linux/fs/fscache/object.c
David Howells fee096deb4 CacheFiles: Catch an overly long wait for an old active object
Catch an overly long wait for an old, dying active object when we want to
replace it with a new one.  The probability is that all the slow-work threads
are hogged, and the delete can't get a look in.

What we do instead is:

 (1) if there's nothing in the slow work queue, we sleep until either the dying
     object has finished dying or there is something in the slow work queue
     behind which we can queue our object.

 (2) if there is something in the slow work queue, we return ETIMEDOUT to
     fscache_lookup_object(), which then puts us back on the slow work queue,
     presumably behind the deletion that we're blocked by.  We are then
     deferred for a while until we work our way back through the queue -
     without blocking a slow-work thread unnecessarily.

A backtrace similar to the following may appear in the log without this patch:

	INFO: task kslowd004:5711 blocked for more than 120 seconds.
	"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
	kslowd004     D 0000000000000000     0  5711      2 0x00000080
	 ffff88000340bb80 0000000000000046 ffff88002550d000 0000000000000000
	 ffff88002550d000 0000000000000007 ffff88000340bfd8 ffff88002550d2a8
	 000000000000ddf0 00000000000118c0 00000000000118c0 ffff88002550d2a8
	Call Trace:
	 [<ffffffff81058e21>] ? trace_hardirqs_on+0xd/0xf
	 [<ffffffffa011c4d8>] ? cachefiles_wait_bit+0x0/0xd [cachefiles]
	 [<ffffffffa011c4e1>] cachefiles_wait_bit+0x9/0xd [cachefiles]
	 [<ffffffff81353153>] __wait_on_bit+0x43/0x76
	 [<ffffffff8111ae39>] ? ext3_xattr_get+0x1ec/0x270
	 [<ffffffff813531ef>] out_of_line_wait_on_bit+0x69/0x74
	 [<ffffffffa011c4d8>] ? cachefiles_wait_bit+0x0/0xd [cachefiles]
	 [<ffffffff8104c125>] ? wake_bit_function+0x0/0x2e
	 [<ffffffffa011bc79>] cachefiles_mark_object_active+0x203/0x23b [cachefiles]
	 [<ffffffffa011c209>] cachefiles_walk_to_object+0x558/0x827 [cachefiles]
	 [<ffffffffa011a429>] cachefiles_lookup_object+0xac/0x12a [cachefiles]
	 [<ffffffffa00aa1e9>] fscache_lookup_object+0x1c7/0x214 [fscache]
	 [<ffffffffa00aafc5>] fscache_object_state_machine+0xa5/0x52d [fscache]
	 [<ffffffffa00ab4ac>] fscache_object_slow_work_execute+0x5f/0xa0 [fscache]
	 [<ffffffff81082093>] slow_work_execute+0x18f/0x2d1
	 [<ffffffff8108239a>] slow_work_thread+0x1c5/0x308
	 [<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
	 [<ffffffff810821d5>] ? slow_work_thread+0x0/0x308
	 [<ffffffff8104be91>] kthread+0x7a/0x82
	 [<ffffffff8100beda>] child_rip+0xa/0x20
	 [<ffffffff8100b87c>] ? restore_args+0x0/0x30
	 [<ffffffff8104be17>] ? kthread+0x0/0x82
	 [<ffffffff8100bed0>] ? child_rip+0x0/0x20
	1 lock held by kslowd004/5711:
	 #0:  (&sb->s_type->i_mutex_key#7/1){+.+.+.}, at: [<ffffffffa011be64>] cachefiles_walk_to_object+0x1b3/0x827 [cachefiles]

Signed-off-by: David Howells <dhowells@redhat.com>
2009-11-19 18:12:05 +00:00

893 lines
26 KiB
C

/* FS-Cache object state machine handler
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* See Documentation/filesystems/caching/object.txt for a description of the
* object state machine and the in-kernel representations.
*/
#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include <linux/seq_file.h>
#include "internal.h"
const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
[FSCACHE_OBJECT_INIT] = "OBJECT_INIT",
[FSCACHE_OBJECT_LOOKING_UP] = "OBJECT_LOOKING_UP",
[FSCACHE_OBJECT_CREATING] = "OBJECT_CREATING",
[FSCACHE_OBJECT_AVAILABLE] = "OBJECT_AVAILABLE",
[FSCACHE_OBJECT_ACTIVE] = "OBJECT_ACTIVE",
[FSCACHE_OBJECT_UPDATING] = "OBJECT_UPDATING",
[FSCACHE_OBJECT_DYING] = "OBJECT_DYING",
[FSCACHE_OBJECT_LC_DYING] = "OBJECT_LC_DYING",
[FSCACHE_OBJECT_ABORT_INIT] = "OBJECT_ABORT_INIT",
[FSCACHE_OBJECT_RELEASING] = "OBJECT_RELEASING",
[FSCACHE_OBJECT_RECYCLING] = "OBJECT_RECYCLING",
[FSCACHE_OBJECT_WITHDRAWING] = "OBJECT_WITHDRAWING",
[FSCACHE_OBJECT_DEAD] = "OBJECT_DEAD",
};
EXPORT_SYMBOL(fscache_object_states);
const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
[FSCACHE_OBJECT_INIT] = "INIT",
[FSCACHE_OBJECT_LOOKING_UP] = "LOOK",
[FSCACHE_OBJECT_CREATING] = "CRTN",
[FSCACHE_OBJECT_AVAILABLE] = "AVBL",
[FSCACHE_OBJECT_ACTIVE] = "ACTV",
[FSCACHE_OBJECT_UPDATING] = "UPDT",
[FSCACHE_OBJECT_DYING] = "DYNG",
[FSCACHE_OBJECT_LC_DYING] = "LCDY",
[FSCACHE_OBJECT_ABORT_INIT] = "ABTI",
[FSCACHE_OBJECT_RELEASING] = "RELS",
[FSCACHE_OBJECT_RECYCLING] = "RCYC",
[FSCACHE_OBJECT_WITHDRAWING] = "WTHD",
[FSCACHE_OBJECT_DEAD] = "DEAD",
};
static void fscache_object_slow_work_put_ref(struct slow_work *);
static int fscache_object_slow_work_get_ref(struct slow_work *);
static void fscache_object_slow_work_execute(struct slow_work *);
#ifdef CONFIG_SLOW_WORK_PROC
static void fscache_object_slow_work_desc(struct slow_work *, struct seq_file *);
#endif
static void fscache_initialise_object(struct fscache_object *);
static void fscache_lookup_object(struct fscache_object *);
static void fscache_object_available(struct fscache_object *);
static void fscache_release_object(struct fscache_object *);
static void fscache_withdraw_object(struct fscache_object *);
static void fscache_enqueue_dependents(struct fscache_object *);
static void fscache_dequeue_object(struct fscache_object *);
const struct slow_work_ops fscache_object_slow_work_ops = {
.owner = THIS_MODULE,
.get_ref = fscache_object_slow_work_get_ref,
.put_ref = fscache_object_slow_work_put_ref,
.execute = fscache_object_slow_work_execute,
#ifdef CONFIG_SLOW_WORK_PROC
.desc = fscache_object_slow_work_desc,
#endif
};
EXPORT_SYMBOL(fscache_object_slow_work_ops);
/*
* we need to notify the parent when an op completes that we had outstanding
* upon it
*/
static inline void fscache_done_parent_op(struct fscache_object *object)
{
struct fscache_object *parent = object->parent;
_enter("OBJ%x {OBJ%x,%x}",
object->debug_id, parent->debug_id, parent->n_ops);
spin_lock_nested(&parent->lock, 1);
parent->n_ops--;
parent->n_obj_ops--;
if (parent->n_ops == 0)
fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
spin_unlock(&parent->lock);
}
/*
* process events that have been sent to an object's state machine
* - initiates parent lookup
* - does object lookup
* - does object creation
* - does object recycling and retirement
* - does object withdrawal
*/
static void fscache_object_state_machine(struct fscache_object *object)
{
enum fscache_object_state new_state;
struct fscache_cookie *cookie;
ASSERT(object != NULL);
_enter("{OBJ%x,%s,%lx}",
object->debug_id, fscache_object_states[object->state],
object->events);
switch (object->state) {
/* wait for the parent object to become ready */
case FSCACHE_OBJECT_INIT:
object->event_mask =
ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
fscache_initialise_object(object);
goto done;
/* look up the object metadata on disk */
case FSCACHE_OBJECT_LOOKING_UP:
fscache_lookup_object(object);
goto lookup_transit;
/* create the object metadata on disk */
case FSCACHE_OBJECT_CREATING:
fscache_lookup_object(object);
goto lookup_transit;
/* handle an object becoming available; start pending
* operations and queue dependent operations for processing */
case FSCACHE_OBJECT_AVAILABLE:
fscache_object_available(object);
goto active_transit;
/* normal running state */
case FSCACHE_OBJECT_ACTIVE:
goto active_transit;
/* update the object metadata on disk */
case FSCACHE_OBJECT_UPDATING:
clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
fscache_stat(&fscache_n_updates_run);
fscache_stat(&fscache_n_cop_update_object);
object->cache->ops->update_object(object);
fscache_stat_d(&fscache_n_cop_update_object);
goto active_transit;
/* handle an object dying during lookup or creation */
case FSCACHE_OBJECT_LC_DYING:
object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
fscache_stat(&fscache_n_cop_lookup_complete);
object->cache->ops->lookup_complete(object);
fscache_stat_d(&fscache_n_cop_lookup_complete);
spin_lock(&object->lock);
object->state = FSCACHE_OBJECT_DYING;
cookie = object->cookie;
if (cookie) {
if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
&cookie->flags))
wake_up_bit(&cookie->flags,
FSCACHE_COOKIE_LOOKING_UP);
if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
&cookie->flags))
wake_up_bit(&cookie->flags,
FSCACHE_COOKIE_CREATING);
}
spin_unlock(&object->lock);
fscache_done_parent_op(object);
/* wait for completion of all active operations on this object
* and the death of all child objects of this object */
case FSCACHE_OBJECT_DYING:
dying:
clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
spin_lock(&object->lock);
_debug("dying OBJ%x {%d,%d}",
object->debug_id, object->n_ops, object->n_children);
if (object->n_ops == 0 && object->n_children == 0) {
object->event_mask &=
~(1 << FSCACHE_OBJECT_EV_CLEARED);
object->event_mask |=
(1 << FSCACHE_OBJECT_EV_WITHDRAW) |
(1 << FSCACHE_OBJECT_EV_RETIRE) |
(1 << FSCACHE_OBJECT_EV_RELEASE) |
(1 << FSCACHE_OBJECT_EV_ERROR);
} else {
object->event_mask &=
~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
(1 << FSCACHE_OBJECT_EV_RETIRE) |
(1 << FSCACHE_OBJECT_EV_RELEASE) |
(1 << FSCACHE_OBJECT_EV_ERROR));
object->event_mask |=
1 << FSCACHE_OBJECT_EV_CLEARED;
}
spin_unlock(&object->lock);
fscache_enqueue_dependents(object);
fscache_start_operations(object);
goto terminal_transit;
/* handle an abort during initialisation */
case FSCACHE_OBJECT_ABORT_INIT:
_debug("handle abort init %lx", object->events);
object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
spin_lock(&object->lock);
fscache_dequeue_object(object);
object->state = FSCACHE_OBJECT_DYING;
if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
&object->cookie->flags))
wake_up_bit(&object->cookie->flags,
FSCACHE_COOKIE_CREATING);
spin_unlock(&object->lock);
goto dying;
/* handle the netfs releasing an object and possibly marking it
* obsolete too */
case FSCACHE_OBJECT_RELEASING:
case FSCACHE_OBJECT_RECYCLING:
object->event_mask &=
~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
(1 << FSCACHE_OBJECT_EV_RETIRE) |
(1 << FSCACHE_OBJECT_EV_RELEASE) |
(1 << FSCACHE_OBJECT_EV_ERROR));
fscache_release_object(object);
spin_lock(&object->lock);
object->state = FSCACHE_OBJECT_DEAD;
spin_unlock(&object->lock);
fscache_stat(&fscache_n_object_dead);
goto terminal_transit;
/* handle the parent cache of this object being withdrawn from
* active service */
case FSCACHE_OBJECT_WITHDRAWING:
object->event_mask &=
~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
(1 << FSCACHE_OBJECT_EV_RETIRE) |
(1 << FSCACHE_OBJECT_EV_RELEASE) |
(1 << FSCACHE_OBJECT_EV_ERROR));
fscache_withdraw_object(object);
spin_lock(&object->lock);
object->state = FSCACHE_OBJECT_DEAD;
spin_unlock(&object->lock);
fscache_stat(&fscache_n_object_dead);
goto terminal_transit;
/* complain about the object being woken up once it is
* deceased */
case FSCACHE_OBJECT_DEAD:
printk(KERN_ERR "FS-Cache:"
" Unexpected event in dead state %lx\n",
object->events & object->event_mask);
BUG();
default:
printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
object->state);
BUG();
}
/* determine the transition from a lookup state */
lookup_transit:
switch (fls(object->events & object->event_mask) - 1) {
case FSCACHE_OBJECT_EV_WITHDRAW:
case FSCACHE_OBJECT_EV_RETIRE:
case FSCACHE_OBJECT_EV_RELEASE:
case FSCACHE_OBJECT_EV_ERROR:
new_state = FSCACHE_OBJECT_LC_DYING;
goto change_state;
case FSCACHE_OBJECT_EV_REQUEUE:
goto done;
case -1:
goto done; /* sleep until event */
default:
goto unsupported_event;
}
/* determine the transition from an active state */
active_transit:
switch (fls(object->events & object->event_mask) - 1) {
case FSCACHE_OBJECT_EV_WITHDRAW:
case FSCACHE_OBJECT_EV_RETIRE:
case FSCACHE_OBJECT_EV_RELEASE:
case FSCACHE_OBJECT_EV_ERROR:
new_state = FSCACHE_OBJECT_DYING;
goto change_state;
case FSCACHE_OBJECT_EV_UPDATE:
new_state = FSCACHE_OBJECT_UPDATING;
goto change_state;
case -1:
new_state = FSCACHE_OBJECT_ACTIVE;
goto change_state; /* sleep until event */
default:
goto unsupported_event;
}
/* determine the transition from a terminal state */
terminal_transit:
switch (fls(object->events & object->event_mask) - 1) {
case FSCACHE_OBJECT_EV_WITHDRAW:
new_state = FSCACHE_OBJECT_WITHDRAWING;
goto change_state;
case FSCACHE_OBJECT_EV_RETIRE:
new_state = FSCACHE_OBJECT_RECYCLING;
goto change_state;
case FSCACHE_OBJECT_EV_RELEASE:
new_state = FSCACHE_OBJECT_RELEASING;
goto change_state;
case FSCACHE_OBJECT_EV_ERROR:
new_state = FSCACHE_OBJECT_WITHDRAWING;
goto change_state;
case FSCACHE_OBJECT_EV_CLEARED:
new_state = FSCACHE_OBJECT_DYING;
goto change_state;
case -1:
goto done; /* sleep until event */
default:
goto unsupported_event;
}
change_state:
spin_lock(&object->lock);
object->state = new_state;
spin_unlock(&object->lock);
done:
_leave(" [->%s]", fscache_object_states[object->state]);
return;
unsupported_event:
printk(KERN_ERR "FS-Cache:"
" Unsupported event %lx [mask %lx] in state %s\n",
object->events, object->event_mask,
fscache_object_states[object->state]);
BUG();
}
/*
* execute an object
*/
static void fscache_object_slow_work_execute(struct slow_work *work)
{
struct fscache_object *object =
container_of(work, struct fscache_object, work);
unsigned long start;
_enter("{OBJ%x}", object->debug_id);
start = jiffies;
fscache_object_state_machine(object);
fscache_hist(fscache_objs_histogram, start);
if (object->events & object->event_mask)
fscache_enqueue_object(object);
clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
}
/*
* describe an object for slow-work debugging
*/
#ifdef CONFIG_SLOW_WORK_PROC
static void fscache_object_slow_work_desc(struct slow_work *work,
struct seq_file *m)
{
struct fscache_object *object =
container_of(work, struct fscache_object, work);
seq_printf(m, "FSC: OBJ%x: %s",
object->debug_id,
fscache_object_states_short[object->state]);
}
#endif
/*
* initialise an object
* - check the specified object's parent to see if we can make use of it
* immediately to do a creation
* - we may need to start the process of creating a parent and we need to wait
* for the parent's lookup and creation to complete if it's not there yet
* - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
* leaf-most cookies of the object and all its children
*/
static void fscache_initialise_object(struct fscache_object *object)
{
struct fscache_object *parent;
_enter("");
ASSERT(object->cookie != NULL);
ASSERT(object->cookie->parent != NULL);
ASSERT(list_empty(&object->work.link));
if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
(1 << FSCACHE_OBJECT_EV_RELEASE) |
(1 << FSCACHE_OBJECT_EV_RETIRE) |
(1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
_debug("abort init %lx", object->events);
spin_lock(&object->lock);
object->state = FSCACHE_OBJECT_ABORT_INIT;
spin_unlock(&object->lock);
return;
}
spin_lock(&object->cookie->lock);
spin_lock_nested(&object->cookie->parent->lock, 1);
parent = object->parent;
if (!parent) {
_debug("no parent");
set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
} else {
spin_lock(&object->lock);
spin_lock_nested(&parent->lock, 1);
_debug("parent %s", fscache_object_states[parent->state]);
if (parent->state >= FSCACHE_OBJECT_DYING) {
_debug("bad parent");
set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
} else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
_debug("wait");
/* we may get woken up in this state by child objects
* binding on to us, so we need to make sure we don't
* add ourself to the list multiple times */
if (list_empty(&object->dep_link)) {
fscache_stat(&fscache_n_cop_grab_object);
object->cache->ops->grab_object(object);
fscache_stat_d(&fscache_n_cop_grab_object);
list_add(&object->dep_link,
&parent->dependents);
/* fscache_acquire_non_index_cookie() uses this
* to wake the chain up */
if (parent->state == FSCACHE_OBJECT_INIT)
fscache_enqueue_object(parent);
}
} else {
_debug("go");
parent->n_ops++;
parent->n_obj_ops++;
object->lookup_jif = jiffies;
object->state = FSCACHE_OBJECT_LOOKING_UP;
set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
}
spin_unlock(&parent->lock);
spin_unlock(&object->lock);
}
spin_unlock(&object->cookie->parent->lock);
spin_unlock(&object->cookie->lock);
_leave("");
}
/*
* look an object up in the cache from which it was allocated
* - we hold an "access lock" on the parent object, so the parent object cannot
* be withdrawn by either party till we've finished
* - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
* leaf-most cookies of the object and all its children
*/
static void fscache_lookup_object(struct fscache_object *object)
{
struct fscache_cookie *cookie = object->cookie;
struct fscache_object *parent;
int ret;
_enter("");
parent = object->parent;
ASSERT(parent != NULL);
ASSERTCMP(parent->n_ops, >, 0);
ASSERTCMP(parent->n_obj_ops, >, 0);
/* make sure the parent is still available */
ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
if (parent->state >= FSCACHE_OBJECT_DYING ||
test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
_debug("unavailable");
set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
_leave("");
return;
}
_debug("LOOKUP \"%s/%s\" in \"%s\"",
parent->cookie->def->name, cookie->def->name,
object->cache->tag->name);
fscache_stat(&fscache_n_object_lookups);
fscache_stat(&fscache_n_cop_lookup_object);
ret = object->cache->ops->lookup_object(object);
fscache_stat_d(&fscache_n_cop_lookup_object);
if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
if (ret == -ETIMEDOUT) {
/* probably stuck behind another object, so move this one to
* the back of the queue */
fscache_stat(&fscache_n_object_lookups_timed_out);
set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
}
_leave("");
}
/**
* fscache_object_lookup_negative - Note negative cookie lookup
* @object: Object pointing to cookie to mark
*
* Note negative lookup, permitting those waiting to read data from an already
* existing backing object to continue as there's no data for them to read.
*/
void fscache_object_lookup_negative(struct fscache_object *object)
{
struct fscache_cookie *cookie = object->cookie;
_enter("{OBJ%x,%s}",
object->debug_id, fscache_object_states[object->state]);
spin_lock(&object->lock);
if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
fscache_stat(&fscache_n_object_lookups_negative);
/* transit here to allow write requests to begin stacking up
* and read requests to begin returning ENODATA */
object->state = FSCACHE_OBJECT_CREATING;
spin_unlock(&object->lock);
set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
_debug("wake up lookup %p", &cookie->flags);
smp_mb__before_clear_bit();
clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
smp_mb__after_clear_bit();
wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
} else {
ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
spin_unlock(&object->lock);
}
_leave("");
}
EXPORT_SYMBOL(fscache_object_lookup_negative);
/**
* fscache_obtained_object - Note successful object lookup or creation
* @object: Object pointing to cookie to mark
*
* Note successful lookup and/or creation, permitting those waiting to write
* data to a backing object to continue.
*
* Note that after calling this, an object's cookie may be relinquished by the
* netfs, and so must be accessed with object lock held.
*/
void fscache_obtained_object(struct fscache_object *object)
{
struct fscache_cookie *cookie = object->cookie;
_enter("{OBJ%x,%s}",
object->debug_id, fscache_object_states[object->state]);
/* if we were still looking up, then we must have a positive lookup
* result, in which case there may be data available */
spin_lock(&object->lock);
if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
fscache_stat(&fscache_n_object_lookups_positive);
clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
object->state = FSCACHE_OBJECT_AVAILABLE;
spin_unlock(&object->lock);
smp_mb__before_clear_bit();
clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
smp_mb__after_clear_bit();
wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
} else {
ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
fscache_stat(&fscache_n_object_created);
object->state = FSCACHE_OBJECT_AVAILABLE;
spin_unlock(&object->lock);
set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
smp_wmb();
}
if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
_leave("");
}
EXPORT_SYMBOL(fscache_obtained_object);
/*
* handle an object that has just become available
*/
static void fscache_object_available(struct fscache_object *object)
{
_enter("{OBJ%x}", object->debug_id);
spin_lock(&object->lock);
if (object->cookie &&
test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
fscache_done_parent_op(object);
if (object->n_in_progress == 0) {
if (object->n_ops > 0) {
ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
ASSERTIF(object->n_ops > object->n_obj_ops,
!list_empty(&object->pending_ops));
fscache_start_operations(object);
} else {
ASSERT(list_empty(&object->pending_ops));
}
}
spin_unlock(&object->lock);
fscache_stat(&fscache_n_cop_lookup_complete);
object->cache->ops->lookup_complete(object);
fscache_stat_d(&fscache_n_cop_lookup_complete);
fscache_enqueue_dependents(object);
fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
fscache_stat(&fscache_n_object_avail);
_leave("");
}
/*
* drop an object's attachments
*/
static void fscache_drop_object(struct fscache_object *object)
{
struct fscache_object *parent = object->parent;
struct fscache_cache *cache = object->cache;
_enter("{OBJ%x,%d}", object->debug_id, object->n_children);
ASSERTCMP(object->cookie, ==, NULL);
ASSERT(hlist_unhashed(&object->cookie_link));
spin_lock(&cache->object_list_lock);
list_del_init(&object->cache_link);
spin_unlock(&cache->object_list_lock);
fscache_stat(&fscache_n_cop_drop_object);
cache->ops->drop_object(object);
fscache_stat_d(&fscache_n_cop_drop_object);
if (parent) {
_debug("release parent OBJ%x {%d}",
parent->debug_id, parent->n_children);
spin_lock(&parent->lock);
parent->n_children--;
if (parent->n_children == 0)
fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
spin_unlock(&parent->lock);
object->parent = NULL;
}
/* this just shifts the object release to the slow work processor */
fscache_stat(&fscache_n_cop_put_object);
object->cache->ops->put_object(object);
fscache_stat_d(&fscache_n_cop_put_object);
_leave("");
}
/*
* release or recycle an object that the netfs has discarded
*/
static void fscache_release_object(struct fscache_object *object)
{
_enter("");
fscache_drop_object(object);
}
/*
* withdraw an object from active service
*/
static void fscache_withdraw_object(struct fscache_object *object)
{
struct fscache_cookie *cookie;
bool detached;
_enter("");
spin_lock(&object->lock);
cookie = object->cookie;
if (cookie) {
/* need to get the cookie lock before the object lock, starting
* from the object pointer */
atomic_inc(&cookie->usage);
spin_unlock(&object->lock);
detached = false;
spin_lock(&cookie->lock);
spin_lock(&object->lock);
if (object->cookie == cookie) {
hlist_del_init(&object->cookie_link);
object->cookie = NULL;
detached = true;
}
spin_unlock(&cookie->lock);
fscache_cookie_put(cookie);
if (detached)
fscache_cookie_put(cookie);
}
spin_unlock(&object->lock);
fscache_drop_object(object);
}
/*
* withdraw an object from active service at the behest of the cache
* - need break the links to a cached object cookie
* - called under two situations:
* (1) recycler decides to reclaim an in-use object
* (2) a cache is unmounted
* - have to take care as the cookie can be being relinquished by the netfs
* simultaneously
* - the object is pinned by the caller holding a refcount on it
*/
void fscache_withdrawing_object(struct fscache_cache *cache,
struct fscache_object *object)
{
bool enqueue = false;
_enter(",OBJ%x", object->debug_id);
spin_lock(&object->lock);
if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
object->state = FSCACHE_OBJECT_WITHDRAWING;
enqueue = true;
}
spin_unlock(&object->lock);
if (enqueue)
fscache_enqueue_object(object);
_leave("");
}
/*
* allow the slow work item processor to get a ref on an object
*/
static int fscache_object_slow_work_get_ref(struct slow_work *work)
{
struct fscache_object *object =
container_of(work, struct fscache_object, work);
int ret;
fscache_stat(&fscache_n_cop_grab_object);
ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
fscache_stat_d(&fscache_n_cop_grab_object);
return ret;
}
/*
* allow the slow work item processor to discard a ref on a work item
*/
static void fscache_object_slow_work_put_ref(struct slow_work *work)
{
struct fscache_object *object =
container_of(work, struct fscache_object, work);
fscache_stat(&fscache_n_cop_put_object);
object->cache->ops->put_object(object);
fscache_stat_d(&fscache_n_cop_put_object);
}
/*
* enqueue an object for metadata-type processing
*/
void fscache_enqueue_object(struct fscache_object *object)
{
_enter("{OBJ%x}", object->debug_id);
slow_work_enqueue(&object->work);
}
/*
* enqueue the dependents of an object for metadata-type processing
* - the caller must hold the object's lock
* - this may cause an already locked object to wind up being processed again
*/
static void fscache_enqueue_dependents(struct fscache_object *object)
{
struct fscache_object *dep;
_enter("{OBJ%x}", object->debug_id);
if (list_empty(&object->dependents))
return;
spin_lock(&object->lock);
while (!list_empty(&object->dependents)) {
dep = list_entry(object->dependents.next,
struct fscache_object, dep_link);
list_del_init(&dep->dep_link);
/* sort onto appropriate lists */
fscache_enqueue_object(dep);
fscache_stat(&fscache_n_cop_put_object);
dep->cache->ops->put_object(dep);
fscache_stat_d(&fscache_n_cop_put_object);
if (!list_empty(&object->dependents))
cond_resched_lock(&object->lock);
}
spin_unlock(&object->lock);
}
/*
* remove an object from whatever queue it's waiting on
* - the caller must hold object->lock
*/
void fscache_dequeue_object(struct fscache_object *object)
{
_enter("{OBJ%x}", object->debug_id);
if (!list_empty(&object->dep_link)) {
spin_lock(&object->parent->lock);
list_del_init(&object->dep_link);
spin_unlock(&object->parent->lock);
}
_leave("");
}
/**
* fscache_check_aux - Ask the netfs whether an object on disk is still valid
* @object: The object to ask about
* @data: The auxiliary data for the object
* @datalen: The size of the auxiliary data
*
* This function consults the netfs about the coherency state of an object
*/
enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
const void *data, uint16_t datalen)
{
enum fscache_checkaux result;
if (!object->cookie->def->check_aux) {
fscache_stat(&fscache_n_checkaux_none);
return FSCACHE_CHECKAUX_OKAY;
}
result = object->cookie->def->check_aux(object->cookie->netfs_data,
data, datalen);
switch (result) {
/* entry okay as is */
case FSCACHE_CHECKAUX_OKAY:
fscache_stat(&fscache_n_checkaux_okay);
break;
/* entry requires update */
case FSCACHE_CHECKAUX_NEEDS_UPDATE:
fscache_stat(&fscache_n_checkaux_update);
break;
/* entry requires deletion */
case FSCACHE_CHECKAUX_OBSOLETE:
fscache_stat(&fscache_n_checkaux_obsolete);
break;
default:
BUG();
}
return result;
}
EXPORT_SYMBOL(fscache_check_aux);