WSL2-Linux-Kernel/fs/iomap.c

498 строки
12 KiB
C

/*
* Copyright (C) 2010 Red Hat, Inc.
* Copyright (c) 2016 Christoph Hellwig.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will 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.
*/
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include "internal.h"
typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
void *data, struct iomap *iomap);
/*
* Execute a iomap write on a segment of the mapping that spans a
* contiguous range of pages that have identical block mapping state.
*
* This avoids the need to map pages individually, do individual allocations
* for each page and most importantly avoid the need for filesystem specific
* locking per page. Instead, all the operations are amortised over the entire
* range of pages. It is assumed that the filesystems will lock whatever
* resources they require in the iomap_begin call, and release them in the
* iomap_end call.
*/
static loff_t
iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
struct iomap_ops *ops, void *data, iomap_actor_t actor)
{
struct iomap iomap = { 0 };
loff_t written = 0, ret;
/*
* Need to map a range from start position for length bytes. This can
* span multiple pages - it is only guaranteed to return a range of a
* single type of pages (e.g. all into a hole, all mapped or all
* unwritten). Failure at this point has nothing to undo.
*
* If allocation is required for this range, reserve the space now so
* that the allocation is guaranteed to succeed later on. Once we copy
* the data into the page cache pages, then we cannot fail otherwise we
* expose transient stale data. If the reserve fails, we can safely
* back out at this point as there is nothing to undo.
*/
ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
if (ret)
return ret;
if (WARN_ON(iomap.offset > pos))
return -EIO;
/*
* Cut down the length to the one actually provided by the filesystem,
* as it might not be able to give us the whole size that we requested.
*/
if (iomap.offset + iomap.length < pos + length)
length = iomap.offset + iomap.length - pos;
/*
* Now that we have guaranteed that the space allocation will succeed.
* we can do the copy-in page by page without having to worry about
* failures exposing transient data.
*/
written = actor(inode, pos, length, data, &iomap);
/*
* Now the data has been copied, commit the range we've copied. This
* should not fail unless the filesystem has had a fatal error.
*/
ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0,
flags, &iomap);
return written ? written : ret;
}
static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
loff_t i_size = i_size_read(inode);
/*
* Only truncate newly allocated pages beyoned EOF, even if the
* write started inside the existing inode size.
*/
if (pos + len > i_size)
truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}
static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
struct page **pagep, struct iomap *iomap)
{
pgoff_t index = pos >> PAGE_SHIFT;
struct page *page;
int status = 0;
BUG_ON(pos + len > iomap->offset + iomap->length);
page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
if (!page)
return -ENOMEM;
status = __block_write_begin_int(page, pos, len, NULL, iomap);
if (unlikely(status)) {
unlock_page(page);
put_page(page);
page = NULL;
iomap_write_failed(inode, pos, len);
}
*pagep = page;
return status;
}
static int
iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
unsigned copied, struct page *page)
{
int ret;
ret = generic_write_end(NULL, inode->i_mapping, pos, len,
copied, page, NULL);
if (ret < len)
iomap_write_failed(inode, pos, len);
return ret;
}
static loff_t
iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
{
struct iov_iter *i = data;
long status = 0;
ssize_t written = 0;
unsigned int flags = AOP_FLAG_NOFS;
/*
* Copies from kernel address space cannot fail (NFSD is a big user).
*/
if (!iter_is_iovec(i))
flags |= AOP_FLAG_UNINTERRUPTIBLE;
do {
struct page *page;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
offset = (pos & (PAGE_SIZE - 1));
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_count(i));
again:
if (bytes > length)
bytes = length;
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*
* Not only is this an optimisation, but it is also required
* to check that the address is actually valid, when atomic
* usercopies are used, below.
*/
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
status = -EFAULT;
break;
}
status = iomap_write_begin(inode, pos, bytes, flags, &page,
iomap);
if (unlikely(status))
break;
if (mapping_writably_mapped(inode->i_mapping))
flush_dcache_page(page);
pagefault_disable();
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
pagefault_enable();
flush_dcache_page(page);
mark_page_accessed(page);
status = iomap_write_end(inode, pos, bytes, copied, page);
if (unlikely(status < 0))
break;
copied = status;
cond_resched();
iov_iter_advance(i, copied);
if (unlikely(copied == 0)) {
/*
* If we were unable to copy any data at all, we must
* fall back to a single segment length write.
*
* If we didn't fallback here, we could livelock
* because not all segments in the iov can be copied at
* once without a pagefault.
*/
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_single_seg_count(i));
goto again;
}
pos += copied;
written += copied;
length -= copied;
balance_dirty_pages_ratelimited(inode->i_mapping);
} while (iov_iter_count(i) && length);
return written ? written : status;
}
ssize_t
iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_ops *ops)
{
struct inode *inode = iocb->ki_filp->f_mapping->host;
loff_t pos = iocb->ki_pos, ret = 0, written = 0;
while (iov_iter_count(iter)) {
ret = iomap_apply(inode, pos, iov_iter_count(iter),
IOMAP_WRITE, ops, iter, iomap_write_actor);
if (ret <= 0)
break;
pos += ret;
written += ret;
}
return written ? written : ret;
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
unsigned bytes, struct iomap *iomap)
{
struct page *page;
int status;
status = iomap_write_begin(inode, pos, bytes,
AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
if (status)
return status;
zero_user(page, offset, bytes);
mark_page_accessed(page);
return iomap_write_end(inode, pos, bytes, bytes, page);
}
static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
struct iomap *iomap)
{
sector_t sector = iomap->blkno +
(((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);
return __dax_zero_page_range(iomap->bdev, sector, offset, bytes);
}
static loff_t
iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
void *data, struct iomap *iomap)
{
bool *did_zero = data;
loff_t written = 0;
int status;
/* already zeroed? we're done. */
if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
return count;
do {
unsigned offset, bytes;
offset = pos & (PAGE_SIZE - 1); /* Within page */
bytes = min_t(unsigned, PAGE_SIZE - offset, count);
if (IS_DAX(inode))
status = iomap_dax_zero(pos, offset, bytes, iomap);
else
status = iomap_zero(inode, pos, offset, bytes, iomap);
if (status < 0)
return status;
pos += bytes;
count -= bytes;
written += bytes;
if (did_zero)
*did_zero = true;
} while (count > 0);
return written;
}
int
iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
struct iomap_ops *ops)
{
loff_t ret;
while (len > 0) {
ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
ops, did_zero, iomap_zero_range_actor);
if (ret <= 0)
return ret;
pos += ret;
len -= ret;
}
return 0;
}
EXPORT_SYMBOL_GPL(iomap_zero_range);
int
iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
struct iomap_ops *ops)
{
unsigned blocksize = (1 << inode->i_blkbits);
unsigned off = pos & (blocksize - 1);
/* Block boundary? Nothing to do */
if (!off)
return 0;
return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
}
EXPORT_SYMBOL_GPL(iomap_truncate_page);
static loff_t
iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
void *data, struct iomap *iomap)
{
struct page *page = data;
int ret;
ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length,
NULL, iomap);
if (ret)
return ret;
block_commit_write(page, 0, length);
return length;
}
int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
struct iomap_ops *ops)
{
struct page *page = vmf->page;
struct inode *inode = file_inode(vma->vm_file);
unsigned long length;
loff_t offset, size;
ssize_t ret;
lock_page(page);
size = i_size_read(inode);
if ((page->mapping != inode->i_mapping) ||
(page_offset(page) > size)) {
/* We overload EFAULT to mean page got truncated */
ret = -EFAULT;
goto out_unlock;
}
/* page is wholly or partially inside EOF */
if (((page->index + 1) << PAGE_SHIFT) > size)
length = size & ~PAGE_MASK;
else
length = PAGE_SIZE;
offset = page_offset(page);
while (length > 0) {
ret = iomap_apply(inode, offset, length, IOMAP_WRITE,
ops, page, iomap_page_mkwrite_actor);
if (unlikely(ret <= 0))
goto out_unlock;
offset += ret;
length -= ret;
}
set_page_dirty(page);
wait_for_stable_page(page);
return 0;
out_unlock:
unlock_page(page);
return ret;
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
struct fiemap_ctx {
struct fiemap_extent_info *fi;
struct iomap prev;
};
static int iomap_to_fiemap(struct fiemap_extent_info *fi,
struct iomap *iomap, u32 flags)
{
switch (iomap->type) {
case IOMAP_HOLE:
/* skip holes */
return 0;
case IOMAP_DELALLOC:
flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
break;
case IOMAP_UNWRITTEN:
flags |= FIEMAP_EXTENT_UNWRITTEN;
break;
case IOMAP_MAPPED:
break;
}
return fiemap_fill_next_extent(fi, iomap->offset,
iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
iomap->length, flags | FIEMAP_EXTENT_MERGED);
}
static loff_t
iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
{
struct fiemap_ctx *ctx = data;
loff_t ret = length;
if (iomap->type == IOMAP_HOLE)
return length;
ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
ctx->prev = *iomap;
switch (ret) {
case 0: /* success */
return length;
case 1: /* extent array full */
return 0;
default:
return ret;
}
}
int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
loff_t start, loff_t len, struct iomap_ops *ops)
{
struct fiemap_ctx ctx;
loff_t ret;
memset(&ctx, 0, sizeof(ctx));
ctx.fi = fi;
ctx.prev.type = IOMAP_HOLE;
ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
if (ret)
return ret;
ret = filemap_write_and_wait(inode->i_mapping);
if (ret)
return ret;
while (len > 0) {
ret = iomap_apply(inode, start, len, 0, ops, &ctx,
iomap_fiemap_actor);
if (ret < 0)
return ret;
if (ret == 0)
break;
start += ret;
len -= ret;
}
if (ctx.prev.type != IOMAP_HOLE) {
ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
if (ret < 0)
return ret;
}
return 0;
}
EXPORT_SYMBOL_GPL(iomap_fiemap);