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Subject[PATCH 1/3] 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>
---

fs/fscache/cookie.c | 7 +++++--
fs/fscache/page.c | 42 ++++++++++++++++++++++++++++++-----------
include/linux/fscache-cache.h | 19 +++++++++++++++++--
3 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index b2a86e3..d851aa5 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -568,6 +568,7 @@ int __fscache_check_consistency(struct fscache_cookie *cookie)
{
struct fscache_operation *op;
struct fscache_object *object;
+ bool wake_cookie = false;
int ret;

_enter("%p,", cookie);
@@ -600,7 +601,7 @@ int __fscache_check_consistency(struct fscache_cookie *cookie)

op->debug_id = atomic_inc_return(&fscache_op_debug_id);

- atomic_inc(&cookie->n_active);
+ __fscache_use_cookie(cookie);
if (fscache_submit_op(object, op) < 0)
goto submit_failed;

@@ -622,9 +623,11 @@ int __fscache_check_consistency(struct fscache_cookie *cookie)
return ret;

submit_failed:
- atomic_dec(&cookie->n_active);
+ wake_cookie = __fscache_unuse_cookie(cookie);
inconsistent:
spin_unlock(&cookie->lock);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
kfree(op);
_leave(" = -ESTALE");
return -ESTALE;
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 73899c1..0fe42a6 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -163,12 +163,10 @@ static void fscache_attr_changed_op(struct fscache_operation *op)

fscache_stat(&fscache_n_attr_changed_calls);

- if (fscache_object_is_active(object) &&
- fscache_use_cookie(object)) {
+ if (fscache_object_is_active(object)) {
fscache_stat(&fscache_n_cop_attr_changed);
ret = object->cache->ops->attr_changed(object);
fscache_stat_d(&fscache_n_cop_attr_changed);
- fscache_unuse_cookie(object);
if (ret < 0)
fscache_abort_object(object);
}
@@ -184,6 +182,7 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
{
struct fscache_operation *op;
struct fscache_object *object;
+ bool wake_cookie;

_enter("%p", cookie);

@@ -199,7 +198,9 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
}

fscache_operation_init(op, fscache_attr_changed_op, NULL);
- op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
+ op->flags = FSCACHE_OP_ASYNC |
+ (1 << FSCACHE_OP_EXCLUSIVE) |
+ (1 << FSCACHE_OP_UNUSE_COOKIE);

spin_lock(&cookie->lock);

@@ -208,6 +209,7 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);

+ __fscache_use_cookie(cookie);
if (fscache_submit_exclusive_op(object, op) < 0)
goto nobufs;
spin_unlock(&cookie->lock);
@@ -217,8 +219,11 @@ int __fscache_attr_changed(struct fscache_cookie *cookie)
return 0;

nobufs:
+ wake_cookie = __fscache_unuse_cookie(cookie);
spin_unlock(&cookie->lock);
kfree(op);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
fscache_stat(&fscache_n_attr_changed_nobufs);
_leave(" = %d", -ENOBUFS);
return -ENOBUFS;
@@ -263,7 +268,6 @@ static struct fscache_retrieval *fscache_alloc_retrieval(
}

fscache_operation_init(&op->op, NULL, fscache_release_retrieval_op);
- atomic_inc(&cookie->n_active);
op->op.flags = FSCACHE_OP_MYTHREAD |
(1UL << FSCACHE_OP_WAITING) |
(1UL << FSCACHE_OP_UNUSE_COOKIE);
@@ -384,6 +388,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
{
struct fscache_retrieval *op;
struct fscache_object *object;
+ bool wake_cookie = false;
int ret;

_enter("%p,%p,,,", cookie, page);
@@ -421,6 +426,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,

ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));

+ __fscache_use_cookie(cookie);
atomic_inc(&object->n_reads);
__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);

@@ -475,9 +481,11 @@ error:

nobufs_unlock_dec:
atomic_dec(&object->n_reads);
+ wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
spin_unlock(&cookie->lock);
- atomic_dec(&cookie->n_active);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
kfree(op);
nobufs:
fscache_stat(&fscache_n_retrievals_nobufs);
@@ -514,6 +522,7 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
{
struct fscache_retrieval *op;
struct fscache_object *object;
+ bool wake_cookie = false;
int ret;

_enter("%p,,%d,,,", cookie, *nr_pages);
@@ -547,6 +556,7 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);

+ __fscache_use_cookie(cookie);
atomic_inc(&object->n_reads);
__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);

@@ -601,10 +611,12 @@ error:

nobufs_unlock_dec:
atomic_dec(&object->n_reads);
+ wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
spin_unlock(&cookie->lock);
- atomic_dec(&cookie->n_active);
kfree(op);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
nobufs:
fscache_stat(&fscache_n_retrievals_nobufs);
_leave(" = -ENOBUFS");
@@ -626,6 +638,7 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
{
struct fscache_retrieval *op;
struct fscache_object *object;
+ bool wake_cookie = false;
int ret;

_enter("%p,%p,,,", cookie, page);
@@ -658,8 +671,9 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);

+ __fscache_use_cookie(cookie);
if (fscache_submit_op(object, &op->op) < 0)
- goto nobufs_unlock;
+ goto nobufs_unlock_dec;
spin_unlock(&cookie->lock);

fscache_stat(&fscache_n_alloc_ops);
@@ -689,10 +703,13 @@ error:
_leave(" = %d", ret);
return ret;

+nobufs_unlock_dec:
+ wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
spin_unlock(&cookie->lock);
- atomic_dec(&cookie->n_active);
kfree(op);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
nobufs:
fscache_stat(&fscache_n_allocs_nobufs);
_leave(" = -ENOBUFS");
@@ -889,6 +906,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
{
struct fscache_storage *op;
struct fscache_object *object;
+ bool wake_cookie = false;
int ret;

_enter("%p,%x,", cookie, (u32) page->flags);
@@ -957,7 +975,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
op->op.debug_id = atomic_inc_return(&fscache_op_debug_id);
op->store_limit = object->store_limit;

- atomic_inc(&cookie->n_active);
+ __fscache_use_cookie(cookie);
if (fscache_submit_op(object, &op->op) < 0)
goto submit_failed;

@@ -984,10 +1002,10 @@ already_pending:
return 0;

submit_failed:
- atomic_dec(&cookie->n_active);
spin_lock(&cookie->stores_lock);
radix_tree_delete(&cookie->stores, page->index);
spin_unlock(&cookie->stores_lock);
+ wake_cookie = __fscache_unuse_cookie(cookie);
page_cache_release(page);
ret = -ENOBUFS;
goto nobufs;
@@ -999,6 +1017,8 @@ nobufs:
spin_unlock(&cookie->lock);
radix_tree_preload_end();
kfree(op);
+ if (wake_cookie)
+ __fscache_wake_unused_cookie(cookie);
fscache_stat(&fscache_n_stores_nobufs);
_leave(" = -ENOBUFS");
return -ENOBUFS;
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 7823e9e..96a2b66 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);
}

/*


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