From 53a2731f9310a66beaf55677229ab067c85ce4fa Mon Sep 17 00:00:00 2001 From: Michael Halcrow Date: Wed, 23 May 2007 13:58:15 -0700 Subject: [PATCH] eCryptfs: delay writing 0's after llseek until write Delay writing 0's out in eCryptfs after a seek past the end of the file until data is actually written. http://www.opengroup.org/onlinepubs/009695399/functions/lseek.html ``The lseek() function shall not, by itself, extend the size of a file.'' Without this fix, applications that lseek() past the end of the file without writing will experience unexpected behavior. Signed-off-by: Michael Halcrow Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ecryptfs/file.c | 59 +--------------------------------------------- fs/ecryptfs/mmap.c | 42 +++++++++++++++++++++++++++++---- 2 files changed, 38 insertions(+), 63 deletions(-) diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c index 9881b5c5de59..59288d817078 100644 --- a/fs/ecryptfs/file.c +++ b/fs/ecryptfs/file.c @@ -32,63 +32,6 @@ #include #include "ecryptfs_kernel.h" -/** - * ecryptfs_llseek - * @file: File we are seeking in - * @offset: The offset to seek to - * @origin: 2 - offset from i_size; 1 - offset from f_pos - * - * Returns the position we have seeked to, or negative on error - */ -static loff_t ecryptfs_llseek(struct file *file, loff_t offset, int origin) -{ - loff_t rv; - loff_t new_end_pos; - int rc; - int expanding_file = 0; - struct inode *inode = file->f_mapping->host; - - /* If our offset is past the end of our file, we're going to - * need to grow it so we have a valid length of 0's */ - new_end_pos = offset; - switch (origin) { - case 2: - new_end_pos += i_size_read(inode); - expanding_file = 1; - break; - case 1: - new_end_pos += file->f_pos; - if (new_end_pos > i_size_read(inode)) { - ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) " - "> i_size_read(inode)(=[0x%.16x])\n", - new_end_pos, i_size_read(inode)); - expanding_file = 1; - } - break; - default: - if (new_end_pos > i_size_read(inode)) { - ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) " - "> i_size_read(inode)(=[0x%.16x])\n", - new_end_pos, i_size_read(inode)); - expanding_file = 1; - } - } - ecryptfs_printk(KERN_DEBUG, "new_end_pos = [0x%.16x]\n", new_end_pos); - if (expanding_file) { - rc = ecryptfs_truncate(file->f_path.dentry, new_end_pos); - if (rc) { - rv = rc; - ecryptfs_printk(KERN_ERR, "Error on attempt to " - "truncate to (higher) offset [0x%.16x];" - " rc = [%d]\n", new_end_pos, rc); - goto out; - } - } - rv = generic_file_llseek(file, offset, origin); -out: - return rv; -} - /** * ecryptfs_read_update_atime * @@ -425,7 +368,7 @@ const struct file_operations ecryptfs_dir_fops = { }; const struct file_operations ecryptfs_main_fops = { - .llseek = ecryptfs_llseek, + .llseek = generic_file_llseek, .read = do_sync_read, .aio_read = ecryptfs_read_update_atime, .write = do_sync_write, diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c index 88ea6697908f..55cec98a84e7 100644 --- a/fs/ecryptfs/mmap.c +++ b/fs/ecryptfs/mmap.c @@ -376,8 +376,15 @@ out: return 0; } -static int ecryptfs_prepare_write(struct file *file, struct page *page, - unsigned from, unsigned to) +/** + * eCryptfs does not currently support holes. When writing after a + * seek past the end of the file, eCryptfs fills in 0's through to the + * current location. The code to fill in the 0's to all the + * intermediate pages calls ecryptfs_prepare_write_no_truncate(). + */ +static int +ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page, + unsigned from, unsigned to) { int rc = 0; @@ -390,6 +397,31 @@ out: return rc; } +static int ecryptfs_prepare_write(struct file *file, struct page *page, + unsigned from, unsigned to) +{ + loff_t pos; + int rc = 0; + + if (from == 0 && to == PAGE_CACHE_SIZE) + goto out; /* If we are writing a full page, it will be + up to date. */ + if (!PageUptodate(page)) + rc = ecryptfs_do_readpage(file, page, page->index); + pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; + if (pos > i_size_read(page->mapping->host)) { + rc = ecryptfs_truncate(file->f_path.dentry, pos); + if (rc) { + printk(KERN_ERR "Error on attempt to " + "truncate to (higher) offset [%lld];" + " rc = [%d]\n", pos, rc); + goto out; + } + } +out: + return rc; +} + int ecryptfs_writepage_and_release_lower_page(struct page *lower_page, struct inode *lower_inode, struct writeback_control *wbc) @@ -744,10 +776,10 @@ int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros) rc = PTR_ERR(tmp_page); goto out; } - rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros); - if (rc) { + if ((rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start, + (start + num_zeros)))) { ecryptfs_printk(KERN_ERR, "Error preparing to write zero's " - "to remainder of page at index [0x%.16x]\n", + "to page at index [0x%.16x]\n", index); page_cache_release(tmp_page); goto out;