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authorJens Axboe <axboe@kernel.dk>2023-04-24 16:32:55 -0600
committerJens Axboe <axboe@kernel.dk>2023-04-25 14:08:55 -0600
commit0f99fc513ddd28de155c58547824a9fd63daacea (patch)
tree402b7ee95f3e94fc5d0e3b7d191b10e68899cd15
parent457391b0380335d5e9a5babdec90ac53928b23b4 (diff)
splice: clear FMODE_NOWAIT on file if splice/vmsplice is used
In preparation for pipes setting FMODE_NOWAIT on pipes to indicate that RWF_NOWAIT/IOCB_NOWAIT is fully supported, have splice and vmsplice clear that file flag. Splice holds the pipe lock around IO and cannot easily be refactored to avoid that, as splice and pipes are inherently tied together. By clearing FMODE_NOWAIT if splice is being used on a pipe, other users of the pipe will know that the pipe is no longer safe for RWF_NOWAIT and friends. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/splice.c34
1 files changed, 30 insertions, 4 deletions
diff --git a/fs/splice.c b/fs/splice.c
index 2c3dec2b6dfa..7aa90cfe91ba 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -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
* addition of remove_mapping(). If success is returned, the caller may
@@ -1211,10 +1227,16 @@ 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)))
@@ -1311,6 +1333,8 @@ 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);
@@ -1339,6 +1363,8 @@ 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)