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Commit 182d919b authored by David Howells's avatar David Howells
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FS-Cache: Count culled objects and objects rejected due to lack of space 



Count the number of objects that get culled by the cache backend and the
number of objects that the cache backend declines to instantiate due to lack
of space in the cache.

These numbers are made available through /proc/fs/fscache/stats

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarSteve Dickson <steved@redhat.com>
Acked-by: default avatarJeff Layton <jeff.layton@primarydata.com>
parent b2b89ebf

Documentation/filesystems/caching/backend-api.txt

+23 −0
Original line number Diff line number Diff line
@@ -676,6 +676,29 @@ FS-Cache provides some utilities that a cache backend may make use of: 
     as possible.





 (*) Indicate that a stale object was found and discarded:



	void fscache_object_retrying_stale(struct fscache_object *object);



     This is called to indicate that the lookup procedure found an object in

     the cache that the netfs decided was stale.  The object has been

     discarded from the cache and the lookup will be performed again.





 (*) Indicate that the caching backend killed an object:



	void fscache_object_mark_killed(struct fscache_object *object,

					enum fscache_why_object_killed why);



     This is called to indicate that the cache backend preemptively killed an

     object.  The why parameter should be set to indicate the reason:



	FSCACHE_OBJECT_IS_STALE - the object was stale and needs discarding.

	FSCACHE_OBJECT_NO_SPACE - there was insufficient cache space

	FSCACHE_OBJECT_WAS_RETIRED - the object was retired when relinquished.

	FSCACHE_OBJECT_WAS_CULLED - the object was culled to make space.





 (*) Get and release references on a retrieval record:



	void fscache_get_retrieval(struct fscache_retrieval *op);

Documentation/filesystems/caching/fscache.txt

+4 −0
Original line number Diff line number Diff line
@@ -303,6 +303,10 @@ proc files. 
		wrp=N	Number of in-progress write_page() cache ops

		ucp=N	Number of in-progress uncache_page() cache ops

		dsp=N	Number of in-progress dissociate_pages() cache ops

	CacheEv	nsp=N	Number of object lookups/creations rejected due to lack of space

		stl=N	Number of stale objects deleted

		rtr=N	Number of objects retired when relinquished

		cul=N	Number of objects culled





 (*) /proc/fs/fscache/histogram

fs/cachefiles/internal.h

+0 −1
Original line number Diff line number Diff line
@@ -43,7 +43,6 @@ struct cachefiles_object { 
	loff_t				i_size;		/* object size */

	unsigned long			flags;

#define CACHEFILES_OBJECT_ACTIVE	0		/* T if marked active */

#define CACHEFILES_OBJECT_BURIED	1		/* T if preemptively buried */

	atomic_t			usage;		/* object usage count */

	uint8_t				type;		/* object type */

	uint8_t				new;		/* T if object new */

fs/cachefiles/namei.c

+21 −12
Original line number Diff line number Diff line
@@ -97,7 +97,8 @@ static noinline void cachefiles_printk_object(struct cachefiles_object *object, 
 *   call vfs_unlink(), vfs_rmdir() or vfs_rename()

 */

static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,

					  struct dentry *dentry)

					  struct dentry *dentry,

					  enum fscache_why_object_killed why)

{

	struct cachefiles_object *object;

	struct rb_node *p;
@@ -132,8 +133,9 @@ static void cachefiles_mark_object_buried(struct cachefiles_cache *cache, 
		pr_err("\n");

		pr_err("Error: Can't preemptively bury live object\n");

		cachefiles_printk_object(object, NULL);

	} else if (test_and_set_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {

		pr_err("Error: Object already preemptively buried\n");

	} else {

		if (why != FSCACHE_OBJECT_IS_STALE)

			fscache_object_mark_killed(&object->fscache, why);

	}



	write_unlock(&cache->active_lock);
@@ -265,7 +267,8 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache, 
static int cachefiles_bury_object(struct cachefiles_cache *cache,

				  struct dentry *dir,

				  struct dentry *rep,

				  bool preemptive)

				  bool preemptive,

				  enum fscache_why_object_killed why)

{

	struct dentry *grave, *trap;

	struct path path, path_to_graveyard;
@@ -289,7 +292,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache, 
			ret = vfs_unlink(dir->d_inode, rep, NULL);



			if (preemptive)

				cachefiles_mark_object_buried(cache, rep);

				cachefiles_mark_object_buried(cache, rep, why);

		}



		mutex_unlock(&dir->d_inode->i_mutex);
@@ -394,7 +397,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache, 
					    "Rename failed with error %d", ret);



		if (preemptive)

			cachefiles_mark_object_buried(cache, rep);

			cachefiles_mark_object_buried(cache, rep, why);

	}



	unlock_rename(cache->graveyard, dir);
@@ -422,7 +425,7 @@ int cachefiles_delete_object(struct cachefiles_cache *cache, 


	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);



	if (test_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {

	if (test_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->fscache.flags)) {

		/* object allocation for the same key preemptively deleted this

		 * object's file so that it could create its own file */

		_debug("object preemptively buried");
@@ -433,7 +436,8 @@ int cachefiles_delete_object(struct cachefiles_cache *cache, 
		 * may have been renamed */

		if (dir == object->dentry->d_parent) {

			ret = cachefiles_bury_object(cache, dir,

						     object->dentry, false);

						     object->dentry, false,

						     FSCACHE_OBJECT_WAS_RETIRED);

		} else {

			/* it got moved, presumably by cachefilesd culling it,

			 * so it's no longer in the key path and we can ignore
@@ -522,7 +526,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent, 
		if (!next->d_inode) {

			ret = cachefiles_has_space(cache, 1, 0);

			if (ret < 0)

				goto create_error;

				goto no_space_error;



			path.dentry = dir;

			ret = security_path_mkdir(&path, next, 0);
@@ -551,7 +555,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent, 
		if (!next->d_inode) {

			ret = cachefiles_has_space(cache, 1, 0);

			if (ret < 0)

				goto create_error;

				goto no_space_error;



			path.dentry = dir;

			ret = security_path_mknod(&path, next, S_IFREG, 0);
@@ -602,7 +606,8 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent, 
			 * mutex) */

			object->dentry = NULL;



			ret = cachefiles_bury_object(cache, dir, next, true);

			ret = cachefiles_bury_object(cache, dir, next, true,

						     FSCACHE_OBJECT_IS_STALE);

			dput(next);

			next = NULL;
@@ -610,6 +615,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent, 
				goto delete_error;



			_debug("redo lookup");

			fscache_object_retrying_stale(&object->fscache);

			goto lookup_again;

		}

	}
@@ -662,6 +668,8 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent, 
	_leave(" = 0 [%lu]", object->dentry->d_inode->i_ino);

	return 0;



no_space_error:

	fscache_object_mark_killed(&object->fscache, FSCACHE_OBJECT_NO_SPACE);

create_error:

	_debug("create error %d", ret);

	if (ret == -EIO)
@@ -927,7 +935,8 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir, 
	/*  actually remove the victim (drops the dir mutex) */

	_debug("bury");



	ret = cachefiles_bury_object(cache, dir, victim, false);

	ret = cachefiles_bury_object(cache, dir, victim, false,

				     FSCACHE_OBJECT_WAS_CULLED);

	if (ret < 0)

		goto error;

fs/fscache/internal.h

+5 −0
Original line number Diff line number Diff line
@@ -271,6 +271,11 @@ extern atomic_t fscache_n_cop_write_page; 
extern atomic_t fscache_n_cop_uncache_page;

extern atomic_t fscache_n_cop_dissociate_pages;



extern atomic_t fscache_n_cache_no_space_reject;

extern atomic_t fscache_n_cache_stale_objects;

extern atomic_t fscache_n_cache_retired_objects;

extern atomic_t fscache_n_cache_culled_objects;



static inline void fscache_stat(atomic_t *stat)

{

	atomic_inc(stat);