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pipe: take allocation and freeing of pipe_inode_info out of ->i_mutex

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* 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>
This commit is contained in:
Al Viro 2013-03-21 02:21:19 -04:00
parent 18c03cfd40
commit ba5bb14733
2 changed files with 53 additions and 21 deletions
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72
fs/pipe.c
View File

@ -718,23 +718,30 @@ pipe_poll(struct file *filp, poll_table *wait)
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 @@ static struct inode * get_pipe_inode(void)
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 @@ static int fifo_open(struct inode *inode, struct file *filp)
{
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 @@ static int fifo_open(struct inode *inode, struct file *filp)
}
/* Ok! */
mutex_unlock(&inode->i_mutex);
pipe_unlock(pipe);
return 0;
err_rd:
@ -1096,11 +1122,15 @@ err_wr:
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;
}

2
include/linux/pipe_fs_i.h
View File

@ -34,6 +34,7 @@ struct pipe_buffer {
* @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 @@ struct pipe_inode_info {
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;