[0/2] pipe: change pipe_write() to never add a zero-sized buffer

Message

Oleg Nesterov Feb. 9, 2025, 3:07 p.m. UTC

Please review.

pipe_write() can insert the empty buffer and this looks very confusing
to me. Because it looks obviously unnecessary and complicates the code.

In fact this logic doesn't even look strictly correct. For example,
eat_empty_buffer() simply updates pipe->tail but (unlike pipe_read) it
doesn't wake the writers.

But is pipe_write() is the only possible source of buf->len == 0 ?
I am not 100% sure, fs/splice.c is very nontrivial, but it seems that
this code at least tries to not add a zero-sized buf into pipe->bufs.

Oleg.
---

 fs/pipe.c                 | 47 ++++++++++-------------------------------------
 fs/splice.c               | 14 ++++++--------
 include/linux/pipe_fs_i.h |  6 ++++++
 3 files changed, 22 insertions(+), 45 deletions(-)

Comments

Christian Brauner Feb. 10, 2025, 12:52 p.m. UTC | #1

On Sun, 09 Feb 2025 16:07:18 +0100, Oleg Nesterov wrote:
> Please review.
> 
> pipe_write() can insert the empty buffer and this looks very confusing
> to me. Because it looks obviously unnecessary and complicates the code.
> 
> In fact this logic doesn't even look strictly correct. For example,
> eat_empty_buffer() simply updates pipe->tail but (unlike pipe_read) it
> doesn't wake the writers.
> 
> [...]

Applied to the vfs-6.15.misc branch of the vfs/vfs.git tree.
Patches in the vfs-6.15.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.15.misc

[1/1] pipe: change pipe_write() to never add a zero-sized buffer
      https://git.kernel.org/vfs/vfs/c/af69e27b3c82