Move FASYNC bit handling to f_op->fasync()

[firefly-linux-kernel-4.4.55.git] / Documentation / filesystems / Locking

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index ec6a9392a1738317cdd8042fcd2f418865072396..4e78ce6778435aacf321de21baffe4095739f2e9 100644 (file)
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -437,8 +437,11 @@ grab BKL for cases when we close a file that had been opened r/w, but that
 can and should be done using the internal locking with smaller critical areas).
 Current worst offender is ext2_get_block()...
 
-->fasync() is a mess. This area needs a big cleanup and that will probably
-affect locking.
+->fasync() is called without BKL protection, and is responsible for
+maintaining the FASYNC bit in filp->f_flags.  Most instances call
+fasync_helper(), which does that maintenance, so it's not normally
+something one needs to worry about.  Return values > 0 will be mapped to
+zero in the VFS layer.
 
 ->readdir() and ->ioctl() on directories must be changed. Ideally we would
 move ->readdir() to inode_operations and use a separate method for directory