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Message-ID: <164021507345.640689.4073511598838843040.stgit@warthog.procyon.org.uk>
Date: Wed, 22 Dec 2021 23:17:53 +0000
From: David Howells <dhowells@...hat.com>
To: linux-cachefs@...hat.com
Cc: Jeff Layton <jlayton@...nel.org>, dhowells@...hat.com,
Trond Myklebust <trondmy@...merspace.com>,
Anna Schumaker <anna.schumaker@...app.com>,
Steve French <sfrench@...ba.org>,
Dominique Martinet <asmadeus@...ewreck.org>,
Jeff Layton <jlayton@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Omar Sandoval <osandov@...ndov.com>,
JeffleXu <jefflexu@...ux.alibaba.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
v9fs-developer@...ts.sourceforge.net,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 15/68] fscache: Provide and use cache methods to
lookup/create/free a volume
Add cache methods to lookup, create and remove a volume.
Looking up or creating the volume requires the cache pinning for access;
freeing the volume requires the volume pinning for access. The
->acquire_volume() method is used to ask the cache backend to lookup and,
if necessary, create a volume; the ->free_volume() method is used to free
the resources for a volume.
Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...nel.org>
cc: linux-cachefs@...hat.com
Link: https://lore.kernel.org/r/163819597821.215744.5225318658134989949.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906898645.143852.8537799955945956818.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967099771.1823006.1455197910571061835.stgit@warthog.procyon.org.uk/ # v3
---
fs/fscache/volume.c | 89 +++++++++++++++++++++++++++++++++++++++-
include/linux/fscache-cache.h | 7 +++
include/trace/events/fscache.h | 11 ++++-
3 files changed, 103 insertions(+), 4 deletions(-)
diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c
index 20497f0f10bb..e1a8e92a6adb 100644
--- a/fs/fscache/volume.c
+++ b/fs/fscache/volume.c
@@ -15,6 +15,8 @@ static struct hlist_bl_head fscache_volume_hash[1 << fscache_volume_hash_shift];
static atomic_t fscache_volume_debug_id;
static LIST_HEAD(fscache_volumes);
+static void fscache_create_volume_work(struct work_struct *work);
+
struct fscache_volume *fscache_get_volume(struct fscache_volume *volume,
enum fscache_volume_trace where)
{
@@ -213,7 +215,7 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key,
volume->cache = cache;
INIT_LIST_HEAD(&volume->proc_link);
- INIT_WORK(&volume->work, NULL /* PLACEHOLDER */);
+ INIT_WORK(&volume->work, fscache_create_volume_work);
refcount_set(&volume->ref, 1);
spin_lock_init(&volume->lock);
@@ -249,6 +251,58 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key,
return NULL;
}
+/*
+ * Create a volume's representation on disk. Have a volume ref and a cache
+ * access we have to release.
+ */
+static void fscache_create_volume_work(struct work_struct *work)
+{
+ const struct fscache_cache_ops *ops;
+ struct fscache_volume *volume =
+ container_of(work, struct fscache_volume, work);
+
+ fscache_see_volume(volume, fscache_volume_see_create_work);
+
+ ops = volume->cache->ops;
+ if (ops->acquire_volume)
+ ops->acquire_volume(volume);
+ fscache_end_cache_access(volume->cache,
+ fscache_access_acquire_volume_end);
+
+ clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
+ wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
+ fscache_put_volume(volume, fscache_volume_put_create_work);
+}
+
+/*
+ * Dispatch a worker thread to create a volume's representation on disk.
+ */
+void fscache_create_volume(struct fscache_volume *volume, bool wait)
+{
+ if (test_and_set_bit(FSCACHE_VOLUME_CREATING, &volume->flags))
+ goto maybe_wait;
+ if (volume->cache_priv)
+ goto no_wait; /* We raced */
+ if (!fscache_begin_cache_access(volume->cache,
+ fscache_access_acquire_volume))
+ goto no_wait;
+
+ fscache_get_volume(volume, fscache_volume_get_create_work);
+ if (!schedule_work(&volume->work))
+ fscache_put_volume(volume, fscache_volume_put_create_work);
+
+maybe_wait:
+ if (wait) {
+ fscache_see_volume(volume, fscache_volume_wait_create_work);
+ wait_on_bit(&volume->flags, FSCACHE_VOLUME_CREATING,
+ TASK_UNINTERRUPTIBLE);
+ }
+ return;
+no_wait:
+ clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
+ wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
+}
+
/*
* Acquire a volume representation cookie and link it to a (proposed) cache.
*/
@@ -269,7 +323,7 @@ struct fscache_volume *__fscache_acquire_volume(const char *volume_key,
return ERR_PTR(-EBUSY);
}
- // PLACEHOLDER: Create the volume if we have a cache available
+ fscache_create_volume(volume, false);
return volume;
}
EXPORT_SYMBOL(__fscache_acquire_volume);
@@ -316,7 +370,12 @@ static void fscache_free_volume(struct fscache_volume *volume)
struct fscache_cache *cache = volume->cache;
if (volume->cache_priv) {
- // PLACEHOLDER: Detach any attached cache
+ __fscache_begin_volume_access(volume, NULL,
+ fscache_access_relinquish_volume);
+ if (volume->cache_priv)
+ cache->ops->free_volume(volume);
+ fscache_end_volume_access(volume, NULL,
+ fscache_access_relinquish_volume_end);
}
down_write(&fscache_addremove_sem);
@@ -369,6 +428,30 @@ void __fscache_relinquish_volume(struct fscache_volume *volume,
}
EXPORT_SYMBOL(__fscache_relinquish_volume);
+/**
+ * fscache_withdraw_volume - Withdraw a volume from being cached
+ * @volume: Volume cookie
+ *
+ * Withdraw a cache volume from service, waiting for all accesses to complete
+ * before returning.
+ */
+void fscache_withdraw_volume(struct fscache_volume *volume)
+{
+ int n_accesses;
+
+ _debug("withdraw V=%x", volume->debug_id);
+
+ /* Allow wakeups on dec-to-0 */
+ n_accesses = atomic_dec_return(&volume->n_accesses);
+ trace_fscache_access_volume(volume->debug_id, 0,
+ refcount_read(&volume->ref),
+ n_accesses, fscache_access_cache_unpin);
+
+ wait_var_event(&volume->n_accesses,
+ atomic_read(&volume->n_accesses) == 0);
+}
+EXPORT_SYMBOL(fscache_withdraw_volume);
+
#ifdef CONFIG_PROC_FS
/*
* Generate a list of volumes in /proc/fs/fscache/volumes
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index f78add6e7823..a10b66ca3544 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -51,6 +51,12 @@ struct fscache_cache {
struct fscache_cache_ops {
/* name of cache provider */
const char *name;
+
+ /* Acquire a volume */
+ void (*acquire_volume)(struct fscache_volume *volume);
+
+ /* Free the cache's data attached to a volume */
+ void (*free_volume)(struct fscache_volume *volume);
};
extern struct workqueue_struct *fscache_wq;
@@ -65,6 +71,7 @@ extern int fscache_add_cache(struct fscache_cache *cache,
const struct fscache_cache_ops *ops,
void *cache_priv);
extern void fscache_withdraw_cache(struct fscache_cache *cache);
+extern void fscache_withdraw_volume(struct fscache_volume *volume);
extern void fscache_end_volume_access(struct fscache_volume *volume,
struct fscache_cookie *cookie,
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index b1a962adfd16..1d576bd8112e 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -64,8 +64,12 @@ enum fscache_cookie_trace {
};
enum fscache_access_trace {
+ fscache_access_acquire_volume,
+ fscache_access_acquire_volume_end,
fscache_access_cache_pin,
fscache_access_cache_unpin,
+ fscache_access_relinquish_volume,
+ fscache_access_relinquish_volume_end,
fscache_access_unlive,
};
@@ -96,7 +100,8 @@ enum fscache_access_trace {
EM(fscache_volume_put_hash_collision, "PUT hcoll") \
EM(fscache_volume_put_relinquish, "PUT relnq") \
EM(fscache_volume_see_create_work, "SEE creat") \
- E_(fscache_volume_see_hash_wake, "SEE hwake")
+ EM(fscache_volume_see_hash_wake, "SEE hwake") \
+ E_(fscache_volume_wait_create_work, "WAIT crea")
#define fscache_cookie_traces \
EM(fscache_cookie_collision, "*COLLIDE*") \
@@ -115,8 +120,12 @@ enum fscache_access_trace {
E_(fscache_cookie_see_work, "- work ")
#define fscache_access_traces \
+ EM(fscache_access_acquire_volume, "BEGIN acq_vol") \
+ EM(fscache_access_acquire_volume_end, "END acq_vol") \
EM(fscache_access_cache_pin, "PIN cache ") \
EM(fscache_access_cache_unpin, "UNPIN cache ") \
+ EM(fscache_access_relinquish_volume, "BEGIN rlq_vol") \
+ EM(fscache_access_relinquish_volume_end,"END rlq_vol") \
E_(fscache_access_unlive, "END unlive ")
/*
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