From 262b2fa99cbe02a715ce23981c2c30685ccf3a93 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 5 Feb 2025 19:17:47 +0100 Subject: [PATCH 1/2] pipe: introduce struct file_operations pipeanon_fops So that fifos and anonymous pipes could have different f_op methods. Preparation to simplify the next patch. Signed-off-by: Oleg Nesterov Link: https://lore.kernel.org/r/20250205181747.GB13817@redhat.com Tested-by: K Prateek Nayak Signed-off-by: Christian Brauner --- fs/pipe.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 94b59045ab44..2eacfde61e74 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -878,6 +878,8 @@ static const struct dentry_operations pipefs_dentry_operations = { .d_dname = pipefs_dname, }; +static const struct file_operations pipeanon_fops; + static struct inode * get_pipe_inode(void) { struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb); @@ -895,7 +897,7 @@ static struct inode * get_pipe_inode(void) inode->i_pipe = pipe; pipe->files = 2; pipe->readers = pipe->writers = 1; - inode->i_fop = &pipefifo_fops; + inode->i_fop = &pipeanon_fops; /* * Mark the inode dirty from the very beginning, @@ -938,7 +940,7 @@ int create_pipe_files(struct file **res, int flags) f = alloc_file_pseudo(inode, pipe_mnt, "", O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)), - &pipefifo_fops); + &pipeanon_fops); if (IS_ERR(f)) { free_pipe_info(inode->i_pipe); iput(inode); @@ -949,7 +951,7 @@ int create_pipe_files(struct file **res, int flags) f->f_pipe = 0; res[0] = alloc_file_clone(f, O_RDONLY | (flags & O_NONBLOCK), - &pipefifo_fops); + &pipeanon_fops); if (IS_ERR(res[0])) { put_pipe_info(inode, inode->i_pipe); fput(f); @@ -1107,8 +1109,8 @@ static void wake_up_partner(struct pipe_inode_info *pipe) static int fifo_open(struct inode *inode, struct file *filp) { + bool is_pipe = inode->i_fop == &pipeanon_fops; struct pipe_inode_info *pipe; - bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC; int ret; filp->f_pipe = 0; @@ -1241,6 +1243,17 @@ const struct file_operations pipefifo_fops = { .splice_write = iter_file_splice_write, }; +static const struct file_operations pipeanon_fops = { + .open = fifo_open, + .read_iter = pipe_read, + .write_iter = pipe_write, + .poll = pipe_poll, + .unlocked_ioctl = pipe_ioctl, + .release = pipe_release, + .fasync = pipe_fasync, + .splice_write = iter_file_splice_write, +}; + /* * Currently we rely on the pipe array holding a power-of-2 number * of pages. Returns 0 on error. @@ -1388,7 +1401,9 @@ struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice) { struct pipe_inode_info *pipe = file->private_data; - if (file->f_op != &pipefifo_fops || !pipe) + if (!pipe) + return NULL; + if (file->f_op != &pipefifo_fops && file->f_op != &pipeanon_fops) return NULL; if (for_splice && pipe_has_watch_queue(pipe)) return NULL; From f017b0a4951fac8f150232661b2cc0b67e0c57f0 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 5 Feb 2025 19:18:12 +0100 Subject: [PATCH 2/2] pipe: don't update {a,c,m}time for anonymous pipes 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 #include #include #include #include #include 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 Link: https://lore.kernel.org/r/20250205181812.GC13817@redhat.com Tested-by: K Prateek Nayak Signed-off-by: Christian Brauner --- fs/pipe.c | 41 +++++++++++++++++++++++++++++------------ 1 file changed, 29 insertions(+), 12 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 2eacfde61e74..2ae75adfba64 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -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 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) 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 @@ static int fifo_open(struct inode *inode, struct file *filp) 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,