[PATCH v2 52/53] fscache, cachefiles: Display stats of no-space events

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Add stat counters of no-space events that caused caching not to happen and
display in /proc/fs/fscache/stats.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
---

 fs/cachefiles/bind.c          |    2 +-
 fs/cachefiles/daemon.c        |   18 +++++++++++++++---
 fs/cachefiles/internal.h      |    8 +++++++-
 fs/cachefiles/io.c            |    9 ++++++---
 fs/cachefiles/namei.c         |    6 ++++--
 fs/fscache/stats.c            |    8 ++++++++
 include/linux/fscache-cache.h |    6 ++++++
 7 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/fs/cachefiles/bind.c b/fs/cachefiles/bind.c
index 59c9d141f1fe..a62361e82b20 100644
--- a/fs/cachefiles/bind.c
+++ b/fs/cachefiles/bind.c
@@ -211,7 +211,7 @@ static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
 	pr_info("File cache on %s registered\n", cache_cookie->name);
 
 	/* check how much space the cache has */
-	cachefiles_has_space(cache, 0, 0);
+	cachefiles_has_space(cache, 0, 0, cachefiles_has_space_check);
 	cachefiles_end_secure(cache, saved_cred);
 	_leave(" = 0 [%px]", cache->cache);
 	return 0;
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index 50ec292c7213..7a7d521aeb83 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -168,7 +168,7 @@ static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
 		return 0;
 
 	/* check how much space the cache has */
-	cachefiles_has_space(cache, 0, 0);
+	cachefiles_has_space(cache, 0, 0, cachefiles_has_space_check);
 
 	/* summarise */
 	f_released = atomic_xchg(&cache->f_released, 0);
@@ -668,7 +668,8 @@ static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
  * cache
  */
 int cachefiles_has_space(struct cachefiles_cache *cache,
-			 unsigned fnr, unsigned bnr)
+			 unsigned fnr, unsigned bnr,
+			 enum cachefiles_has_space_for reason)
 {
 	struct kstatfs stats;
 	int ret;
@@ -720,7 +721,7 @@ int cachefiles_has_space(struct cachefiles_cache *cache,
 	ret = -ENOBUFS;
 	if (stats.f_ffree < cache->fstop ||
 	    stats.f_bavail < cache->bstop)
-		goto begin_cull;
+		goto stop_and_begin_cull;
 
 	ret = 0;
 	if (stats.f_ffree < cache->fcull ||
@@ -739,6 +740,17 @@ int cachefiles_has_space(struct cachefiles_cache *cache,
 	//_leave(" = 0");
 	return 0;
 
+stop_and_begin_cull:
+	switch (reason) {
+	case cachefiles_has_space_for_write:
+		fscache_count_no_write_space();
+		break;
+	case cachefiles_has_space_for_create:
+		fscache_count_no_create_space();
+		break;
+	default:
+		break;
+	}
 begin_cull:
 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
 		_debug("### CULL CACHE ###");
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index d3c7db3b058e..8d1b1347abb4 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -152,8 +152,14 @@ extern void cachefiles_daemon_unbind(struct cachefiles_cache *cache);
  */
 extern const struct file_operations cachefiles_daemon_fops;
 
+enum cachefiles_has_space_for {
+	cachefiles_has_space_check,
+	cachefiles_has_space_for_write,
+	cachefiles_has_space_for_create,
+};
 extern int cachefiles_has_space(struct cachefiles_cache *cache,
-				unsigned fnr, unsigned bnr);
+				unsigned fnr, unsigned bnr,
+				enum cachefiles_has_space_for reason);
 
 /*
  * error_inject.c
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 78e6ef781f73..cb531424a64f 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -461,7 +461,8 @@ static int __cachefiles_prepare_write(struct netfs_cache_resources *cres,
 	 * space, we need to see if it's fully allocated.  If it's not, we may
 	 * want to cull it.
 	 */
-	if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE) == 0)
+	if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
+				 cachefiles_has_space_check) == 0)
 		return 0; /* Enough space to simply overwrite the whole block */
 
 	pos = cachefiles_inject_read_error();
@@ -476,6 +477,7 @@ static int __cachefiles_prepare_write(struct netfs_cache_resources *cres,
 		return 0; /* Fully allocated */
 
 	/* Partially allocated, but insufficient space: cull. */
+	fscache_count_no_write_space();
 	pos = cachefiles_inject_remove_error();
 	if (pos == 0)
 		ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
@@ -491,7 +493,8 @@ static int __cachefiles_prepare_write(struct netfs_cache_resources *cres,
 	return ret;
 
 check_space:
-	return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE);
+	return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
+				    cachefiles_has_space_for_write);
 }
 
 static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
@@ -528,7 +531,7 @@ static int cachefiles_prepare_fallback_write(struct netfs_cache_resources *cres,
 
 	_enter("%lx", index);
 
-	return cachefiles_has_space(cache, 0, 1);
+	return cachefiles_has_space(cache, 0, 1, cachefiles_has_space_for_write);
 }
 
 /*
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index ad87fb28b602..9b0a14e37cfa 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -309,7 +309,8 @@ static bool cachefiles_create_file(struct cachefiles_object *object)
 	struct file *file;
 	int ret;
 
-	ret = cachefiles_has_space(object->volume->cache, 1, 0);
+	ret = cachefiles_has_space(object->volume->cache, 1, 0,
+				   cachefiles_has_space_for_create);
 	if (ret < 0)
 		return false;
 
@@ -480,7 +481,8 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 	/* we need to create the subdir if it doesn't exist yet */
 	if (d_is_negative(subdir)) {
 		if (cache->store) {
-			ret = cachefiles_has_space(cache, 1, 0);
+			ret = cachefiles_has_space(cache, 1, 0,
+						   cachefiles_has_space_for_create);
 			if (ret < 0)
 				goto mkdir_error;
 		}
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 225bba60b617..d34fb6e91d57 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -44,6 +44,10 @@ atomic_t fscache_n_read;
 EXPORT_SYMBOL(fscache_n_read);
 atomic_t fscache_n_write;
 EXPORT_SYMBOL(fscache_n_write);
+atomic_t fscache_n_no_write_space;
+EXPORT_SYMBOL(fscache_n_no_write_space);
+atomic_t fscache_n_no_create_space;
+EXPORT_SYMBOL(fscache_n_no_create_space);
 
 /*
  * display the general statistics
@@ -86,6 +90,10 @@ int fscache_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&fscache_n_relinquishes_retire),
 		   atomic_read(&fscache_n_relinquishes_dropped));
 
+	seq_printf(m, "NoSpace: nwr=%u ncr=%u\n",
+		   atomic_read(&fscache_n_no_write_space),
+		   atomic_read(&fscache_n_no_create_space));
+
 	seq_printf(m, "IO     : rd=%u wr=%u\n",
 		   atomic_read(&fscache_n_read),
 		   atomic_read(&fscache_n_write));
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index d5f6b636175e..7b3225c6c22f 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -179,11 +179,17 @@ void fscache_end_operation(struct netfs_cache_resources *cres)
 #ifdef CONFIG_FSCACHE_STATS
 extern atomic_t fscache_n_read;
 extern atomic_t fscache_n_write;
+extern atomic_t fscache_n_no_write_space;
+extern atomic_t fscache_n_no_create_space;
 #define fscache_count_read() atomic_inc(&fscache_n_read)
 #define fscache_count_write() atomic_inc(&fscache_n_write)
+#define fscache_count_no_write_space() atomic_inc(&fscache_n_no_write_space)
+#define fscache_count_no_create_space() atomic_inc(&fscache_n_no_create_space)
 #else
 #define fscache_count_read() do {} while(0)
 #define fscache_count_write() do {} while(0)
+#define fscache_count_no_write_space() do {} while(0)
+#define fscache_count_no_create_space() do {} while(0)
 #endif
 
 extern struct workqueue_struct *fscache_wq;





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