| From | Willy Tarreau <> | Subject | [PATCH 3.10 041/139] ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize | Date | Wed, 1 Nov 2017 22:17:41 +0100 |
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From: Jan Kara <jack@suse.cz>
commit fcf5ea10992fbac3c7473a1db33d56a139333cd1 upstream.
ext4_find_unwritten_pgoff() does not properly handle a situation when starting index is in the middle of a page and blocksize < pagesize. The following command shows the bug on filesystem with 1k blocksize:
xfs_io -f -c "falloc 0 4k" \ -c "pwrite 1k 1k" \ -c "pwrite 3k 1k" \ -c "seek -a -r 0" foo
In this example, neither lseek(fd, 1024, SEEK_HOLE) nor lseek(fd, 2048, SEEK_DATA) will return the correct result.
Fix the problem by neglecting buffers in a page before starting offset.
Reported-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Jan Kara <jack@suse.cz> CC: stable@vger.kernel.org # 3.8+ Signed-off-by: Willy Tarreau <w@1wt.eu> --- fs/ext4/file.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index ec9770f..d490d6e 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -382,6 +382,8 @@ static int ext4_find_unwritten_pgoff(struct inode *inode, lastoff = page_offset(page); bh = head = page_buffers(page); do { + if (lastoff + bh->b_size <= startoff) + goto next; if (buffer_uptodate(bh) || buffer_unwritten(bh)) { if (whence == SEEK_DATA) @@ -396,6 +398,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode, unlock_page(page); goto out; } +next: lastoff += bh->b_size; bh = bh->b_this_page; } while (bh != head); -- 2.8.0.rc2.1.gbe9624a
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