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authorDavid Howells <dhowells@redhat.com>2009-11-19 18:12:05 +0000
committerDavid Howells <dhowells@redhat.com>2009-11-19 18:12:05 +0000
commitfee096deb4f33897937b974cb2c5168bab7935be (patch)
treec86e5ed5b3435ff0f0266f343b19f8cc7be63340 /fs/cachefiles/interface.c
parentd0e27b7808dc667f3015be0b6888f6d680e222c8 (diff)
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>
Diffstat (limited to 'fs/cachefiles/interface.c')
-rw-r--r--fs/cachefiles/interface.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 8e67abf0598..9d3c426044a 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -114,8 +114,9 @@ nomem_lookup_data:
/*
* attempt to look up the nominated node in this cache
+ * - return -ETIMEDOUT to be scheduled again
*/
-static void cachefiles_lookup_object(struct fscache_object *_object)
+static int cachefiles_lookup_object(struct fscache_object *_object)
{
struct cachefiles_lookup_data *lookup_data;
struct cachefiles_object *parent, *object;
@@ -145,13 +146,14 @@ static void cachefiles_lookup_object(struct fscache_object *_object)
object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
cachefiles_attr_changed(&object->fscache);
- if (ret < 0) {
+ if (ret < 0 && ret != -ETIMEDOUT) {
printk(KERN_WARNING "CacheFiles: Lookup failed error %d\n",
ret);
fscache_object_lookup_error(&object->fscache);
}
_leave(" [%d]", ret);
+ return ret;
}
/*