From 8fb883f3e30065529e4f35d4b4f355193dcdb7a2 Mon Sep 17 00:00:00 2001 From: David Howells Date: Sat, 21 Sep 2013 00:09:31 +0100 Subject: FS-Cache: Add use/unuse/wake cookie wrappers Add wrapper functions for dealing with cookie->n_active: (*) __fscache_use_cookie() to increment it. (*) __fscache_unuse_cookie() to decrement and test against zero. (*) __fscache_wake_unused_cookie() to wake up anyone waiting for it to reach zero. The second and third are split so that the third can be done after cookie->lock has been released in case the waiter wakes up whilst we're still holding it and tries to get it. We will need to wake-on-zero once the cookie disablement patch is applied because it will then be possible to see n_active become zero without the cookie being relinquished. Also move the cookie usement out of fscache_attr_changed_op() and into fscache_attr_changed() and the operation struct so that cookie disablement will be able to track it. Whilst we're at it, only increment n_active if we're about to do fscache_submit_op() so that we don't have to deal with undoing it if anything earlier fails. Possibly this should be moved into fscache_submit_op() which could look at FSCACHE_OP_UNUSE_COOKIE. Signed-off-by: David Howells --- include/linux/fscache-cache.h | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) (limited to 'include/linux/fscache-cache.h') diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index 7823e9ef995e..96a2b66f5968 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -511,6 +511,11 @@ static inline void fscache_end_io(struct fscache_retrieval *op, op->end_io_func(page, op->context, error); } +static inline void __fscache_use_cookie(struct fscache_cookie *cookie) +{ + atomic_inc(&cookie->n_active); +} + /** * fscache_use_cookie - Request usage of cookie attached to an object * @object: Object description @@ -524,6 +529,16 @@ static inline bool fscache_use_cookie(struct fscache_object *object) return atomic_inc_not_zero(&cookie->n_active) != 0; } +static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie) +{ + return atomic_dec_and_test(&cookie->n_active); +} + +static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie) +{ + wake_up_atomic_t(&cookie->n_active); +} + /** * fscache_unuse_cookie - Cease usage of cookie attached to an object * @object: Object description @@ -534,8 +549,8 @@ static inline bool fscache_use_cookie(struct fscache_object *object) static inline void fscache_unuse_cookie(struct fscache_object *object) { struct fscache_cookie *cookie = object->cookie; - if (atomic_dec_and_test(&cookie->n_active)) - wake_up_atomic_t(&cookie->n_active); + if (__fscache_unuse_cookie(cookie)) + __fscache_wake_unused_cookie(cookie); } /* -- cgit From 94d30ae90a00cafe686c1057be57f4885f963abf Mon Sep 17 00:00:00 2001 From: David Howells Date: Sat, 21 Sep 2013 00:09:31 +0100 Subject: 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 object_list */ struct hlist_node cookie_link; /* link in cookie->backing_objects */ -- cgit