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Subject[PATCH v3 54/68] fscache, cachefiles: Display stats of no-space events
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Date
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@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819653216.215744.17210522251617386509.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906958369.143852.7257100711818401748.stgit@warthog.procyon.org.uk/ # v2
---

fs/cachefiles/cache.c | 18 +++++++++++++++---
fs/cachefiles/daemon.c | 2 +-
fs/cachefiles/internal.h | 11 +++++++++--
fs/cachefiles/io.c | 7 +++++--
fs/cachefiles/namei.c | 6 ++++--
fs/fscache/stats.c | 8 ++++++++
include/linux/fscache-cache.h | 6 ++++++
7 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/fs/cachefiles/cache.c b/fs/cachefiles/cache.c
index e2cbbc08bad9..809519286335 100644
--- a/fs/cachefiles/cache.c
+++ b/fs/cachefiles/cache.c
@@ -147,7 +147,7 @@ int cachefiles_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;
@@ -175,7 +175,8 @@ int cachefiles_add_cache(struct cachefiles_cache *cache)
* 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;
u64 b_avail, b_writing;
@@ -233,7 +234,7 @@ int cachefiles_has_space(struct cachefiles_cache *cache,
ret = -ENOBUFS;
if (stats.f_ffree < cache->fstop ||
b_avail < cache->bstop)
- goto begin_cull;
+ goto stop_and_begin_cull;

ret = 0;
if (stats.f_ffree < cache->fcull ||
@@ -252,6 +253,17 @@ 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/daemon.c b/fs/cachefiles/daemon.c
index 45af558a696e..40a792421fc1 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -170,7 +170,7 @@ 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);
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index abdd1b66f6b9..8dd54d9375b6 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -130,10 +130,17 @@ static inline void cachefiles_state_changed(struct cachefiles_cache *cache)
* cache.c
*/
extern int cachefiles_add_cache(struct cachefiles_cache *cache);
-extern int cachefiles_has_space(struct cachefiles_cache *cache,
- unsigned fnr, unsigned bnr);
extern void cachefiles_withdraw_cache(struct cachefiles_cache *cache);

+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,
+ enum cachefiles_has_space_for reason);
+
/*
* daemon.c
*/
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 6f4dce0cfc36..60b1eac2ce78 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -468,7 +468,8 @@ 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();
@@ -483,6 +484,7 @@ 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();
ret = cachefiles_inject_remove_error();
if (ret == 0)
ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
@@ -498,7 +500,8 @@ 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,
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index b549e9f79c01..ab3ca598acac 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -115,7 +115,8 @@ 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)) {
- 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;

@@ -513,7 +514,8 @@ 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;

diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 798ee68b3e9d..db2f4e225dd9 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -42,6 +42,10 @@ 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
@@ -82,6 +86,10 @@ 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 3fa4902dc87c..007e47f38610 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -186,11 +186,17 @@ static inline void fscache_wait_for_objects(struct fscache_cache *cache)
#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

#endif /* _LINUX_FSCACHE_CACHE_H */

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