On Fri 09-08-24 14:46:05, zhangshida wrote:
> From: Shida Zhang <zhangshida@xxxxxxxxxx>
>
> On an old kernel version(4.19, ext3, data=journal, pagesize=64k),
> an assertion failure will occasionally be triggered by the line below:
> -----------
> jbd2_journal_commit_transaction
> {
> ...
> J_ASSERT_BH(bh, !buffer_dirty(bh));
> /*
> * The buffer on BJ_Forget list and not jbddirty means
> ...
> }
> -----------
>
> The same condition may also be applied to the lattest kernel version.
Maybe let me shorten the following part of the changelog a bit:
When blocksize < pagesize and we truncate a file, there can be buffers in
the mapping tail page beyond i_size. These buffers will be filed to
transaction's BJ_Forget list by ext4_journalled_invalidatepage() during
truncation. When the transaction doing truncate starts committing, we can
grow the file again. This calls __block_write_begin() which allocates new
blocks under these buffers in the tail page we go through the branch:
if (buffer_new(bh)) {
clean_bdev_bh_alias(bh);
if (folio_test_uptodate(folio)) {
clear_buffer_new(bh);
set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
continue;
}
...
}
Hence buffers on BJ_Forget list of the committing transaction get marked
dirty and this triggers the jbd2 assertion.
Teach ext4_block_write_begin() to properly handle files with data
journalling by avoiding dirtying them directly. Instead of
folio_zero_new_buffers() we use ext4_journalled_zero_new_buffers() which
takes care of handling journalling. We also don't need to mark new uptodate
buffers as dirty in ext4_block_write_begin(). That will be either done
either by block_commit_write() in case of success or by
folio_zero_new_buffers() in case of failure.
> Reported-by: Baolin Liu <liubaolin@xxxxxxxxxx>
> Suggested-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Shida Zhang <zhangshida@xxxxxxxxxx>
> ---
> fs/ext4/inode.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 941c1c0d5c6e..de46c0a6842a 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -49,6 +49,11 @@
>
> #include <trace/events/ext4.h>
>
> +static void ext4_journalled_zero_new_buffers(handle_t *handle,
> + struct inode *inode,
> + struct folio *folio,
> + unsigned from, unsigned to);
> +
> static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
> struct ext4_inode_info *ei)
> {
> @@ -1042,7 +1047,8 @@ int do_journal_get_write_access(handle_t *handle, struct inode *inode,
> }
>
> #ifdef CONFIG_FS_ENCRYPTION
> -static int ext4_block_write_begin(struct folio *folio, loff_t pos, unsigned len,
> +static int ext4_block_write_begin(handle_t *handle, struct folio *folio,
> + loff_t pos, unsigned len,
> get_block_t *get_block)
> {
> unsigned from = pos & (PAGE_SIZE - 1);
> @@ -1056,6 +1062,7 @@ static int ext4_block_write_begin(struct folio *folio, loff_t pos, unsigned len,
> struct buffer_head *bh, *head, *wait[2];
> int nr_wait = 0;
> int i;
> + bool should_journal_data = ext4_should_journal_data(inode);
>
> BUG_ON(!folio_test_locked(folio));
> BUG_ON(from > PAGE_SIZE);
> @@ -1084,11 +1091,16 @@ static int ext4_block_write_begin(struct folio *folio, loff_t pos, unsigned len,
> err = get_block(inode, block, bh, 1);
> if (err)
> break;
> + if (should_journal_data)
> + do_journal_get_write_access(handle, inode, bh);
> if (buffer_new(bh)) {
> if (folio_test_uptodate(folio)) {
> clear_buffer_new(bh);
> set_buffer_uptodate(bh);
> - mark_buffer_dirty(bh);
> + if (should_journal_data)
> + ext4_dirty_journalled_data(handle, bh);
> + else
> + mark_buffer_dirty(bh);
This hunk is not needed. We can just do:
if (folio_test_uptodate(folio)) {
- clear_buffer_new(bh);
set_buffer_uptodate(bh);
- mark_buffer_dirty(bh);
continue;
}
> continue;
> }
> if (block_end > to || block_start < from)
> @@ -1118,7 +1130,11 @@ static int ext4_block_write_begin(struct folio *folio, loff_t pos, unsigned len,
> err = -EIO;
> }
> if (unlikely(err)) {
> - folio_zero_new_buffers(folio, from, to);
> + if (should_journal_data)
> + ext4_journalled_zero_new_buffers(handle, inode, folio,
> + from, to);
> + else
> + folio_zero_new_buffers(folio, from, to);
> } else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> for (i = 0; i < nr_wait; i++) {
> int err2;
This looks good.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
