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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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2
include/linux/pipe_fs_i.h
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@ -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;