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pipe-nonblock-2023-05-06 

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Merge tag 'pipe-nonblock-2023-05-06' of git://git.kernel.dk/linux

Pull nonblocking pipe io_uring support from Jens Axboe:
 "Here's the revised edition of the FMODE_NOWAIT support for pipes, in
  which we just flag it as such supporting FMODE_NOWAIT unconditionally,
  but clear it if we ever end up using splice/vmsplice on the pipe.

  The pipe read/write side is perfectly fine for nonblocking IO, however
  splice and vmsplice can potentially wait for IO with the pipe lock
  held"

* tag 'pipe-nonblock-2023-05-06' of git://git.kernel.dk/linux:
  pipe: set FMODE_NOWAIT on pipes
  splice: clear FMODE_NOWAIT on file if splice/vmsplice is used
This commit is contained in:
Linus Torvalds 2023-05-06 08:15:20 -07:00
parent 0021b532b2 afed6271f5
commit 7644c82319
2 changed files with 33 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/pipe.c
View File

@ -976,6 +976,9 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags)
audit_fd_pair(fdr, fdw);
fd[0] = fdr;
fd[1] = fdw;
/* pipe groks IOCB_NOWAIT */
files[0]->f_mode |= FMODE_NOWAIT;
files[1]->f_mode |= FMODE_NOWAIT;
return 0;
err_fdr:

34
fs/splice.c
View File

@ -38,6 +38,22 @@
#include "internal.h"
/*
* Splice doesn't support FMODE_NOWAIT. Since pipes may set this flag to
* indicate they support non-blocking reads or writes, we must clear it
* here if set to avoid blocking other users of this pipe if splice is
* being done on it.
*/
static noinline void noinline pipe_clear_nowait(struct file *file)
{
fmode_t fmode = READ_ONCE(file->f_mode);
do {
if (!(fmode & FMODE_NOWAIT))
break;
} while (!try_cmpxchg(&file->f_mode, &fmode, fmode & ~FMODE_NOWAIT));
}
/*
* Attempt to steal a page from a pipe buffer. This should perhaps go into
* a vm helper function, it's already simplified quite a bit by the
@ -1219,10 +1235,16 @@ static long __do_splice(struct file *in, loff_t __user *off_in,
ipipe = get_pipe_info(in, true);
opipe = get_pipe_info(out, true);
if (ipipe && off_in)
return -ESPIPE;
if (opipe && off_out)
return -ESPIPE;
if (ipipe) {
if (off_in)
return -ESPIPE;
pipe_clear_nowait(in);
}
if (opipe) {
if (off_out)
return -ESPIPE;
pipe_clear_nowait(out);
}
if (off_out) {
if (copy_from_user(&offset, off_out, sizeof(loff_t)))
@ -1319,6 +1341,8 @@ static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
if (!pipe)
return -EBADF;
pipe_clear_nowait(file);
if (sd.total_len) {
pipe_lock(pipe);
ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
@ -1347,6 +1371,8 @@ static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
if (!pipe)
return -EBADF;
pipe_clear_nowait(file);
pipe_lock(pipe);
ret = wait_for_space(pipe, flags);
if (!ret)