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From: Pavel Begunkov <[email protected]>
To: [email protected]
Cc: Jens Axboe <[email protected]>,
	Christoph Hellwig <[email protected]>,
	Matthew Wilcox <[email protected]>,
	Ming Lei <[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]
Subject: [PATCH v2 1/7] splice: don't generate zero-len segement bvecs
Date: Sat,  2 Jan 2021 15:17:33 +0000	[thread overview]
Message-ID: <ca14f80bf5156d83b38f543be2b9434a571474c9.1609461359.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>

iter_file_splice_write() may spawn bvec segments with zero-length. In
preparation for prohibiting them, filter out by hand at splice level.

Signed-off-by: Pavel Begunkov <[email protected]>
---
 fs/splice.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 866d5c2367b2..7299330c3270 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -644,7 +644,6 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		ret = splice_from_pipe_next(pipe, &sd);
 		if (ret <= 0)
 			break;
-
 		if (unlikely(nbufs < pipe->max_usage)) {
 			kfree(array);
 			nbufs = pipe->max_usage;
@@ -662,12 +661,13 @@ 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;
+			if (!this_len)
+				continue;
+			this_len = min(this_len, left);
 
 			ret = pipe_buf_confirm(pipe, buf);
 			if (unlikely(ret)) {
@@ -680,6 +680,7 @@ 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


  reply	other threads:[~2021-01-02 15:22 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-02 15:17 [PATCH v2 0/7] no-copy bvec Pavel Begunkov
2021-01-02 15:17 ` Pavel Begunkov [this message]
2021-01-04 16:17   ` [PATCH v2 1/7] splice: don't generate zero-len segement bvecs Christoph Hellwig
2021-01-04 16:54     ` Pavel Begunkov
2021-01-02 15:17 ` [PATCH v2 2/7] bvec/iter: disallow zero-length segment bvecs Pavel Begunkov
2021-01-04 16:18   ` Christoph Hellwig
2021-01-04 16:37   ` Matthew Wilcox
2021-01-04 17:23     ` Pavel Begunkov
2021-01-02 15:17 ` [PATCH v2 3/7] block/psi: remove PSI annotations from direct IO Pavel Begunkov
2021-01-04 16:45   ` Christoph Hellwig
2021-01-02 15:17 ` [PATCH v2 4/7] target/file: allocate the bvec array as part of struct target_core_file_cmd Pavel Begunkov
2021-01-02 15:17 ` [PATCH v2 5/7] iov_iter: optimise bvec iov_iter_advance() Pavel Begunkov
2021-01-02 15:17 ` [PATCH v2 6/7] bio: add a helper calculating nr segments to alloc Pavel Begunkov
2021-01-02 15:17 ` [PATCH v2 7/7] bio: don't copy bvec for direct IO Pavel Begunkov
2021-01-04 16:20   ` Christoph Hellwig

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