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pipe: don't update {a,c,m}time for anonymous pipes

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These numbers are visible in fstat() but hopefully nobody uses this
information and file_accessed/file_update_time are not that cheap.
Stupid test-case:

	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <assert.h>
	#include <sys/ioctl.h>
	#include <sys/time.h>

	static char buf[17 * 4096];
	static struct timeval TW, TR;

	int wr(int fd, int size)
	{
		int c, r;
		struct timeval t0, t1;

		gettimeofday(&t0, NULL);
		for (c = 0; (r = write(fd, buf, size)) > 0; c += r);
		gettimeofday(&t1, NULL);
		timeradd(&TW, &t1, &TW);
		timersub(&TW, &t0, &TW);

		return c;
	}

	int rd(int fd, int size)
	{
		int c, r;
		struct timeval t0, t1;

		gettimeofday(&t0, NULL);
		for (c = 0; (r = read(fd, buf, size)) > 0; c += r);
		gettimeofday(&t1, NULL);
		timeradd(&TR, &t1, &TR);
		timersub(&TR, &t0, &TR);

		return c;
	}

	int main(int argc, const char *argv[])
	{
		int fd[2], nb = 1, loop, size;

		assert(argc == 3);
		loop = atoi(argv[1]);
		size = atoi(argv[2]);

		assert(pipe(fd) == 0);
		assert(ioctl(fd[0], FIONBIO, &nb) == 0);
		assert(ioctl(fd[1], FIONBIO, &nb) == 0);

		assert(size <= sizeof(buf));
		while (loop--)
			assert(wr(fd[1], size) == rd(fd[0], size));

		struct timeval tt;
		timeradd(&TW, &TR, &tt);
		printf("TW = %lu.%03lu TR = %lu.%03lu TT = %lu.%03lu\n",
			TW.tv_sec, TW.tv_usec/1000,
			TR.tv_sec, TR.tv_usec/1000,
			tt.tv_sec, tt.tv_usec/1000);

		return 0;
	}

Before:
	# for i in 1 2 3; do /host/tmp/test 10000 100; done
	TW = 8.047 TR = 5.845 TT = 13.893
	TW = 8.091 TR = 5.872 TT = 13.963
	TW = 8.083 TR = 5.885 TT = 13.969
After:
	# for i in 1 2 3; do /host/tmp/test 10000 100; done
	TW = 4.752 TR = 4.664 TT = 9.416
	TW = 4.684 TR = 4.608 TT = 9.293
	TW = 4.736 TR = 4.652 TT = 9.388

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250205181812.GC13817@redhat.com
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Oleg Nesterov 2025-02-05 19:18:12 +01:00 • committed by Christian Brauner
commit f017b0a495
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
1 changed files with 29 additions and 12 deletions
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41
fs/pipe.c
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@ -248,7 +248,7 @@ static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe,
}
static ssize_t
pipe_read(struct kiocb *iocb, struct iov_iter *to)
anon_pipe_read(struct kiocb *iocb, struct iov_iter *to)
{
size_t total_len = iov_iter_count(to);
struct file *filp = iocb->ki_filp;
@ -404,8 +404,15 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (wake_next_reader)
wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
return ret;
}
static ssize_t
fifo_pipe_read(struct kiocb *iocb, struct iov_iter *to)
{
int ret = anon_pipe_read(iocb, to);
if (ret > 0)
file_accessed(filp);
file_accessed(iocb->ki_filp);
return ret;
}
@ -426,7 +433,7 @@ static inline bool pipe_writable(const struct pipe_inode_info *pipe)
}
static ssize_t
pipe_write(struct kiocb *iocb, struct iov_iter *from)
anon_pipe_write(struct kiocb *iocb, struct iov_iter *from)
{
struct file *filp = iocb->ki_filp;
struct pipe_inode_info *pipe = filp->private_data;
@ -604,11 +611,21 @@ out:
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
if (wake_next_writer)
wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);
if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
int err = file_update_time(filp);
if (err)
ret = err;
sb_end_write(file_inode(filp)->i_sb);
return ret;
}
static ssize_t
fifo_pipe_write(struct kiocb *iocb, struct iov_iter *from)
{
int ret = anon_pipe_write(iocb, from);
if (ret > 0) {
struct file *filp = iocb->ki_filp;
if (sb_start_write_trylock(file_inode(filp)->i_sb)) {
int err = file_update_time(filp);
if (err)
ret = err;
sb_end_write(file_inode(filp)->i_sb);
}
}
return ret;
}
@ -1234,8 +1251,8 @@ err:
const struct file_operations pipefifo_fops = {
.open = fifo_open,
.read_iter = pipe_read,
.write_iter = pipe_write,
.read_iter = fifo_pipe_read,
.write_iter = fifo_pipe_write,
.poll = pipe_poll,
.unlocked_ioctl = pipe_ioctl,
.release = pipe_release,
@ -1245,8 +1262,8 @@ const struct file_operations pipefifo_fops = {
static const struct file_operations pipeanon_fops = {
.open = fifo_open,
.read_iter = pipe_read,
.write_iter = pipe_write,
.read_iter = anon_pipe_read,
.write_iter = anon_pipe_write,
.poll = pipe_poll,
.unlocked_ioctl = pipe_ioctl,
.release = pipe_release,