Commit fcf5ea10 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o

ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize

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: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
CC: stable@vger.kernel.org # 3.8+
parent e4510577
...@@ -537,6 +537,8 @@ static int ext4_find_unwritten_pgoff(struct inode *inode, ...@@ -537,6 +537,8 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
lastoff = page_offset(page); lastoff = page_offset(page);
bh = head = page_buffers(page); bh = head = page_buffers(page);
do { do {
if (lastoff + bh->b_size <= startoff)
goto next;
if (buffer_uptodate(bh) || if (buffer_uptodate(bh) ||
buffer_unwritten(bh)) { buffer_unwritten(bh)) {
if (whence == SEEK_DATA) if (whence == SEEK_DATA)
...@@ -551,6 +553,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode, ...@@ -551,6 +553,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
unlock_page(page); unlock_page(page);
goto out; goto out;
} }
next:
lastoff += bh->b_size; lastoff += bh->b_size;
bh = bh->b_this_page; bh = bh->b_this_page;
} while (bh != head); } while (bh != head);
......
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