Re: [PATCH v3] ext4: don't report delalloc data as a hole on indirect-mapped inodes

[sashiko-bot@kernel.org]

> When a plain lookup finds no block, ext4_ind_map_blocks() sizes the hole
> it reports by counting the empty subtrees under 'partial' in the on-disk
> indirect tree.  That count knows nothing about delayed allocation, so a
> range holding delalloc data that has not been written back yet is
> reported as a plain hole.  The extent-mapped path does not have this
> problem: it trims the hole it found at the first delayed extent before
> returning it.
> 
> ext4_map_blocks() consults the extent status tree before it calls into
> the mapping layer, so a query that starts exactly on the delayed block
> still finds it.  A query that starts earlier does not, because the hole
> reported for the earlier block already spans the delayed one.  On a
> 4k-block filesystem, lseek(SEEK_DATA) from offset 0 on a file whose only
> data block is at logical block N and is still dirty returns:
> 
> [ ... ]
> Reported-by: Alexander Monakov <amonakov@ispras.ru>
> Closes: https://lore.kernel.org/linux-ext4/594c17d9-c00f-e485-96fb-cedf27ce3aa3@ispras.ru/
> Suggested-by: Jan Kara <jack@suse.cz>
> Cc: stable@vger.kernel.org
> Signed-off-by: Daejun Park <daejun7.park@samsung.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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