From: David Howells <dhowells@redhat.com>
To: linux-cachefs@redhat.com
Cc: Jeff Layton <jlayton@kernel.org>,
dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Steve French <sfrench@samba.org>,
Dominique Martinet <asmadeus@codewreck.org>,
Jeff Layton <jlayton@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Omar Sandoval <osandov@osandov.com>,
JeffleXu <jefflexu@linux.alibaba.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
v9fs-developer@lists.sourceforge.net,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 12/68] fscache: Implement volume-level access helpers
Date: Wed, 22 Dec 2021 23:16:55 +0000 [thread overview]
Message-ID: <164021501546.640689.9631510472149608443.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <164021479106.640689.17404516570194656552.stgit@warthog.procyon.org.uk>
Add a pair of helper functions to manage access to a volume, pinning the
volume in place for the duration to prevent cache withdrawal from removing
it:
bool fscache_begin_volume_access(struct fscache_volume *volume,
enum fscache_access_trace why);
void fscache_end_volume_access(struct fscache_volume *volume,
enum fscache_access_trace why);
The way the access gate on the volume works/will work is:
(1) If the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE),
then we return false to indicate access was not permitted.
(2) If the cache tests as live, then we increment the volume's n_accesses
count and then recheck the cache liveness, ending the access if it
ceased to be live.
(3) When we end the access, we decrement the volume's n_accesses and wake
up the any waiters if it reaches 0.
(4) Whilst the cache is caching, the volume's n_accesses is kept
artificially incremented to prevent wakeups from happening.
(5) When the cache is taken offline, the state is changed to prevent new
accesses, the volume's n_accesses is decremented and we wait for it to
become 0.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819594158.215744.8285859817391683254.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906894315.143852.5454793807544710479.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967095028.1823006.9173132503876627466.stgit@warthog.procyon.org.uk/ # v3
---
fs/fscache/internal.h | 3 +
fs/fscache/main.c | 1
fs/fscache/volume.c | 84 ++++++++++++++++++++++++++++++++++++++++
include/linux/fscache-cache.h | 4 ++
include/trace/events/fscache.h | 34 ++++++++++++++++
5 files changed, 126 insertions(+)
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index be29816b37ef..91a4ea08ec0b 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -130,6 +130,9 @@ struct fscache_volume *fscache_get_volume(struct fscache_volume *volume,
enum fscache_volume_trace where);
void fscache_put_volume(struct fscache_volume *volume,
enum fscache_volume_trace where);
+bool fscache_begin_volume_access(struct fscache_volume *volume,
+ struct fscache_cookie *cookie,
+ enum fscache_access_trace why);
void fscache_create_volume(struct fscache_volume *volume, bool wait);
diff --git a/fs/fscache/main.c b/fs/fscache/main.c
index 876f4bee5840..6cab5d99ba4c 100644
--- a/fs/fscache/main.c
+++ b/fs/fscache/main.c
@@ -22,6 +22,7 @@ MODULE_PARM_DESC(fscache_debug,
"FS-Cache debugging mask");
EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
+EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
struct workqueue_struct *fscache_wq;
EXPORT_SYMBOL(fscache_wq);
diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c
index 630894fefd02..20497f0f10bb 100644
--- a/fs/fscache/volume.c
+++ b/fs/fscache/volume.c
@@ -33,6 +33,90 @@ static void fscache_see_volume(struct fscache_volume *volume,
trace_fscache_volume(volume->debug_id, ref, where);
}
+/*
+ * Pin the cache behind a volume so that we can access it.
+ */
+static void __fscache_begin_volume_access(struct fscache_volume *volume,
+ struct fscache_cookie *cookie,
+ enum fscache_access_trace why)
+{
+ int n_accesses;
+
+ n_accesses = atomic_inc_return(&volume->n_accesses);
+ smp_mb__after_atomic();
+ trace_fscache_access_volume(volume->debug_id, cookie ? cookie->debug_id : 0,
+ refcount_read(&volume->ref),
+ n_accesses, why);
+}
+
+/**
+ * fscache_begin_volume_access - Pin a cache so a volume can be accessed
+ * @volume: The volume cookie
+ * @cookie: A datafile cookie for a tracing reference (or NULL)
+ * @why: An indication of the circumstances of the access for tracing
+ *
+ * Attempt to pin the cache to prevent it from going away whilst we're
+ * accessing a volume and returns true if successful. This works as follows:
+ *
+ * (1) If the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE),
+ * then we return false to indicate access was not permitted.
+ *
+ * (2) If the cache tests as live, then we increment the volume's n_accesses
+ * count and then recheck the cache liveness, ending the access if it
+ * ceased to be live.
+ *
+ * (3) When we end the access, we decrement the volume's n_accesses and wake
+ * up the any waiters if it reaches 0.
+ *
+ * (4) Whilst the cache is caching, the volume's n_accesses is kept
+ * artificially incremented to prevent wakeups from happening.
+ *
+ * (5) When the cache is taken offline, the state is changed to prevent new
+ * accesses, the volume's n_accesses is decremented and we wait for it to
+ * become 0.
+ *
+ * The datafile @cookie and the @why indicator are merely provided for tracing
+ * purposes.
+ */
+bool fscache_begin_volume_access(struct fscache_volume *volume,
+ struct fscache_cookie *cookie,
+ enum fscache_access_trace why)
+{
+ if (!fscache_cache_is_live(volume->cache))
+ return false;
+ __fscache_begin_volume_access(volume, cookie, why);
+ if (!fscache_cache_is_live(volume->cache)) {
+ fscache_end_volume_access(volume, cookie, fscache_access_unlive);
+ return false;
+ }
+ return true;
+}
+
+/**
+ * fscache_end_volume_access - Unpin a cache at the end of an access.
+ * @volume: The volume cookie
+ * @cookie: A datafile cookie for a tracing reference (or NULL)
+ * @why: An indication of the circumstances of the access for tracing
+ *
+ * Unpin a cache volume after we've accessed it. The datafile @cookie and the
+ * @why indicator are merely provided for tracing purposes.
+ */
+void fscache_end_volume_access(struct fscache_volume *volume,
+ struct fscache_cookie *cookie,
+ enum fscache_access_trace why)
+{
+ int n_accesses;
+
+ smp_mb__before_atomic();
+ n_accesses = atomic_dec_return(&volume->n_accesses);
+ trace_fscache_access_volume(volume->debug_id, cookie ? cookie->debug_id : 0,
+ refcount_read(&volume->ref),
+ n_accesses, why);
+ if (n_accesses == 0)
+ wake_up_var(&volume->n_accesses);
+}
+EXPORT_SYMBOL(fscache_end_volume_access);
+
static bool fscache_volume_same(const struct fscache_volume *a,
const struct fscache_volume *b)
{
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index c4355b888c91..fbbd8a2afe12 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -53,6 +53,10 @@ extern struct rw_semaphore fscache_addremove_sem;
extern struct fscache_cache *fscache_acquire_cache(const char *name);
extern void fscache_relinquish_cache(struct fscache_cache *cache);
+extern void fscache_end_volume_access(struct fscache_volume *volume,
+ struct fscache_cookie *cookie,
+ enum fscache_access_trace why);
+
extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie,
enum fscache_cookie_trace where);
extern void fscache_put_cookie(struct fscache_cookie *cookie,
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index 734966bc49e1..4f40cfa52469 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -43,6 +43,7 @@ enum fscache_volume_trace {
fscache_volume_put_relinquish,
fscache_volume_see_create_work,
fscache_volume_see_hash_wake,
+ fscache_volume_wait_create_work,
};
enum fscache_cookie_trace {
@@ -245,6 +246,39 @@ TRACE_EVENT(fscache_access_cache,
__entry->n_accesses)
);
+TRACE_EVENT(fscache_access_volume,
+ TP_PROTO(unsigned int volume_debug_id,
+ unsigned int cookie_debug_id,
+ int ref,
+ int n_accesses,
+ enum fscache_access_trace why),
+
+ TP_ARGS(volume_debug_id, cookie_debug_id, ref, n_accesses, why),
+
+ TP_STRUCT__entry(
+ __field(unsigned int, volume )
+ __field(unsigned int, cookie )
+ __field(int, ref )
+ __field(int, n_accesses )
+ __field(enum fscache_access_trace, why )
+ ),
+
+ TP_fast_assign(
+ __entry->volume = volume_debug_id;
+ __entry->cookie = cookie_debug_id;
+ __entry->ref = ref;
+ __entry->n_accesses = n_accesses;
+ __entry->why = why;
+ ),
+
+ TP_printk("V=%08x c=%08x %s r=%d a=%d",
+ __entry->volume,
+ __entry->cookie,
+ __print_symbolic(__entry->why, fscache_access_traces),
+ __entry->ref,
+ __entry->n_accesses)
+ );
+
TRACE_EVENT(fscache_acquire,
TP_PROTO(struct fscache_cookie *cookie),
next prev parent reply other threads:[~2021-12-22 23:17 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-22 23:13 [PATCH v4 00/68] fscache, cachefiles: Rewrite David Howells
2021-12-22 23:13 ` [PATCH v4 01/68] fscache, cachefiles: Disable configuration David Howells
2021-12-22 23:13 ` [PATCH v4 02/68] cachefiles: Delete the cachefiles driver pending rewrite David Howells
2021-12-22 23:14 ` [PATCH v4 03/68] fscache: Remove the contents of the fscache driver, " David Howells
2021-12-22 23:14 ` [PATCH v4 04/68] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells
2021-12-22 23:14 ` [PATCH v4 05/68] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells
2021-12-22 23:15 ` [PATCH v4 06/68] fscache: Introduce new driver David Howells
2021-12-22 23:15 ` [PATCH v4 07/68] fscache: Implement a hash function David Howells
2021-12-22 23:15 ` [PATCH v4 08/68] fscache: Implement cache registration David Howells
2021-12-22 23:15 ` [PATCH v4 09/68] fscache: Implement volume registration David Howells
2021-12-22 23:16 ` [PATCH v4 10/68] fscache: Implement cookie registration David Howells
2021-12-22 23:16 ` [PATCH v4 11/68] fscache: Implement cache-level access helpers David Howells
2021-12-22 23:16 ` David Howells [this message]
2021-12-22 23:17 ` [PATCH v4 13/68] fscache: Implement cookie-level " David Howells
2021-12-22 23:17 ` [PATCH v4 14/68] fscache: Implement functions add/remove a cache David Howells
2021-12-22 23:17 ` [PATCH v4 15/68] fscache: Provide and use cache methods to lookup/create/free a volume David Howells
2021-12-22 23:18 ` [PATCH v4 16/68] fscache: Add a function for a cache backend to note an I/O error David Howells
2021-12-22 23:18 ` [PATCH v4 17/68] fscache: Implement simple cookie state machine David Howells
2021-12-22 23:18 ` [PATCH v4 18/68] fscache: Implement cookie user counting and resource pinning David Howells
2021-12-22 23:18 ` [PATCH v4 19/68] fscache: Implement cookie invalidation David Howells
2021-12-22 23:18 ` [PATCH v4 20/68] fscache: Provide a means to begin an operation David Howells
2021-12-22 23:19 ` [PATCH v4 21/68] fscache: Count data storage objects in a cache David Howells
2021-12-22 23:19 ` [PATCH v4 22/68] fscache: Provide read/write stat counters for the cache David Howells
2021-12-22 23:19 ` [PATCH v4 23/68] fscache: Provide a function to let the netfs update its coherency data David Howells
2021-12-22 23:19 ` [PATCH v4 24/68] netfs: Pass more information on how to deal with a hole in the cache David Howells
2021-12-22 23:20 ` [PATCH v4 25/68] fscache: Implement raw I/O interface David Howells
2021-12-22 23:20 ` [PATCH v4 26/68] fscache: Implement higher-level write " David Howells
2021-12-22 23:20 ` [PATCH v4 27/68] vfs, fscache: Implement pinning of cache usage for writeback David Howells
2021-12-22 23:20 ` [PATCH v4 28/68] fscache: Provide a function to note the release of a page David Howells
2022-01-06 15:55 ` Jeff Layton
2022-01-06 16:26 ` David Howells
2021-12-22 23:21 ` [PATCH v4 29/68] fscache: Provide a function to resize a cookie David Howells
2021-12-22 23:21 ` [PATCH v4 30/68] cachefiles: Introduce rewritten driver David Howells
2021-12-22 23:21 ` [PATCH v4 31/68] cachefiles: Define structs David Howells
2021-12-22 23:22 ` [PATCH v4 32/68] cachefiles: Add some error injection support David Howells
2021-12-22 23:22 ` [PATCH v4 33/68] cachefiles: Add a couple of tracepoints for logging errors David Howells
2021-12-22 23:22 ` [PATCH v4 34/68] cachefiles: Add cache error reporting macro David Howells
2021-12-22 23:22 ` [PATCH v4 35/68] cachefiles: Add security derivation David Howells
2021-12-22 23:23 ` [PATCH v4 36/68] cachefiles: Register a miscdev and parse commands over it David Howells
2021-12-22 23:23 ` [PATCH v4 37/68] cachefiles: Provide a function to check how much space there is David Howells
2021-12-22 23:23 ` [PATCH v4 38/68] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells
2022-01-06 17:04 ` Jeff Layton
2022-01-08 7:08 ` Amir Goldstein
2022-01-08 7:17 ` Matthew Wilcox
2022-01-10 7:53 ` Christoph Hellwig
2022-01-10 11:31 ` David Howells
2022-01-08 8:43 ` David Howells
2022-01-08 8:41 ` David Howells
2021-12-22 23:23 ` [PATCH v4 39/68] cachefiles: Implement a function to get/create a directory in the cache David Howells
2021-12-22 23:23 ` [PATCH v4 40/68] cachefiles: Implement cache registration and withdrawal David Howells
2022-01-06 17:17 ` Jeff Layton
2022-01-06 17:44 ` David Howells
2021-12-22 23:24 ` [PATCH v4 41/68] cachefiles: Implement volume support David Howells
2021-12-22 23:24 ` [PATCH v4 42/68] cachefiles: Add tracepoints for calls to the VFS David Howells
2021-12-22 23:24 ` [PATCH v4 43/68] cachefiles: Implement object lifecycle funcs David Howells
2021-12-22 23:24 ` [PATCH v4 44/68] cachefiles: Implement key to filename encoding David Howells
2022-01-06 17:43 ` Jeff Layton
2022-01-07 11:19 ` David Howells
2021-12-22 23:25 ` [PATCH v4 45/68] cachefiles: Implement metadata/coherency data storage in xattrs David Howells
2021-12-22 23:25 ` [PATCH v4 46/68] cachefiles: Mark a backing file in use with an inode flag David Howells
2022-01-06 18:04 ` Jeff Layton
2022-01-07 11:25 ` David Howells
2021-12-22 23:25 ` [PATCH v4 47/68] cachefiles: Implement culling daemon commands David Howells
2021-12-22 23:26 ` [PATCH v4 48/68] cachefiles: Implement backing file wrangling David Howells
2021-12-22 23:26 ` [PATCH v4 49/68] cachefiles: Implement begin and end I/O operation David Howells
2021-12-22 23:26 ` [PATCH v4 50/68] cachefiles: Implement cookie resize for truncate David Howells
2021-12-22 23:27 ` [PATCH v4 51/68] cachefiles: Implement the I/O routines David Howells
2021-12-22 23:27 ` [PATCH v4 52/68] fscache, cachefiles: Store the volume coherency data David Howells
2021-12-22 23:27 ` [PATCH v4 53/68] cachefiles: Allow cachefiles to actually function David Howells
2021-12-22 23:27 ` [PATCH v4 54/68] fscache, cachefiles: Display stats of no-space events David Howells
2021-12-22 23:27 ` [PATCH v4 55/68] fscache, cachefiles: Display stat of culling events David Howells
2021-12-22 23:28 ` [PATCH v4 56/68] afs: Convert afs to use the new fscache API David Howells
2021-12-22 23:28 ` [PATCH v4 57/68] afs: Copy local writes to the cache when writing to the server David Howells
2021-12-22 23:28 ` [PATCH v4 58/68] afs: Skip truncation on the server of data we haven't written yet David Howells
2021-12-22 23:28 ` [PATCH v4 59/68] 9p: Use fscache indexing rewrite and reenable caching David Howells
2021-12-22 23:29 ` [PATCH v4 60/68] 9p: Copy local writes to the cache when writing to the server David Howells
2021-12-22 23:29 ` [PATCH v4 61/68] nfs: Convert to new fscache volume/cookie API David Howells
2021-12-22 23:29 ` [PATCH v4 62/68] nfs: Implement cache I/O by accessing the cache directly David Howells
2021-12-22 23:29 ` [PATCH v4 63/68] cifs: Support fscache indexing rewrite (untested) David Howells
2021-12-22 23:30 ` [PATCH v4 64/68] ceph: conversion to new fscache API David Howells
2021-12-22 23:30 ` [PATCH v4 65/68] ceph: add fscache writeback support David Howells
2021-12-22 23:30 ` [PATCH v4 66/68] fscache: Rewrite documentation David Howells
2021-12-22 23:31 ` [PATCH v4 67/68] fscache: Add a tracepoint for cookie use/unuse David Howells
2021-12-22 23:31 ` [PATCH v4 68/68] 9p, afs, ceph, cifs, nfs: Use current_is_kswapd() rather than gfpflags_allow_blocking() David Howells
2022-01-04 10:50 ` [PATCH v4 00/68] fscache, cachefiles: Rewrite Jeff Layton
2022-01-04 11:27 ` David Wysochanski
2022-01-06 18:19 ` [Linux-cachefs] " Marc Dionne
2022-01-06 18:29 ` Jeff Layton
2022-01-07 21:52 ` [PATCH v4 63/68] cifs: Support fscache indexing rewrite (untested) David Howells
2022-01-09 15:27 ` Jeff Layton
2022-01-07 22:16 ` [PATCH v5 63/68] cifs: Support fscache indexing rewrite David Howells
2022-01-10 11:21 ` [PATCH v4 00/68] fscache, cachefiles: Rewrite Dominique Martinet
2022-01-12 7:20 ` [PATCH v5 63/68] cifs: Support fscache indexing rewrite David Howells
2022-01-12 21:56 ` [PATCH v6] " David Howells
2022-01-13 16:20 ` David Howells
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