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author | Theodore Ts'o <tytso@mit.edu> | 2015-10-15 10:29:05 -0400 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2015-10-15 10:29:05 -0400 |
commit | b90197b655185a11640cce3a0a0bc5d8291b8ad2 (patch) | |
tree | 2fb6e2b7583eec3169d86d643f45b29d2704261b /fs/ext4/inode.c | |
parent | 36086d43f6575c081067de9855786a2fc91df77b (diff) | |
download | op-kernel-dev-b90197b655185a11640cce3a0a0bc5d8291b8ad2.zip op-kernel-dev-b90197b655185a11640cce3a0a0bc5d8291b8ad2.tar.gz |
ext4: use private version of page_zero_new_buffers() for data=journal mode
If there is a error while copying data from userspace into the page
cache during a write(2) system call, in data=journal mode, in
ext4_journalled_write_end() were using page_zero_new_buffers() from
fs/buffer.c. Unfortunately, this sets the buffer dirty flag, which is
no good if journalling is enabled. This is a long-standing bug that
goes back for years and years in ext3, but a combination of (a)
data=journal not being very common, (b) in many case it only results
in a warning message. and (c) only very rarely causes the kernel hang,
means that we only really noticed this as a problem when commit
998ef75ddb caused this failure to happen frequently enough to cause
generic/208 to fail when run in data=journal mode.
The fix is to have our own version of this function that doesn't call
mark_dirty_buffer(), since we will end up calling
ext4_handle_dirty_metadata() on the buffer head(s) in questions very
shortly afterwards in ext4_journalled_write_end().
Thanks to Dave Hansen and Linus Torvalds for helping to identify the
root cause of the problem.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.com>
Diffstat (limited to 'fs/ext4/inode.c')
-rw-r--r-- | fs/ext4/inode.c | 34 |
1 files changed, 33 insertions, 1 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index ae52e32..f205ac3 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1181,6 +1181,38 @@ errout: return ret ? ret : copied; } +/* + * This is a private version of page_zero_new_buffers() which doesn't + * set the buffer to be dirty, since in data=journalled mode we need + * to call ext4_handle_dirty_metadata() instead. + */ +static void zero_new_buffers(struct page *page, unsigned from, unsigned to) +{ + unsigned int block_start = 0, block_end; + struct buffer_head *head, *bh; + + bh = head = page_buffers(page); + do { + block_end = block_start + bh->b_size; + if (buffer_new(bh)) { + if (block_end > from && block_start < to) { + if (!PageUptodate(page)) { + unsigned start, size; + + start = max(from, block_start); + size = min(to, block_end) - start; + + zero_user(page, start, size); + set_buffer_uptodate(bh); + } + clear_buffer_new(bh); + } + } + block_start = block_end; + bh = bh->b_this_page; + } while (bh != head); +} + static int ext4_journalled_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, @@ -1207,7 +1239,7 @@ static int ext4_journalled_write_end(struct file *file, if (copied < len) { if (!PageUptodate(page)) copied = 0; - page_zero_new_buffers(page, from+copied, to); + zero_new_buffers(page, from+copied, to); } ret = ext4_walk_page_buffers(handle, page_buffers(page), from, |