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authorDavid Howells <dhowells@redhat.com>2009-11-19 21:11:32 +0300
committerDavid Howells <dhowells@redhat.com>2009-11-19 21:11:32 +0300
commite3d4d28b1c8cc7c26536a50b43d86ccd39878550 (patch)
tree23f6dacd5ffdf6c6d01c411517855a41405381b9 /Documentation/filesystems/caching
parent285e728b0ac55b53a673114096168d6f74930167 (diff)
downloadlinux-e3d4d28b1c8cc7c26536a50b43d86ccd39878550.tar.xz
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FS-Cache doesn't correctly handle the netfs requesting a read from the cache on an object that failed or was withdrawn by the cache.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: [<ffffffffa0076477>] fscache_submit_op+0x3ff/0x45a [fscache] [<ffffffffa0077997>] __fscache_read_or_alloc_pages+0x187/0x3c4 [fscache] [<ffffffffa00b6480>] ? nfs_readpage_from_fscache_complete+0x0/0x66 [nfs] [<ffffffffa00b6388>] __nfs_readpages_from_fscache+0x7e/0x176 [nfs] [<ffffffff8108e483>] ? __alloc_pages_nodemask+0x11c/0x5cf [<ffffffffa009d796>] nfs_readpages+0x114/0x1d7 [nfs] [<ffffffff81090314>] __do_page_cache_readahead+0x15f/0x1ec [<ffffffff81090228>] ? __do_page_cache_readahead+0x73/0x1ec [<ffffffff810903bd>] ra_submit+0x1c/0x20 [<ffffffff810906bb>] ondemand_readahead+0x227/0x23a [<ffffffff81090762>] page_cache_sync_readahead+0x17/0x19 [<ffffffff8108a99e>] generic_file_aio_read+0x236/0x5a0 [<ffffffffa00937bd>] nfs_file_read+0xe4/0xf3 [nfs] [<ffffffff810b2fa2>] do_sync_read+0xe3/0x120 [<ffffffff81354cc3>] ? _spin_unlock_irq+0x2b/0x31 [<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34 [<ffffffff811848e5>] ? selinux_file_permission+0x5d/0x10f [<ffffffff81352bdb>] ? thread_return+0x3e/0x101 [<ffffffff8117d7b0>] ? security_file_permission+0x11/0x13 [<ffffffff810b3b06>] vfs_read+0xaa/0x16f [<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130 [<ffffffff810b3c84>] sys_read+0x45/0x6c [<ffffffff8100ae2b>] 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 <dhowells@redhat.com>
Diffstat (limited to 'Documentation/filesystems/caching')
-rw-r--r--Documentation/filesystems/caching/fscache.txt1
1 files changed, 1 insertions, 0 deletions
diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 9cf2cfbc81c9..057a3c71d524 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