Re: [PATCH] mm/filemap.c: fix criteria of calling iov_shorten() ingeneric_file_direct_write()

From: Jan Kara
Date: Wed Apr 24 2013 - 08:21:09 EST


On Tue 23-04-13 16:37:43, Gu Zheng wrote:
> From 35947e6535d92c54cf523470cc8811e8b5fee3e5 Mon Sep 17 00:00:00 2001
> From: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
> Date: Tue, 23 Apr 2013 16:09:04 +0800
> Subject: [PATCH] mm/filemap.c: fix criteria of calling iov_shorten() in generic_file_direct_write()
>
> generic_file_direct_write() compares 'count'(the max count we actually can write)
> with 'ocount'(the count we request to write) to see if there is need to call
> iov_shorten() to reduce number of segments and the iovec's length. If the
> 'count' is equal or greater than 'ocount', there is no need to call iov_shorten()
> indeed. So the judgement should be changed:
> 'if (count != ocount)' --> 'if (count < ocount)'
Thanks for the patch but it shouldn't be really possible that count >
ocount, should it? So your patch doesn't really fix anything. Or am I
missing something?

Honza
>
> Signed-off-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
> ---
> mm/filemap.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index e1979fd..c566b9c 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2183,7 +2183,7 @@ generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
> size_t write_len;
> pgoff_t end;
>
> - if (count != ocount)
> + if (count < ocount)
> *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
>
> write_len = iov_length(iov, *nr_segs);
> --
> 1.7.7
>
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--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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