From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Andreas Grünbacher reports that on the two filesystems that support
iomap directio, it's possible for splice() to return -EAGAIN (instead of
a short splice) if the pipe being written to has less space available in
its pipe buffers than the length supplied by the calling process.
Months ago we fixed splice_direct_to_actor to clamp the length of the
read request to the size of the splice pipe. Do the same to do_splice.
Fixes: 17614445576b6 ("splice: don't read more than available pipe space")
Reported-by: Andreas Grünbacher <andreas.gruenbacher@xxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/splice.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/fs/splice.c b/fs/splice.c
index 98412721f056..7865a3bb6d88 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1101,6 +1101,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
struct pipe_inode_info *ipipe;
struct pipe_inode_info *opipe;
loff_t offset;
+ unsigned int pipe_pages;
long ret;
ipipe = get_pipe_info(in);
@@ -1123,6 +1124,10 @@ static long do_splice(struct file *in, loff_t __user *off_in,
if ((in->f_flags | out->f_flags) & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;
+ /* Don't try to read more the pipe has space for. */
+ pipe_pages = opipe->buffers - opipe->nrbufs;
+ len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
+
return splice_pipe_to_pipe(ipipe, opipe, len, flags);
}
@@ -1180,8 +1185,13 @@ static long do_splice(struct file *in, loff_t __user *off_in,
pipe_lock(opipe);
ret = wait_for_space(opipe, flags);
- if (!ret)
+ if (!ret) {
+ /* Don't try to read more the pipe has space for. */
+ pipe_pages = opipe->buffers - opipe->nrbufs;
+ len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
+
ret = do_splice_to(in, &offset, opipe, len, flags);
+ }
pipe_unlock(opipe);
if (ret > 0)
wakeup_pipe_readers(opipe);
