linux/fs/ceph
David Howells 94d30ae90a FS-Cache: Provide the ability to enable/disable cookies
Provide the ability to enable and disable fscache cookies.  A disabled cookie
will reject or ignore further requests to:

	Acquire a child cookie
	Invalidate and update backing objects
	Check the consistency of a backing object
	Allocate storage for backing page
	Read backing pages
	Write to backing pages

but still allows:

	Checks/waits on the completion of already in-progress objects
	Uncaching of pages
	Relinquishment of cookies

Two new operations are provided:

 (1) Disable a cookie:

	void fscache_disable_cookie(struct fscache_cookie *cookie,
				    bool invalidate);

     If the cookie is not already disabled, this locks the cookie against other
     dis/enablement ops, marks the cookie as being disabled, discards or
     invalidates any backing objects and waits for cessation of activity on any
     associated object.

     This is a wrapper around a chunk split out of fscache_relinquish_cookie(),
     but it reinitialises the cookie such that it can be reenabled.

     All possible failures are handled internally.  The caller should consider
     calling fscache_uncache_all_inode_pages() afterwards to make sure all page
     markings are cleared up.

 (2) Enable a cookie:

	void fscache_enable_cookie(struct fscache_cookie *cookie,
				   bool (*can_enable)(void *data),
				   void *data)

     If the cookie is not already enabled, this locks the cookie against other
     dis/enablement ops, invokes can_enable() and, if the cookie is not an
     index cookie, will begin the procedure of acquiring backing objects.

     The optional can_enable() function is passed the data argument and returns
     a ruling as to whether or not enablement should actually be permitted to
     begin.

     All possible failures are handled internally.  The cookie will only be
     marked as enabled if provisional backing objects are allocated.

A later patch will introduce these to NFS.  Cookie enablement during nfs_open()
is then contingent on i_writecount <= 0.  can_enable() checks for a race
between open(O_RDONLY) and open(O_WRONLY/O_RDWR).  This simplifies NFS's cookie
handling and allows us to get rid of open(O_RDONLY) accidentally introducing
caching to an inode that's open for writing already.

One operation has its API modified:

 (3) Acquire a cookie.

	struct fscache_cookie *fscache_acquire_cookie(
		struct fscache_cookie *parent,
		const struct fscache_cookie_def *def,
		void *netfs_data,
		bool enable);

     This now has an additional argument that indicates whether the requested
     cookie should be enabled by default.  It doesn't need the can_enable()
     function because the caller must prevent multiple calls for the same netfs
     object and it doesn't need to take the enablement lock because no one else
     can get at the cookie before this returns.

Signed-off-by: David Howells <dhowells@redhat.com
2013-09-27 18:40:25 +01:00
..
Kconfig ceph: use fscache as a local presisent cache 2013-09-06 16:50:11 +00:00
Makefile ceph: use fscache as a local presisent cache 2013-09-06 16:50:11 +00:00
addr.c ceph: page still marked private_2 2013-09-06 16:50:12 +00:00
cache.c FS-Cache: Provide the ability to enable/disable cookies 2013-09-27 18:40:25 +01:00
cache.h ceph: trivial buildbot warnings fix 2013-09-06 16:50:12 +00:00
caps.c ceph: use d_invalidate() to invalidate aliases 2013-09-06 12:55:29 -07:00
ceph_frag.c ceph: factor out libceph from Ceph file system 2010-10-20 15:37:28 -07:00
debugfs.c libceph: delay debugfs initialization until we learn global_id 2012-08-20 10:03:15 -07:00
dir.c Merge remote-tracking branch 'linus/master' into testing 2013-08-15 11:11:45 -07:00
export.c fs: encode_fh: return FILEID_INVALID if invalid fid_type 2013-02-26 02:46:10 -05:00
file.c ceph: use fscache as a local presisent cache 2013-09-06 16:50:11 +00:00
inode.c ceph: remove ceph_lookup_inode() 2013-09-06 12:55:09 -07:00
ioctl.c ceph: Add check returned value on func ceph_calc_ceph_pg. 2013-08-09 17:55:21 -07:00
ioctl.h ceph: fully initialize new layout 2012-05-16 14:28:27 -05:00
locks.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2013-07-09 12:39:10 -07:00
mds_client.c ceph: remove ceph_lookup_inode() 2013-09-06 12:55:09 -07:00
mds_client.h Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2013-02-28 17:43:09 -08:00
mdsmap.c ceph: tidy ceph_mdsmap_decode() a little 2013-07-01 09:52:02 -07:00
snap.c ceph: use ceph_create_snap_context() 2013-05-01 21:20:09 -07:00
strings.c libceph: update ceph_mds_state_name() and ceph_mds_op_name() 2013-02-18 12:20:34 -06:00
super.c ceph: use fscache as a local presisent cache 2013-09-06 16:50:11 +00:00
super.h ceph: remove ceph_lookup_inode() 2013-09-06 12:55:09 -07:00
xattr.c ceph: fix sleeping function called from invalid context. 2013-07-03 15:32:51 -07:00