pipe: take allocation and freeing of pipe_inode_info out of ->i_mutex
* new field - pipe->files; number of struct file over that pipe (all
sharing the same inode, of course); protected by inode->i_lock.
* pipe_release() decrements pipe->files, clears inode->i_pipe when
if the counter has reached 0 (all under ->i_lock) and, in that case,
frees pipe after having done pipe_unlock()
* fifo_open() starts with grabbing ->i_lock, and either bumps pipe->files
if ->i_pipe was non-NULL or allocates a new pipe (dropping and regaining
->i_lock) and rechecks ->i_pipe; if it's still NULL, inserts new pipe
there, otherwise bumps ->i_pipe->files and frees the one we'd allocated.
At that point we know that ->i_pipe is non-NULL and won't go away, so
we can do pipe_lock() on it and proceed as we used to. If we end up
failing, decrement pipe->files and if it reaches 0 clear ->i_pipe and
free the sucker after pipe_unlock().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/pipe.c b/fs/pipe.c
index 357471d..abaa923 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -718,23 +718,30 @@
static int
pipe_release(struct inode *inode, struct file *file)
{
- struct pipe_inode_info *pipe;
+ struct pipe_inode_info *pipe = inode->i_pipe;
+ int kill = 0;
- mutex_lock(&inode->i_mutex);
- pipe = inode->i_pipe;
+ pipe_lock(pipe);
if (file->f_mode & FMODE_READ)
pipe->readers--;
if (file->f_mode & FMODE_WRITE)
pipe->writers--;
- if (!pipe->readers && !pipe->writers) {
- free_pipe_info(inode);
- } else {
+ if (pipe->readers || pipe->writers) {
wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}
- mutex_unlock(&inode->i_mutex);
+ spin_lock(&inode->i_lock);
+ if (!--pipe->files) {
+ inode->i_pipe = NULL;
+ kill = 1;
+ }
+ spin_unlock(&inode->i_lock);
+ pipe_unlock(pipe);
+
+ if (kill)
+ __free_pipe_info(pipe);
return 0;
}
@@ -827,8 +834,9 @@
pipe = alloc_pipe_info(inode);
if (!pipe)
goto fail_iput;
- inode->i_pipe = pipe;
+ inode->i_pipe = pipe;
+ pipe->files = 2;
pipe->readers = pipe->writers = 1;
inode->i_fop = &pipefifo_fops;
@@ -999,18 +1007,36 @@
{
struct pipe_inode_info *pipe;
bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
+ int kill = 0;
int ret;
- mutex_lock(&inode->i_mutex);
- pipe = inode->i_pipe;
- if (!pipe) {
- ret = -ENOMEM;
+ filp->f_version = 0;
+
+ spin_lock(&inode->i_lock);
+ if (inode->i_pipe) {
+ pipe = inode->i_pipe;
+ pipe->files++;
+ spin_unlock(&inode->i_lock);
+ } else {
+ spin_unlock(&inode->i_lock);
pipe = alloc_pipe_info(inode);
if (!pipe)
- goto err_nocleanup;
- inode->i_pipe = pipe;
+ return -ENOMEM;
+ pipe->files = 1;
+ spin_lock(&inode->i_lock);
+ if (unlikely(inode->i_pipe)) {
+ inode->i_pipe->files++;
+ spin_unlock(&inode->i_lock);
+ __free_pipe_info(pipe);
+ pipe = inode->i_pipe;
+ } else {
+ inode->i_pipe = pipe;
+ spin_unlock(&inode->i_lock);
+ }
}
- filp->f_version = 0;
+ /* OK, we have a pipe and it's pinned down */
+
+ pipe_lock(pipe);
/* We can only do regular read/write on fifos */
filp->f_mode &= (FMODE_READ | FMODE_WRITE);
@@ -1080,7 +1106,7 @@
}
/* Ok! */
- mutex_unlock(&inode->i_mutex);
+ pipe_unlock(pipe);
return 0;
err_rd:
@@ -1096,11 +1122,15 @@
goto err;
err:
- if (!pipe->readers && !pipe->writers)
- free_pipe_info(inode);
-
-err_nocleanup:
- mutex_unlock(&inode->i_mutex);
+ spin_lock(&inode->i_lock);
+ if (!--pipe->files) {
+ inode->i_pipe = NULL;
+ kill = 1;
+ }
+ spin_unlock(&inode->i_lock);
+ pipe_unlock(pipe);
+ if (kill)
+ __free_pipe_info(pipe);
return ret;
}
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index ad1a427..59778e1 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -34,6 +34,7 @@
* @tmp_page: cached released page
* @readers: number of current readers of this pipe
* @writers: number of current writers of this pipe
+ * @files: number of struct file refering this pipe (protected by ->i_lock)
* @waiting_writers: number of writers blocked waiting for room
* @r_counter: reader counter
* @w_counter: writer counter
@@ -47,6 +48,7 @@
unsigned int nrbufs, curbuf, buffers;
unsigned int readers;
unsigned int writers;
+ unsigned int files;
unsigned int waiting_writers;
unsigned int r_counter;
unsigned int w_counter;
