Re: [PATCH] ext2: preserve completed DIO bytes when buffered fallback fails

[sashiko-bot@kernel.org]

> ext2_dio_write_iter() can complete part of a direct write before
> falling back to buffered I/O for a hole inside i_size. If
> generic_perform_write() then fails, its error overwrites the completed
> direct-I/O byte count.
> 
> For example, on a full filesystem, an 8 KiB write to a file with an
> allocated 4 KiB prefix and a 4 KiB hole overwrites the prefix but returns
> ENOSPC and leaves the file position unchanged. GNU dd with oflag=direct
> consequently reports zero bytes written.
> 
> Preserve a positive direct-I/O result and return the buffered error
> when no bytes were direct-written. This restores the fallback policy of
> generic_file_write_iter(), which ext2 used before its iomap conversion.
> 
> Fixes: fb5de4358e1a ("ext2: Move direct-io to use iomap")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>

Sashiko has reviewed this patch and found no issues.

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