Re: [PATCH v2] ext4:Fix WARNING in ext4_journalled_invalidate_folio

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The WARNING in ext4_journalled_invalidate_folio can still be triggered from ext4_write_begin on error paths.
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commit 83d8cc4138093c0b6b19db042eb3a85e72ca5b68
Author: shuo chen <1289151713@qq.com>

    ext4:Fix WARNING in ext4_journalled_invalidate_folio

This commit fixes a warning in ext4_journalled_invalidate_folio() by
calling ext4_wait_for_tail_page_commit() before truncating a failed write
in ext4_journalled_write_end(). This prevents invalidating the folio while
it is being committed.

Suggested-by: Jan Kara <jack@suse.cz>
Reported-by: Farhad Alemi <farhad.alemi@berkeley.edu>
Closes:https://lore.kernel.org/linux-ext4/CA+0ovCgxFN3TLpdS_O_Z48sARuQ-WR-JLDCqQWEmd9ELtkzddA@mail.gmail.com/T/
Signed-off-by: shuo chen <1289151713@qq.com>

> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 26f0f9714f03c..960a049a67bd2 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c

[ ... ]

> @@ -1597,6 +1598,7 @@ static int ext4_journalled_write_end(const struct kiocb *iocb,
>  	if (!ret)
>  		ret = ret2;
>  	if (pos + len > inode->i_size && !verity) {
> +		ext4_wait_for_tail_page_commit(inode);
>  		ext4_truncate_failed_write(inode);
>  		/*
>  		 * If truncate failed early the inode might still be

[Severity: High]
This isn't a bug introduced by this patch, but it appears the same issue
might still exist on the error paths in ext4_write_begin().

When a write fails (e.g., due to ENOSPC or block allocation failure) and
extends i_size on a data=journal file, does ext4_write_begin() also need
to wait for the tail page commit?

fs/ext4/inode.c:ext4_write_begin() {
	...
		ext4_journal_stop(handle);
		if (extended) {
			ext4_truncate_failed_write(inode);
	...
}

If ext4_truncate_failed_write() attempts to invalidate the folio without
waiting, jbd2_journal_invalidate_folio() could return -EBUSY because the
buffer is still committing. Could this leave the page cache in an
inconsistent state and trigger the WARN_ON in
ext4_journalled_invalidate_folio()?

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Sashiko AI review · https://sashiko.dev/#/patchset/tencent_87F5A404ED65B0B1349C60E830C485716705@qq.com?part=1