linux/fs/cachefiles
J. Bruce Fields b21996e36c locks: break delegations on unlink
We need to break delegations on any operation that changes the set of
links pointing to an inode.  Start with unlink.

Such operations also hold the i_mutex on a parent directory.  Breaking a
delegation may require waiting for a timeout (by default 90 seconds) in
the case of a unresponsive NFS client.  To avoid blocking all directory
operations, we therefore drop locks before waiting for the delegation.
The logic then looks like:

	acquire locks
	...
	test for delegation; if found:
		take reference on inode
		release locks
		wait for delegation break
		drop reference on inode
		retry

It is possible this could never terminate.  (Even if we take precautions
to prevent another delegation being acquired on the same inode, we could
get a different inode on each retry.)  But this seems very unlikely.

The initial test for a delegation happens after the lock on the target
inode is acquired, but the directory inode may have been acquired
further up the call stack.  We therefore add a "struct inode **"
argument to any intervening functions, which we use to pass the inode
back up to the caller in the case it needs a delegation synchronously
broken.

Cc: David Howells <dhowells@redhat.com>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Dustin Kirkland <dustin.kirkland@gazzang.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-11-09 00:16:42 -05:00
..
bind.c kill useless checks for sb->s_op == NULL 2011-07-20 01:44:21 -04:00
daemon.c llseek: automatically add .llseek fop 2010-10-15 15:53:27 +02:00
interface.c CacheFiles: Implement interface to check cache consistency 2013-09-06 09:17:30 +01:00
internal.h CacheFiles: Implement interface to check cache consistency 2013-09-06 09:17:30 +01:00
Kconfig CacheFiles: A cache that backs onto a mounted filesystem 2009-04-03 16:42:41 +01:00
key.c CacheFiles: Downgrade the requirements passed to the allocator 2012-12-20 21:58:25 +00:00
main.c CacheFiles: A cache that backs onto a mounted filesystem 2009-04-03 16:42:41 +01:00
Makefile CacheFiles: A cache that backs onto a mounted filesystem 2009-04-03 16:42:41 +01:00
namei.c locks: break delegations on unlink 2013-11-09 00:16:42 -05:00
proc.c CacheFiles: A cache that backs onto a mounted filesystem 2009-04-03 16:42:41 +01:00
rdwr.c mm: remove lru parameter from __pagevec_lru_add and remove parts of pagevec API 2013-07-03 16:07:31 -07:00
security.c CacheFiles: Fix error handling in cachefiles_determine_cache_security() 2010-05-12 18:23:58 -07:00
xattr.c CacheFiles: Fix memory leak in cachefiles_check_auxdata error paths 2013-09-20 15:15:42 -07:00