FS-Cache: Provide proper invalidation

Provide a proper invalidation method rather than relying on the netfs retiring
the cookie it has and getting a new one.  The problem with this is that isn't
easy for the netfs to make sure that it has completed/cancelled all its
outstanding storage and retrieval operations on the cookie it is retiring.

Instead, have the cache provide an invalidation method that will cancel or wait
for all currently outstanding operations before invalidating the cache, and
will cause new operations to queue up behind that.  Whilst invalidation is in
progress, some requests will be rejected until the cache can stack a barrier on
the operation queue to cause new operations to be deferred behind it.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 4765190d537f..51cdaee14109 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -80,6 +80,9 @@ atomic_t fscache_n_acquires_ok;
 atomic_t fscache_n_acquires_nobufs;
 atomic_t fscache_n_acquires_oom;
 
+atomic_t fscache_n_invalidates;
+atomic_t fscache_n_invalidates_run;
+
 atomic_t fscache_n_updates;
 atomic_t fscache_n_updates_null;
 atomic_t fscache_n_updates_run;
@@ -112,6 +115,7 @@ atomic_t fscache_n_cop_alloc_object;
 atomic_t fscache_n_cop_lookup_object;
 atomic_t fscache_n_cop_lookup_complete;
 atomic_t fscache_n_cop_grab_object;
+atomic_t fscache_n_cop_invalidate_object;
 atomic_t fscache_n_cop_update_object;
 atomic_t fscache_n_cop_drop_object;
 atomic_t fscache_n_cop_put_object;
@@ -168,6 +172,10 @@ static int fscache_stats_show(struct seq_file *m, void *v)
                    atomic_read(&fscache_n_object_created),
                    atomic_read(&fscache_n_object_lookups_timed_out));
 
+        seq_printf(m, "Invals : n=%u run=%u\n",
+                   atomic_read(&fscache_n_invalidates),
+                   atomic_read(&fscache_n_invalidates_run));
+
         seq_printf(m, "Updates: n=%u nul=%u run=%u\n",
                    atomic_read(&fscache_n_updates),
                    atomic_read(&fscache_n_updates_null),
@@ -246,7 +254,8 @@ static int fscache_stats_show(struct seq_file *m, void *v)
                    atomic_read(&fscache_n_cop_lookup_object),
                    atomic_read(&fscache_n_cop_lookup_complete),
                    atomic_read(&fscache_n_cop_grab_object));
-        seq_printf(m, "CacheOp: upo=%d dro=%d pto=%d atc=%d syn=%d\n",
+        seq_printf(m, "CacheOp: inv=%d upo=%d dro=%d pto=%d atc=%d syn=%d\n",
+                   atomic_read(&fscache_n_cop_invalidate_object),
                    atomic_read(&fscache_n_cop_update_object),
                    atomic_read(&fscache_n_cop_drop_object),
                    atomic_read(&fscache_n_cop_put_object),