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FS-Cache: Add use/unuse/wake cookie wrappers

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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 <dhowells@redhat.com>
This commit is contained in:
David Howells
2013-09-21 00:09:31 +01:00
parent 2457aaf73a
commit 8fb883f3e3
3 changed files with 53 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
include/linux/fscache-cache.h
View File

@@ -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);
}
/*