FS-Cache: Add use of /proc and presentation of statistics

Make FS-Cache create its /proc interface and present various statistical
information through it.  Also provide the functions for updating this
information.

These features are enabled by:

	CONFIG_FSCACHE_PROC
	CONFIG_FSCACHE_STATS
	CONFIG_FSCACHE_HISTOGRAM

The /proc directory for FS-Cache is also exported so that caching modules can
add their own statistics there too.

The FS-Cache module is loadable at this point, and the statistics files can be
examined by userspace:

	cat /proc/fs/fscache/stats
	cat /proc/fs/fscache/histogram

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

2 files changed, 5 insertions, 13 deletions

diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
index 17723053aa9..382d52cdaf2 100644
--- a/Documentation/filesystems/caching/backend-api.txt
+++ b/Documentation/filesystems/caching/backend-api.txt
@@ -100,12 +100,6 @@ A sysfs directory called /sys/fs/fscache/<cachetag>/ is created if CONFIG_SYSFS
 is enabled.  This is accessible through the kobject struct fscache_cache::kobj
 and is for use by the cache as it sees fit.
 
-The cache driver may create itself a directory named for the cache type in the
-/proc/fs/fscache/ directory.  This is available if CONFIG_FSCACHE_PROC is
-enabled and is accessible through:
-
-        struct proc_dir_entry *proc_fscache;
-
 
 ========================
 RELEVANT DATA STRUCTURES
diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index a759d916273..0a751f3c2c7 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -195,7 +195,6 @@ STATISTICAL INFORMATION
 
 If FS-Cache is compiled with the following options enabled:
 
-        CONFIG_FSCACHE_PROC=y (implied by the following two)
         CONFIG_FSCACHE_STATS=y
         CONFIG_FSCACHE_HISTOGRAM=y
 
@@ -275,7 +274,7 @@ proc files.
  (*) /proc/fs/fscache/histogram
 
         cat /proc/fs/fscache/histogram
-        +HZ   +TIME OBJ INST  OP RUNS   OBJ RUNS  RETRV DLY RETRIEVLS
+        JIFS  SECS  OBJ INST  OP RUNS   OBJ RUNS  RETRV DLY RETRIEVLS
         ===== ===== ========= ========= ========= ========= =========
 
      This shows the breakdown of the number of times each amount of time
@@ -291,16 +290,16 @@ proc files.
         RETRIEVLS       Time between beginning and end of a retrieval
 
      Each row shows the number of events that took a particular range of times.
-     Each step is 1 jiffy in size.  The +HZ column indicates the particular
-     jiffy range covered, and the +TIME field the equivalent number of seconds.
+     Each step is 1 jiffy in size.  The JIFS column indicates the particular
+     jiffy range covered, and the SECS field the equivalent number of seconds.
 
 
 =========
 DEBUGGING
 =========
 
-The FS-Cache facility can have runtime debugging enabled by adjusting the value
-in:
+If CONFIG_FSCACHE_DEBUG is enabled, the FS-Cache facility can have runtime
+debugging enabled by adjusting the value in:
 
         /sys/module/fscache/parameters/debug
 
@@ -327,4 +326,3 @@ the control file.  For example:
         echo $((1|8|64)) >/sys/module/fscache/parameters/debug
 
 will turn on all function entry debugging.
-