size,
&iomap, flags);
if (err)
goto error;
iomap_valid = xfs_iomap_valid(&iomap, offset);
}
/*
* We set the type to IOMAP_NEW in case we are doing a
* small write at EOF that is extending the file but
* without needing an allocation. We need to update the
* file size on I/O completion in this case so it is
* the same case as having just allocated a new extent
* that we are writing into for the first time.
*/
type = IOMAP_NEW;
if (trylock_buffer(bh)) {
ASSERT(buffer_mapped(bh));
if (iomap_valid)
all_bh = 1;
xfs_add_to_ioend(inode, bh, offset, type,
&ioend, !iomap_valid);
page_dirty--;
count++;
} else {
iomap_valid = 0;
}
} else if ((buffer_uptodate(bh) || PageUptodate(page)) &&
(unmapped || startio)) {
iomap_valid = 0;
}
if (!iohead)
iohead = ioend;
} while (offset += len, ((bh = bh->b_this_page) != head));
if (uptodate && bh == head)
SetPageUptodate(page);
if (startio)
xfs_start_page_writeback(page, 1, count);
if (ioend && iomap_valid) {
offset = (iomap.iomap_offset + iomap.iomap_bsize - 1) >>
PAGE_CACHE_SHIFT;
tlast = min_t(pgoff_t, offset, last_index);
xfs_cluster_write(inode, page->index + 1, &iomap, &ioend,
wbc, startio, all_bh, tlast);
}
if (iohead)
xfs_submit_ioend(iohead);
return page_dirty;
error:
if (iohead)
xfs_cancel_ioend(iohead);
/*
* If it's delalloc and we have nowhere to put it,
* throw it away, unless the lower layers told
* us to try again.
*/
if (err != -EAGAIN) {
if (!unmapped)
block_invalidatepage(page, 0);
ClearPageUptodate(page);
}
return err;
}
/*
* writepage: Called from one of two places:
*
* 1. we are flushing a delalloc buffer head.
*
* 2. we are writing out a dirty page. Typically the page dirty
* state is cleared before we get here. In this case is it
* conceivable we have no buffer heads.
*
* For delalloc space on the page we need to allocate space and
* flush it. For unmapped buffer heads on the page we should
* allocate space if the page is uptodate. For any other dirty
* buffer heads on the page we should flush them.
*
* If we detect that a transaction would be required to flush
* the page, we have to check the process flags first, if we
* are already in a transaction or disk I/O during allocations
* is off, we need to fail the writepage and redirty the page.
*/
STATIC int
xfs_vm_writepage(
struct page *page,
struct writeback_control *wbc)
{
int error;
int need_trans;
int delalloc, unmapped, unwritten;
struct inode *inode = page->mapping->host;
xfs_page_trace(XFS_WRITEPAGE_ENTER, inode, page, 0);
/*
* We need a transaction if:
* 1. There are delalloc buffers on the page
* 2. The page is uptodate and we have unmapped buffers
* 3. The page is uptodate and we have no buffers
* 4. There are unwritten buffers on the page
*/
if (!page_has_buffers(page)) {
unmapped = 1;
need_trans = 1;
} else {
xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);
if (!PageUptodate(page))
unmapped = 0;
need_trans = delalloc + unmapped + unwritten;
}
/*
* If we need a transaction and the process flags say
* we are already in a transaction, or no IO is allowed
* then mark the page dirty again and leave the page
* as is.
*/
if (current_test_flags(PF_FSTRANS) && need_trans)
goto out_fail;
/*
* Delay hooking up buffer heads until we have
* made our go/no-go decision.
*/
if (!page_has_buffers(page))
create_empty_buffers(page, 1 << inode->i_blkbits, 0);
/*
* Convert delayed allocate, unwritten or unmapped space
* to real space and flush out to disk.
*/
error = xfs_page_state_convert(inode, page, wbc, 1, unmapped);
if (error == -EAGAIN)
goto out_fail;
if (unlikely(error < 0))
goto out_unlock;
return 0;
out_fail:
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return 0;
out_unlock:
unlock_page(page);
return error;
}
STATIC int
xfs_vm_writepages(
struct address_space *mapping,
struct writeback_control *wbc)
{
xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
return generic_writepages(mapping, wbc);
}
/*
* Called to move a page into cleanable state - and from there
* to be released. Possibly the page is already clean. We always
* have buffer heads in this call.
*
* Returns 0 if the page is ok to release, 1 otherwise.
*
* Possible scenarios are:
*
* 1. We are being called to release a page which has been written
* to via regular I/O. buffer heads will be dirty and possibly
* delalloc. If no delalloc buffer heads in this case then we
* can just return zero.
*
* 2. We are called to release a page which has been written via
* mmap, all we need to do is ensure there is no delalloc
* state in the buffer heads, if not we can let the caller
* free them and we should come back later via writepage.
*/
STATIC int
xfs_vm_releasepage(
struct page *page,
gfp_t gfp_mask)
{
struct inode *inode = page->mapping->host;
int dirty, delalloc, unmapped, unwritten;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_ALL,
.nr_to_write = 1,
};
xfs_page_trace(XFS_RELEASEPAGE_ENTER, inode, page, 0);
if (!page_has_buffers(page))
return 0;
xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);
if (!delalloc && !unwritten)
goto free_buffers;
if (!(gfp_mask & __GFP_FS))
return 0;
/* If we are already inside a transaction or the thread cannot
* do I/O, we cannot release this page.
*/
if (current_test_flags(PF_FSTRANS))
return 0;
/*
* Convert delalloc space to real space, do not flush the
* data out to disk, that will be done by the caller.
* Never need to allocate space here - we will always
* come back to writepage in that case.
*/
dirty = xfs_page_state_convert(inode, page, &wbc, 0, 0);
if (dirty == 0 && !unwritten)
goto free_buffers;
return 0;
free_buffers:
return try_to_free_buffers(page);
}
STATIC int
__xfs_get_blocks(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create,
int direct,
bmapi_flags_t flags)
{
xfs_iomap_t iomap;
xfs_off_t offset;
ssize_t size;
int niomap = 1;
int error;
offset = (xfs_off_t)iblock << inode->i_blkbits;
ASSERT(bh_result->b_size >= (1 << inode->i_blkbits));
size = bh_result->b_size;
error = xfs_iomap(XFS_I(inode), offset, size,
create ? flags : BMAPI_READ, &iomap, &niomap);
if (error)
return -error;
if (niomap == 0)
return 0;
if (iomap.iomap_bn != IOMAP_DADDR_NULL) {
/*
* For unwritten extents do not report a disk address on
* the read case (treat as if we're reading into a hole).
*/
if (create || !(iomap.iomap_flags & IOMAP_UNWRITTEN)) {
xfs_map_buffer(bh_result, &iomap, offset,
inode->i_blkbits);
}
if (create && (iomap.iomap_flags & IOMAP_UNWRITTEN)) {
if (direct)
bh_result->b_private = inode;
set_buffer_unwritten(bh_result);
}
}
/*
* If this is a realtime file, data may be on a different device.
* to that pointed to from the buffer_head b_bdev currently.
*/
bh_result->b_bdev = iomap.iomap_target->bt_bdev;
/*
* If we previously allocated a block out beyond eof and we are now
* coming back to use it then we will need to flag it as new even if it
* has a disk address.
*
* With sub-block writes into unwritten extents we also need to mark
* the buffer as new so that the unwritten parts of the buffer gets
* correctly zeroed.
*/
if (create &&
((!buffer_mapped(bh_result) && !buffer_uptodate(bh_result)) ||
(offset >= i_size_read(inode)) ||
(iomap.iomap_flags & (IOMAP_NEW|IOMAP_UNWRITTEN))))
set_buffer_new(bh_result);
if (iomap.iomap_flags & IOMAP_DELAY) {
BUG_ON(direct);
if (create) {
set_buffer_uptodate(bh_result);
set_buffer_mapped(bh_result);
set_buffer_delay(bh_result);
}
}
if (direct || size > (1 << inode->i_blkbits)) {
ASSERT(iomap.iomap_bsize - iomap.iomap_delta > 0);
offset = min_t(xfs_off_t,
iomap.iomap_bsize - iomap.iomap_delta, size);
bh_result->b_size = (ssize_t)min_t(xfs_off_t, LONG_MAX, offset);
}
return 0;
}
int
xfs_get_blocks(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create)
{
return __xfs_get_blocks(inode, iblock,
bh_result, create, 0, BMAPI_WRITE);
}
STATIC int
xfs_get_blocks_direct(
struct inode *inode,
sector_t iblock,
struct buffer_head *bh_result,
int create)
{
return __xfs_get_blocks(inode, iblock,
bh_result, create, 1, BMAPI_WRITE|BMAPI_DIRECT);
}
STATIC void
xfs_end_io_direct(
struct kiocb *iocb,
loff_t offset,
ssize_t size,
void *private)
{
xfs_ioend_t *ioend = iocb->private;
/*
* Non-NULL private data means we need to issue a transaction to
* convert a range from unwritten to written extents. This needs
* to happen from process context but aio+dio I/O completion
* happens from irq context so we need to defer it to a workqueue.
* This is not necessary for synchronous direct I/O, but we do
* it anyway to keep the code uniform and simpler.
*
* Well, if only it were that simple. Because synchronous direct I/O
* requires extent conversion to occur *before* we return to userspace,
* we have to wait for extent conversion to complete. Look at the
* iocb that has been passed to us to determine if this is AIO or
* not. If it is synchronous, tell xfs_finish_ioend() to kick the
* workqueue and wait for it to complete.
*
* The core direct I/O code might be changed to always call the
* completion handler in the future, in which case all this can
* go away.
*/
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
ioend->io_offset = offset;
ioend->io_size = size;
if (ioend->io_type == IOMAP_READ) {
xfs_finish_ioend(ioend, 0);
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
} else if (private && size > 0) {
xfs_finish_ioend(ioend, is_sync_kiocb(iocb));
} else {
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
/*
* A direct I/O write ioend starts it's life in unwritten
* state in case they map an unwritten extent. This write
* didn't map an unwritten extent so switch it's completion
* handler.
*/
INIT_WORK(&ioend->io_work, xfs_end_bio_written);
xfs_finish_ioend(ioend, 0);
}
/*
* blockdev_direct_IO can return an error even after the I/O
* completion handler was called. Thus we need to protect
* against double-freeing.
*/
iocb->private = NULL;
}
STATIC ssize_t
xfs_vm_direct_IO(
int rw,
struct kiocb *iocb,
const struct iovec *iov,
loff_t offset,
unsigned long nr_segs)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
struct block_device *bdev;
ssize_t ret;
bdev = xfs_find_bdev_for_inode(XFS_I(inode));
if (rw == WRITE) {
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
iocb->private = xfs_alloc_ioend(inode, IOMAP_UNWRITTEN);
ret = blockdev_direct_IO_own_locking(rw, iocb, inode,
bdev, iov, offset, nr_segs,
xfs_get_blocks_direct,
xfs_end_io_direct);
} else {
[XFS] Fix to prevent the notorious 'NULL files' problem after a crash. The problem that has been addressed is that of synchronising updates of the file size with writes that extend a file. Without the fix the update of a file's size, as a result of a write beyond eof, is independent of when the cached data is flushed to disk. Often the file size update would be written to the filesystem log before the data is flushed to disk. When a system crashes between these two events and the filesystem log is replayed on mount the file's size will be set but since the contents never made it to disk the file is full of holes. If some of the cached data was flushed to disk then it may just be a section of the file at the end that has holes. There are existing fixes to help alleviate this problem, particularly in the case where a file has been truncated, that force cached data to be flushed to disk when the file is closed. If the system crashes while the file(s) are still open then this flushing will never occur. The fix that we have implemented is to introduce a second file size, called the in-memory file size, that represents the current file size as viewed by the user. The existing file size, called the on-disk file size, is the one that get's written to the filesystem log and we only update it when it is safe to do so. When we write to a file beyond eof we only update the in- memory file size in the write operation. Later when the I/O operation, that flushes the cached data to disk completes, an I/O completion routine will update the on-disk file size. The on-disk file size will be updated to the maximum offset of the I/O or to the value of the in-memory file size if the I/O includes eof. SGI-PV: 958522 SGI-Modid: xfs-linux-melb:xfs-kern:28322a Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
2007-05-08 07:49:46 +04:00
iocb->private = xfs_alloc_ioend(inode, IOMAP_READ);
ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
bdev, iov, offset, nr_segs,
xfs_get_blocks_direct,
xfs_end_io_direct);
}
[PATCH] dio: only call aio_complete() after returning -EIOCBQUEUED The only time it is safe to call aio_complete() is when the ->ki_retry function returns -EIOCBQUEUED to the AIO core. direct_io_worker() has historically done this by relying on its caller to translate positive return codes into -EIOCBQUEUED for the aio case. It did this by trying to keep conditionals in sync. direct_io_worker() knew when finished_one_bio() was going to call aio_complete(). It would reverse the test and wait and free the dio in the cases it thought that finished_one_bio() wasn't going to. Not surprisingly, it ended up getting it wrong. 'ret' could be a negative errno from the submission path but it failed to communicate this to finished_one_bio(). direct_io_worker() would return < 0, it's callers wouldn't raise -EIOCBQUEUED, and aio_complete() would be called. In the future finished_one_bio()'s tests wouldn't reflect this and aio_complete() would be called for a second time which can manifest as an oops. The previous cleanups have whittled the sync and async completion paths down to the point where we can collapse them and clearly reassert the invariant that we must only call aio_complete() after returning -EIOCBQUEUED. direct_io_worker() will only return -EIOCBQUEUED when it is not the last to drop the dio refcount and the aio bio completion path will only call aio_complete() when it is the last to drop the dio refcount. direct_io_worker() can ensure that it is the last to drop the reference count by waiting for bios to drain. It does this for sync ops, of course, and for partial dio writes that must fall back to buffered and for aio ops that saw errors during submission. This means that operations that end up waiting, even if they were issued as aio ops, will not call aio_complete() from dio. Instead we return the return code of the operation and let the aio core call aio_complete(). This is purposely done to fix a bug where AIO DIO file extensions would call aio_complete() before their callers have a chance to update i_size. Now that direct_io_worker() is explicitly returning -EIOCBQUEUED its callers no longer have to translate for it. XFS needs to be careful not to free resources that will be used during AIO completion if -EIOCBQUEUED is returned. We maintain the previous behaviour of trying to write fs metadata for O_SYNC aio+dio writes. Signed-off-by: Zach Brown <zach.brown@oracle.com> Cc: Badari Pulavarty <pbadari@us.ibm.com> Cc: Suparna Bhattacharya <suparna@in.ibm.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> Cc: <xfs-masters@oss.sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-10 13:21:05 +03:00
if (unlikely(ret != -EIOCBQUEUED && iocb->private))
xfs_destroy_ioend(iocb->private);
return ret;
}
STATIC int
xfs_vm_write_begin(
struct file *file,
struct address_space *mapping,
loff_t pos,
unsigned len,
unsigned flags,
struct page **pagep,
void **fsdata)
{
*pagep = NULL;
return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
xfs_get_blocks);
}
STATIC sector_t
xfs_vm_bmap(
struct address_space *mapping,
sector_t block)
{
struct inode *inode = (struct inode *)mapping->host;
struct xfs_inode *ip = XFS_I(inode);
xfs_itrace_entry(XFS_I(inode));
xfs_ilock(ip, XFS_IOLOCK_SHARED);
xfs_flush_pages(ip, (xfs_off_t)0, -1, 0, FI_REMAPF);
xfs_iunlock(ip, XFS_IOLOCK_SHARED);
return generic_block_bmap(mapping, block, xfs_get_blocks);
}
STATIC int
xfs_vm_readpage(
struct file *unused,
struct page *page)
{
return mpage_readpage(page, xfs_get_blocks);
}
STATIC int
xfs_vm_readpages(
struct file *unused,
struct address_space *mapping,
struct list_head *pages,
unsigned nr_pages)
{
return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
}
STATIC void
xfs_vm_invalidatepage(
struct page *page,
unsigned long offset)
{
xfs_page_trace(XFS_INVALIDPAGE_ENTER,
page->mapping->host, page, offset);
block_invalidatepage(page, offset);
}
const struct address_space_operations xfs_address_space_operations = {
.readpage = xfs_vm_readpage,
.readpages = xfs_vm_readpages,
.writepage = xfs_vm_writepage,
.writepages = xfs_vm_writepages,
.sync_page = block_sync_page,
.releasepage = xfs_vm_releasepage,
.invalidatepage = xfs_vm_invalidatepage,
.write_begin = xfs_vm_write_begin,
.write_end = generic_write_end,
.bmap = xfs_vm_bmap,
.direct_IO = xfs_vm_direct_IO,
.migratepage = buffer_migrate_page,
};