[PATCH v2 1/7] splice: don't generate zero-len segement bvecs

[Pavel Begunkov]

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 <asml.sile...@gmail.com>
---
 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