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SubjectRe: [PATCH] f2fs: fix retry logic in f2fs_write_cache_pages()
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On 2020/5/27 10:20, Sahitya Tummala wrote:
> In case a compressed file is getting overwritten, the current retry
> logic doesn't include the current page to be retried now as it sets
> the new start index as 0 and new end index as writeback_index - 1.
> This causes the corresponding cluster to be uncompressed and written
> as normal pages without compression. Fix this by allowing writeback to
> be retried for the current page as well (in case of compressed page
> getting retried due to index mismatch with cluster index). So that
> this cluster can be written compressed in case of overwrite.
>
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> ---
> fs/f2fs/data.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 4af5fcd..bfd1df4 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3024,7 +3024,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> if ((!cycled && !done) || retry) {

IMO, we add retry logic in wrong place, you can see that cycled value is
zero only if wbc->range_cyclic is true, in that case writeback_index is valid.

However if retry is true and wbc->range_cyclic is false, then writeback_index
would be uninitialized variable.

Thoughts?

Thanks,

> cycled = 1;
> index = 0;
> - end = writeback_index - 1;
> + end = retry ? -1 : writeback_index - 1;
> goto retry;
> }
> if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
>

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