| From fcf5ea10992fbac3c7473a1db33d56a139333cd1 Mon Sep 17 00:00:00 2001 |
| From: Jan Kara <jack@suse.cz> |
| Date: Sat, 5 Aug 2017 17:43:24 -0400 |
| Subject: ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/ext4/file.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/fs/ext4/file.c |
| +++ b/fs/ext4/file.c |
| @@ -500,6 +500,8 @@ static int ext4_find_unwritten_pgoff(str |
| 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) |
| @@ -514,6 +516,7 @@ static int ext4_find_unwritten_pgoff(str |
| unlock_page(page); |
| goto out; |
| } |
| +next: |
| lastoff += bh->b_size; |
| bh = bh->b_this_page; |
| } while (bh != head); |
