FS-Cache: Allow the current state of all objects to be dumped

Allow the current state of all fscache objects to be dumped by doing:

	cat /proc/fs/fscache/objects

By default, all objects and all fields will be shown.  This can be restricted
by adding a suitable key to one of the caller's keyrings (such as the session
keyring):

	keyctl add user fscache:objlist "<restrictions>" @s

The <restrictions> are:

	K	Show hexdump of object key (don't show if not given)
	A	Show hexdump of object aux data (don't show if not given)

And paired restrictions:

	C	Show objects that have a cookie
	c	Show objects that don't have a cookie
	B	Show objects that are busy
	b	Show objects that aren't busy
	W	Show objects that have pending writes
	w	Show objects that don't have pending writes
	R	Show objects that have outstanding reads
	r	Show objects that don't have outstanding reads
	S	Show objects that have slow work queued
	s	Show objects that don't have slow work queued

If neither side of a restriction pair is given, then both are implied.  For
example:

	keyctl add user fscache:objlist KB @s

shows objects that are busy, and lists their object keys, but does not dump
their auxiliary data.  It also implies "CcWwRrSs", but as 'B' is given, 'b' is
not implied.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 7a9847ccd192..184cbdfbcc99 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -91,6 +91,8 @@ struct fscache_operation {
 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
 #define FSCACHE_OP_DEAD         6       /* op is now dead */
+#define FSCACHE_OP_DEC_READ_CNT 7       /* decrement object->n_reads on destruction */
+#define FSCACHE_OP_KEEP_FLAGS   0xc0    /* flags to keep when repurposing an op */
 
         atomic_t                usage;
         unsigned                debug_id;       /* debugging ID */
@@ -357,6 +359,7 @@ struct fscache_object {
         int                     n_obj_ops;      /* number of object ops outstanding on object */
         int                     n_in_progress;  /* number of ops in progress */
         int                     n_exclusive;    /* number of exclusive ops queued */
+        atomic_t                n_reads;        /* number of read ops in progress */
         spinlock_t              lock;           /* state and operations lock */
 
         unsigned long           lookup_jif;     /* time at which lookup started */
@@ -370,6 +373,7 @@ struct fscache_object {
 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
+#define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
 
         unsigned long           flags;
 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
@@ -385,6 +389,9 @@ struct fscache_object {
         struct list_head        dependents;     /* FIFO of dependent objects */
         struct list_head        dep_link;       /* link in parent's dependents list */
         struct list_head        pending_ops;    /* unstarted operations on this object */
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+        struct rb_node          objlist_link;   /* link in global object list */
+#endif
         pgoff_t                 store_limit;    /* current storage limit */
 };
 
@@ -434,6 +441,12 @@ void fscache_object_init(struct fscache_object *object,
 extern void fscache_object_lookup_negative(struct fscache_object *object);
 extern void fscache_obtained_object(struct fscache_object *object);
 
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+extern void fscache_object_destroy(struct fscache_object *object);
+#else
+#define fscache_object_destroy(object) do {} while(0)
+#endif
+
 /**
  * fscache_object_destroyed - Note destruction of an object in a cache
  * @cache: The cache from which the object came