From e3d4d28b1c8cc7c26536a50b43d86ccd39878550 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 19 Nov 2009 18:11:32 +0000 Subject: [PATCH] FS-Cache: Handle read request vs lookup, creation or other cache failure FS-Cache doesn't correctly handle the netfs requesting a read from the cache on an object that failed or was withdrawn by the cache. A trace similar to the following might be seen: CacheFiles: Lookup failed error -105 [exe ] unexpected submission OP165afe [OBJ6cac OBJECT_LC_DYING] [exe ] objstate=OBJECT_LC_DYING [OBJECT_LC_DYING] [exe ] objflags=0 [exe ] objevent=9 [fffffffffffffffb] [exe ] ops=0 inp=0 exc=0 Pid: 6970, comm: exe Not tainted 2.6.32-rc6-cachefs #50 Call Trace: [] fscache_submit_op+0x3ff/0x45a [fscache] [] __fscache_read_or_alloc_pages+0x187/0x3c4 [fscache] [] ? nfs_readpage_from_fscache_complete+0x0/0x66 [nfs] [] __nfs_readpages_from_fscache+0x7e/0x176 [nfs] [] ? __alloc_pages_nodemask+0x11c/0x5cf [] nfs_readpages+0x114/0x1d7 [nfs] [] __do_page_cache_readahead+0x15f/0x1ec [] ? __do_page_cache_readahead+0x73/0x1ec [] ra_submit+0x1c/0x20 [] ondemand_readahead+0x227/0x23a [] page_cache_sync_readahead+0x17/0x19 [] generic_file_aio_read+0x236/0x5a0 [] nfs_file_read+0xe4/0xf3 [nfs] [] do_sync_read+0xe3/0x120 [] ? _spin_unlock_irq+0x2b/0x31 [] ? autoremove_wake_function+0x0/0x34 [] ? selinux_file_permission+0x5d/0x10f [] ? thread_return+0x3e/0x101 [] ? security_file_permission+0x11/0x13 [] vfs_read+0xaa/0x16f [] ? trace_hardirqs_on_caller+0x10c/0x130 [] sys_read+0x45/0x6c [] system_call_fastpath+0x16/0x1b The object state might also be OBJECT_DYING or OBJECT_WITHDRAWING. This should be handled by simply rejecting the new operation with ENOBUFS. There's no need to log an error for it. Events of this type now appear in the stats file under Ops:rej. Signed-off-by: David Howells --- Documentation/filesystems/caching/fscache.txt | 1 + fs/fscache/internal.h | 1 + fs/fscache/operation.c | 5 +++++ fs/fscache/stats.c | 6 ++++-- 4 files changed, 11 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt index 9cf2cfbc81c..057a3c71d52 100644 --- a/Documentation/filesystems/caching/fscache.txt +++ b/Documentation/filesystems/caching/fscache.txt @@ -276,6 +276,7 @@ proc files. run=N Number of times async ops given CPU time enq=N Number of times async ops queued for processing can=N Number of async ops cancelled + rej=N Number of async ops rejected due to object lookup/create failure dfr=N Number of async ops queued for deferred release rel=N Number of async ops released gc=N Number of deferred-release async ops garbage collected diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index ba1853fa1ff..a0769872b19 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -143,6 +143,7 @@ extern atomic_t fscache_n_op_deferred_release; extern atomic_t fscache_n_op_release; extern atomic_t fscache_n_op_gc; extern atomic_t fscache_n_op_cancelled; +extern atomic_t fscache_n_op_rejected; extern atomic_t fscache_n_attr_changed; extern atomic_t fscache_n_attr_changed_ok; diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c index 296492efb81..313e79a1426 100644 --- a/fs/fscache/operation.c +++ b/fs/fscache/operation.c @@ -232,6 +232,11 @@ int fscache_submit_op(struct fscache_object *object, list_add_tail(&op->pend_link, &object->pending_ops); fscache_stat(&fscache_n_op_pend); ret = 0; + } else if (object->state == FSCACHE_OBJECT_DYING || + object->state == FSCACHE_OBJECT_LC_DYING || + object->state == FSCACHE_OBJECT_WITHDRAWING) { + fscache_stat(&fscache_n_op_rejected); + ret = -ENOBUFS; } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) { fscache_report_unexpected_submission(object, op, ostate); ASSERT(!fscache_object_is_active(object)); diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c index 1d53ea68409..045ba396dbf 100644 --- a/fs/fscache/stats.c +++ b/fs/fscache/stats.c @@ -26,6 +26,7 @@ atomic_t fscache_n_op_deferred_release; atomic_t fscache_n_op_release; atomic_t fscache_n_op_gc; atomic_t fscache_n_op_cancelled; +atomic_t fscache_n_op_rejected; atomic_t fscache_n_attr_changed; atomic_t fscache_n_attr_changed_ok; @@ -210,11 +211,12 @@ static int fscache_stats_show(struct seq_file *m, void *v) atomic_read(&fscache_n_store_radix_deletes), atomic_read(&fscache_n_store_pages_over_limit)); - seq_printf(m, "Ops : pend=%u run=%u enq=%u can=%u\n", + seq_printf(m, "Ops : pend=%u run=%u enq=%u can=%u rej=%u\n", atomic_read(&fscache_n_op_pend), atomic_read(&fscache_n_op_run), atomic_read(&fscache_n_op_enqueue), - atomic_read(&fscache_n_op_cancelled)); + atomic_read(&fscache_n_op_cancelled), + atomic_read(&fscache_n_op_rejected)); seq_printf(m, "Ops : dfr=%u rel=%u gc=%u\n", atomic_read(&fscache_n_op_deferred_release), atomic_read(&fscache_n_op_release),