linux/fs/9p
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 fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
Makefile fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
acl.c 9p: switch v9fs_set_create_acl() to inode+fid, do it before d_instantiate() 2013-02-26 02:46:07 -05:00
acl.h 9p: switch v9fs_set_create_acl() to inode+fid, do it before d_instantiate() 2013-02-26 02:46:07 -05:00
cache.c FS-Cache: Provide the ability to enable/disable cookies 2013-09-27 18:40:25 +01:00
cache.h fs/9p: When doing inode lookup compare qid details and inode mode bits. 2011-07-23 09:32:48 -05:00
fid.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-03-03 13:23:03 -08:00
fid.h 9p: v9fs_fid_add() can't fail now 2013-02-28 01:18:14 -05:00
v9fs.c 9p: don't forget to destroy inode cache if fscache registration fails 2013-09-17 22:31:01 -04:00
v9fs.h 9p: Modify struct v9fs_session_info to use a kuids and kgids 2013-02-12 03:19:33 -08:00
v9fs_vfs.h 9p: propagate umode_t 2012-01-03 22:55:01 -05:00
vfs_addr.c mm: change invalidatepage prototype to accept length 2013-05-21 23:17:23 -04:00
vfs_dentry.c v9fs: get rid of v9fs_dentry 2013-02-28 01:13:19 -05:00
vfs_dir.c [readdir] convert 9p 2013-06-29 12:56:45 +04:00
vfs_file.c fs/9p: avoid accessing utsname after namespace has been torn down 2013-08-26 10:28:46 -05:00
vfs_inode.c fs: 9p: use strlcpy instead of strncpy 2013-07-30 10:42:56 -05:00
vfs_inode_dotl.c atomic_open: take care of EEXIST in no-open case with O_CREAT|O_EXCL in fs/namei.c 2013-09-17 17:08:50 -04:00
vfs_super.c fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
xattr.c fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
xattr.h fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
xattr_security.c fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
xattr_trusted.c fs/9p: xattr: add trusted and security namespaces 2013-07-07 22:02:18 -05:00
xattr_user.c fs/9p: Add support user. xattr 2010-08-02 14:28:35 -05:00