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From: Ming Lei <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: [email protected], Jens Axboe <[email protected]>,
	Christoph Hellwig <[email protected]>,
	Matthew Wilcox <[email protected]>,
	Johannes Weiner <[email protected]>,
	Alexander Viro <[email protected]>,
	"Darrick J . Wong" <[email protected]>,
	"Martin K . Petersen" <[email protected]>,
	Jonathan Corbet <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], Christoph Hellwig <[email protected]>
Subject: Re: [PATCH v3 1/7] splice: don't generate zero-len segement bvecs
Date: Mon, 11 Jan 2021 10:48:35 +0800	[thread overview]
Message-ID: <20210111024835.GB4147870@T590> (raw)
In-Reply-To: <bfaeb54c88f0c962461b75c6493103e11bb0b17b.1610170479.git.asml.silence@gmail.com>

On Sat, Jan 09, 2021 at 04:02:57PM +0000, Pavel Begunkov wrote:
> iter_file_splice_write() may spawn bvec segments with zero-length. In
> preparation for prohibiting them, filter out by hand at splice level.
> 
> Reviewed-by: Christoph Hellwig <[email protected]>
> Signed-off-by: Pavel Begunkov <[email protected]>
> ---
>  fs/splice.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/splice.c b/fs/splice.c
> index 866d5c2367b2..474fb8b5562a 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -662,12 +662,14 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
>  
>  		/* build the vector */
>  		left = sd.total_len;
> -		for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++, n++) {
> +		for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) {
>  			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
>  			size_t this_len = buf->len;
>  
> -			if (this_len > left)
> -				this_len = left;
> +			/* zero-length bvecs are not supported, skip them */
> +			if (!this_len)
> +				continue;
> +			this_len = min(this_len, left);
>  
>  			ret = pipe_buf_confirm(pipe, buf);
>  			if (unlikely(ret)) {
> @@ -680,6 +682,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
>  			array[n].bv_len = this_len;
>  			array[n].bv_offset = buf->offset;
>  			left -= this_len;
> +			n++;
>  		}
>  
>  		iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
> -- 
> 2.24.0
> 

Reviewed-by: Ming Lei <[email protected]>

-- 
Ming


  reply	other threads:[~2021-01-11  2:50 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-09 16:02 [PATCH v3 0/7] no-copy bvec Pavel Begunkov
2021-01-09 16:02 ` [PATCH v3 1/7] splice: don't generate zero-len segement bvecs Pavel Begunkov
2021-01-11  2:48   ` Ming Lei [this message]
2021-01-09 16:02 ` [PATCH v3 2/7] bvec/iter: disallow zero-length segment bvecs Pavel Begunkov
2021-01-11  2:49   ` Ming Lei
2021-01-09 16:02 ` [PATCH v3 3/7] block/psi: remove PSI annotations from direct IO Pavel Begunkov
2021-01-11  2:52   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 4/7] target/file: allocate the bvec array as part of struct target_core_file_cmd Pavel Begunkov
2021-01-11  2:53   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 5/7] iov_iter: optimise bvec iov_iter_advance() Pavel Begunkov
2021-01-11  2:55   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 6/7] bio: add a helper calculating nr segments to alloc Pavel Begunkov
2021-01-11  2:57   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 7/7] bio: don't copy bvec for direct IO Pavel Begunkov
2021-01-11  3:00   ` Ming Lei
2021-01-25 15:58 ` [PATCH v3 0/7] no-copy bvec Jens Axboe

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