I'm not sure why, but the hlist for each entry iterators were conceived
list_for_each_entry(pos, head, member)
The hlist ones were greedy and wanted an extra parameter:
hlist_for_each_entry(tpos, pos, head, member)
Why did they need an extra pos parameter? I'm not quite sure. Not only
they don't really need it, it also prevents the iterator from looking
exactly like the list iterator, which is unfortunate.
Besides the semantic patch, there was some manual work required:
- Fix up the actual hlist iterators in linux/list.h
- Fix up the declaration of other iterators based on the hlist ones.
- A very small amount of places were using the 'node' parameter, this
was modified to use 'obj->member' instead.
- Coccinelle didn't handle the hlist_for_each_entry_safe iterator
properly, so those had to be fixed up manually.
The semantic patch which is mostly the work of Peter Senna Tschudin is here:
@@
iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host;
type T;
expression a,c,d,e;
identifier b;
statement S;
@@
-T b;
<+... when != b
(
hlist_for_each_entry(a,
- b,
c, d) S
|
hlist_for_each_entry_continue(a,
- b,
c) S
|
hlist_for_each_entry_from(a,
- b,
c) S
|
hlist_for_each_entry_rcu(a,
- b,
c, d) S
|
hlist_for_each_entry_rcu_bh(a,
- b,
c, d) S
|
hlist_for_each_entry_continue_rcu_bh(a,
- b,
c) S
|
for_each_busy_worker(a, c,
- b,
d) S
|
ax25_uid_for_each(a,
- b,
c) S
|
ax25_for_each(a,
- b,
c) S
|
inet_bind_bucket_for_each(a,
- b,
c) S
|
sctp_for_each_hentry(a,
- b,
c) S
|
sk_for_each(a,
- b,
c) S
|
sk_for_each_rcu(a,
- b,
c) S
|
sk_for_each_from
-(a, b)
+(a)
S
+ sk_for_each_from(a) S
|
sk_for_each_safe(a,
- b,
c, d) S
|
sk_for_each_bound(a,
- b,
c) S
|
hlist_for_each_entry_safe(a,
- b,
c, d, e) S
|
hlist_for_each_entry_continue_rcu(a,
- b,
c) S
|
nr_neigh_for_each(a,
- b,
c) S
|
nr_neigh_for_each_safe(a,
- b,
c, d) S
|
nr_node_for_each(a,
- b,
c) S
|
nr_node_for_each_safe(a,
- b,
c, d) S
|
- for_each_gfn_sp(a, c, d, b) S
+ for_each_gfn_sp(a, c, d) S
|
- for_each_gfn_indirect_valid_sp(a, c, d, b) S
+ for_each_gfn_indirect_valid_sp(a, c, d) S
|
for_each_host(a,
- b,
c) S
|
for_each_host_safe(a,
- b,
c, d) S
|
for_each_mesh_entry(a,
- b,
c, d) S
)
...+>
[akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c]
[akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c]
[akpm@linux-foundation.org: checkpatch fixes]
[akpm@linux-foundation.org: fix warnings]
[akpm@linux-foudnation.org: redo intrusive kvm changes]
Tested-by: Peter Senna Tschudin <peter.senna@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mark as cancelled an operation that is in progress rather than pending at the
time it is cancelled, and call fscache_complete_op() to cancel an operation so
that blocked ops can be started.
Signed-off-by: David Howells <dhowells@redhat.com>
In fscache_write_op(), if the object is determined to have become inactive or
to have lost its cookie, we don't move the operation state from in-progress,
and so an assertion in fscache_put_operation() fails with an assertion (see
below).
Instrumenting fscache_op_work_func() indicates that it called
fscache_write_op() before calling fscache_put_operation() - where the assertion
failed. The assertion at line 433 indicates that the operation state is
IN_PROGRESS rather than being COMPLETE or CANCELLED.
Instrumenting fscache_write_op() showed that it was being called on an object
that had had its cookie removed and that this was due to relinquishment of the
cookie by the netfs. At this point fscache no longer has access to the pages
of netfs data that were requested to be written, and so simply cancelling the
operation is the thing to do.
FS-Cache: Assertion failed
3 == 5 is false
------------[ cut here ]------------
kernel BUG at fs/fscache/operation.c:433!
invalid opcode: 0000 [#1] SMP
Modules linked in: cachefiles(F) nfsv4(F) nfsv3(F) nfsv2(F) nfs(F) fscache(F) auth_rpcgss(F) nfs_acl(F) lockd(F) sunrpc(F)
CPU 0
Pid: 1035, comm: kworker/u:3 Tainted: GF 3.7.0-rc8-fsdevel+ #411 /DG965RY
RIP: 0010:[<ffffffffa007db22>] [<ffffffffa007db22>] fscache_put_operation+0x11a/0x2ed [fscache]
RSP: 0018:ffff88003e32bcf8 EFLAGS: 00010296
RAX: 000000000000000f RBX: ffff88001818eb78 RCX: ffffffff6c102000
RDX: ffffffff8102d1ad RSI: ffffffff6c102000 RDI: ffffffff8102d1d6
RBP: ffff88003e32bd18 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffa00811da
R13: 0000000000000001 R14: 0000000100625d26 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88003bc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fff7dd31c68 CR3: 000000003d730000 CR4: 00000000000007f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kworker/u:3 (pid: 1035, threadinfo ffff88003e32a000, task ffff88003bb38080)
Stack:
ffffffff8102d1ad ffff88001818eb78 ffffffffa00811da 0000000000000001
ffff88003e32bd48 ffffffffa007f0ad ffff88001818eb78 ffffffff819583c0
ffff88003df24e00 ffff88003882c3e0 ffff88003e32bde8 ffffffff81042de0
Call Trace:
[<ffffffff8102d1ad>] ? vprintk_emit+0x3c6/0x41a
[<ffffffffa00811da>] ? __fscache_read_or_alloc_pages+0x4bc/0x4bc [fscache]
[<ffffffffa007f0ad>] fscache_op_work_func+0xec/0x123 [fscache]
[<ffffffff81042de0>] process_one_work+0x21c/0x3b0
[<ffffffff81042d82>] ? process_one_work+0x1be/0x3b0
[<ffffffffa007efc1>] ? fscache_operation_gc+0x23e/0x23e [fscache]
[<ffffffff8104332e>] worker_thread+0x202/0x2df
[<ffffffff8104312c>] ? rescuer_thread+0x18e/0x18e
[<ffffffff81047c1c>] kthread+0xd0/0xd8
[<ffffffff81421bfa>] ? _raw_spin_unlock_irq+0x29/0x3e
[<ffffffff81047b4c>] ? __init_kthread_worker+0x55/0x55
[<ffffffff814227ec>] ret_from_fork+0x7c/0xb0
[<ffffffff81047b4c>] ? __init_kthread_worker+0x55/0x55
Signed-off-by: David Howells <dhowells@redhat.com>
Add a missing transition to the FS-Cache object state machine to handle an
invalidation event occuring between the back end completing the object lookup
by calling fscache_obtained_object() (which moves to state OBJECT_AVAILABLE)
and the backend returning to fscache_lookup_object() and thence to
fscache_object_state_machine() which then does a goto lookup_transit to handle
the transition - but lookup_transit doesn't handle EV_INVALIDATE.
Without this, the following BUG can be logged:
FS-Cache: Unsupported event 2 [5/f7] in state OBJECT_AVAILABLE
------------[ cut here ]------------
kernel BUG at fs/fscache/object.c:357!
Where event 2 is EV_INVALIDATE.
Signed-off-by: David Howells <dhowells@redhat.com>
nfs_migrate_page() does not wait for FS-Cache to finish with a page, probably
leading to the following bad-page-state:
BUG: Bad page state in process python-bin pfn:17d39b
page:ffffea00053649e8 flags:004000000000100c count:0 mapcount:0 mapping:(null)
index:38686 (Tainted: G B ---------------- )
Pid: 31053, comm: python-bin Tainted: G B ----------------
2.6.32-71.24.1.el6.x86_64 #1
Call Trace:
[<ffffffff8111bfe7>] bad_page+0x107/0x160
[<ffffffff8111ee69>] free_hot_cold_page+0x1c9/0x220
[<ffffffff8111ef19>] __pagevec_free+0x59/0xb0
[<ffffffff8104b988>] ? flush_tlb_others_ipi+0x128/0x130
[<ffffffff8112230c>] release_pages+0x21c/0x250
[<ffffffff8115b92a>] ? remove_migration_pte+0x28a/0x2b0
[<ffffffff8115f3f8>] ? mem_cgroup_get_reclaim_stat_from_page+0x18/0x70
[<ffffffff81122687>] ____pagevec_lru_add+0x167/0x180
[<ffffffff811226f8>] __lru_cache_add+0x58/0x70
[<ffffffff81122731>] lru_cache_add_lru+0x21/0x40
[<ffffffff81123f49>] putback_lru_page+0x69/0x100
[<ffffffff8115c0bd>] migrate_pages+0x13d/0x5d0
[<ffffffff81122687>] ? ____pagevec_lru_add+0x167/0x180
[<ffffffff81152ab0>] ? compaction_alloc+0x0/0x370
[<ffffffff8115255c>] compact_zone+0x4cc/0x600
[<ffffffff8111cfac>] ? get_page_from_freelist+0x15c/0x820
[<ffffffff810672f4>] ? check_preempt_wakeup+0x1c4/0x3c0
[<ffffffff8115290e>] compact_zone_order+0x7e/0xb0
[<ffffffff81152a49>] try_to_compact_pages+0x109/0x170
[<ffffffff8111e94d>] __alloc_pages_nodemask+0x5ed/0x850
[<ffffffff814c9136>] ? thread_return+0x4e/0x778
[<ffffffff81150d43>] alloc_pages_vma+0x93/0x150
[<ffffffff81167ea5>] do_huge_pmd_anonymous_page+0x135/0x340
[<ffffffff814cb6f6>] ? rwsem_down_read_failed+0x26/0x30
[<ffffffff81136755>] handle_mm_fault+0x245/0x2b0
[<ffffffff814ce383>] do_page_fault+0x123/0x3a0
[<ffffffff814cbdf5>] page_fault+0x25/0x30
nfs_migrate_page() calls nfs_fscache_release_page() which doesn't actually wait
- even if __GFP_WAIT is set. The reason that doesn't wait is that
fscache_maybe_release_page() might deadlock the allocator as the work threads
writing to the cache may all end up sleeping on memory allocation.
However, I wonder if that is actually a problem. There are a number of things
I can do to deal with this:
(1) Make nfs_migrate_page() wait.
(2) Make fscache_maybe_release_page() honour the __GFP_WAIT flag.
(3) Set a timeout around the wait.
(4) Make nfs_migrate_page() return an error if the page is still busy.
For the moment, I'll select (2) and (4).
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
The function to submit an exclusive op (fscache_submit_exclusive_op()) can BUG
if there's been an I/O error because it may see the parent cache object in an
unexpected state. It should only BUG if there hasn't been an I/O error.
In this case the problem was produced by remounting the cache partition to be
R/O. The EROFS state was detected and the cache was aborted, but not
everything handled the aborting correctly.
SysRq : Emergency Remount R/O
EXT4-fs (sda6): re-mounted. Opts: (null)
Emergency Remount complete
CacheFiles: I/O Error: Failed to update xattr with error -30
FS-Cache: Cache cachefiles stopped due to I/O error
------------[ cut here ]------------
kernel BUG at fs/fscache/operation.c:128!
invalid opcode: 0000 [#1] SMP
CPU 0
Modules linked in: cachefiles nfs fscache auth_rpcgss nfs_acl lockd sunrpc
Pid: 6612, comm: kworker/u:2 Not tainted 3.1.0-rc8-fsdevel+ #1093 /DG965RY
RIP: 0010:[<ffffffffa00739c0>] [<ffffffffa00739c0>] fscache_submit_exclusive_op+0x2ad/0x2c2 [fscache]
RSP: 0018:ffff880000853d40 EFLAGS: 00010206
RAX: ffff880038ac72a8 RBX: ffff8800181f2260 RCX: ffffffff81f2b2b0
RDX: 0000000000000001 RSI: ffffffff8179a478 RDI: ffff8800181f2280
RBP: ffff880000853d60 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff880038ac7268
R13: ffff8800181f2280 R14: ffff88003a359190 R15: 000000010122b162
FS: 0000000000000000(0000) GS:ffff88003bc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000034cc4a77f0 CR3: 0000000010e96000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kworker/u:2 (pid: 6612, threadinfo ffff880000852000, task ffff880014c3c040)
Stack:
ffff8800181f2260 ffff8800181f2310 ffff880038ac7268 ffff8800181f2260
ffff880000853dc0 ffffffffa0072375 ffff880037ecfe00 ffff88003a359198
ffff880000853dc0 0000000000000246 0000000000000000 ffff88000a91d308
Call Trace:
[<ffffffffa0072375>] fscache_object_work_func+0x792/0xe65 [fscache]
[<ffffffff81047e44>] process_one_work+0x1eb/0x37f
[<ffffffff81047de6>] ? process_one_work+0x18d/0x37f
[<ffffffffa0071be3>] ? fscache_enqueue_dependents+0xd8/0xd8 [fscache]
[<ffffffff810482e4>] worker_thread+0x15a/0x21a
[<ffffffff8104818a>] ? rescuer_thread+0x188/0x188
[<ffffffff8104bf96>] kthread+0x7f/0x87
[<ffffffff813ad6f4>] kernel_thread_helper+0x4/0x10
[<ffffffff81026b98>] ? finish_task_switch+0x45/0xc0
[<ffffffff813abd1d>] ? retint_restore_args+0xe/0xe
[<ffffffff8104bf17>] ? __init_kthread_worker+0x53/0x53
[<ffffffff813ad6f0>] ? gs_change+0xb/0xb
Signed-off-by: David Howells <dhowells@redhat.com>
Limit the number of I/O error reports for a cache to 1 to prevent massive
amounts of noise. After the first I/O error the cache is taken off line
automatically, so must be restarted to resume caching.
Signed-off-by: David Howells <dhowells@redhat.com>
Don't mask off the object event mask when printing it. That way it can be seen
if threre are bits set that shouldn't be.
Signed-off-by: David Howells <dhowells@redhat.com>
Initialise the object event mask with the calculated mask rather than unmasking
undefined events also.
Signed-off-by: David Howells <dhowells@redhat.com>
Provide a proper invalidation method rather than relying on the netfs retiring
the cookie it has and getting a new one. The problem with this is that isn't
easy for the netfs to make sure that it has completed/cancelled all its
outstanding storage and retrieval operations on the cookie it is retiring.
Instead, have the cache provide an invalidation method that will cancel or wait
for all currently outstanding operations before invalidating the cache, and
will cause new operations to queue up behind that. Whilst invalidation is in
progress, some requests will be rejected until the cache can stack a barrier on
the operation queue to cause new operations to be deferred behind it.
Signed-off-by: David Howells <dhowells@redhat.com>
Fix the state management of internal fscache operations and the accounting of
what operations are in what states.
This is done by:
(1) Give struct fscache_operation a enum variable that directly represents the
state it's currently in, rather than spreading this knowledge over a bunch
of flags, who's processing the operation at the moment and whether it is
queued or not.
This makes it easier to write assertions to check the state at various
points and to prevent invalid state transitions.
(2) Add an 'operation complete' state and supply a function to indicate the
completion of an operation (fscache_op_complete()) and make things call
it. The final call to fscache_put_operation() can then check that an op
in the appropriate state (complete or cancelled).
(3) Adjust the use of object->n_ops, ->n_in_progress, ->n_exclusive to better
govern the state of an object:
(a) The ->n_ops is now the number of extant operations on the object
and is now decremented by fscache_put_operation() only.
(b) The ->n_in_progress is simply the number of objects that have been
taken off of the object's pending queue for the purposes of being
run. This is decremented by fscache_op_complete() only.
(c) The ->n_exclusive is the number of exclusive ops that have been
submitted and queued or are in progress. It is decremented by
fscache_op_complete() and by fscache_cancel_op().
fscache_put_operation() and fscache_operation_gc() now no longer try to
clean up ->n_exclusive and ->n_in_progress. That was leading to double
decrements against fscache_cancel_op().
fscache_cancel_op() now no longer decrements ->n_ops. That was leading to
double decrements against fscache_put_operation().
fscache_submit_exclusive_op() now decides whether it has to queue an op
based on ->n_in_progress being > 0 rather than ->n_ops > 0 as the latter
will persist in being true even after all preceding operations have been
cancelled or completed. Furthermore, if an object is active and there are
runnable ops against it, there must be at least one op running.
(4) Add a remaining-pages counter (n_pages) to struct fscache_retrieval and
provide a function to record completion of the pages as they complete.
When n_pages reaches 0, the operation is deemed to be complete and
fscache_op_complete() is called.
Add calls to fscache_retrieval_complete() anywhere we've finished with a
page we've been given to read or allocate for. This includes places where
we just return pages to the netfs for reading from the server and where
accessing the cache fails and we discard the proposed netfs page.
The bugs in the unfixed state management manifest themselves as oopses like the
following where the operation completion gets out of sync with return of the
cookie by the netfs. This is possible because the cache unlocks and returns
all the netfs pages before recording its completion - which means that there's
nothing to stop the netfs discarding them and returning the cookie.
FS-Cache: Cookie 'NFS.fh' still has outstanding reads
------------[ cut here ]------------
kernel BUG at fs/fscache/cookie.c:519!
invalid opcode: 0000 [#1] SMP
CPU 1
Modules linked in: cachefiles nfs fscache auth_rpcgss nfs_acl lockd sunrpc
Pid: 400, comm: kswapd0 Not tainted 3.1.0-rc7-fsdevel+ #1090 /DG965RY
RIP: 0010:[<ffffffffa007050a>] [<ffffffffa007050a>] __fscache_relinquish_cookie+0x170/0x343 [fscache]
RSP: 0018:ffff8800368cfb00 EFLAGS: 00010282
RAX: 000000000000003c RBX: ffff880023cc8790 RCX: 0000000000000000
RDX: 0000000000002f2e RSI: 0000000000000001 RDI: ffffffff813ab86c
RBP: ffff8800368cfb50 R08: 0000000000000002 R09: 0000000000000000
R10: ffff88003a1b7890 R11: ffff88001df6e488 R12: ffff880023d8ed98
R13: ffff880023cc8798 R14: 0000000000000004 R15: ffff88003b8bf370
FS: 0000000000000000(0000) GS:ffff88003bd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000000008ba008 CR3: 0000000023d93000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kswapd0 (pid: 400, threadinfo ffff8800368ce000, task ffff88003b8bf040)
Stack:
ffff88003b8bf040 ffff88001df6e528 ffff88001df6e528 ffffffffa00b46b0
ffff88003b8bf040 ffff88001df6e488 ffff88001df6e620 ffffffffa00b46b0
ffff88001ebd04c8 0000000000000004 ffff8800368cfb70 ffffffffa00b2c91
Call Trace:
[<ffffffffa00b2c91>] nfs_fscache_release_inode_cookie+0x3b/0x47 [nfs]
[<ffffffffa008f25f>] nfs_clear_inode+0x3c/0x41 [nfs]
[<ffffffffa0090df1>] nfs4_evict_inode+0x2f/0x33 [nfs]
[<ffffffff810d8d47>] evict+0xa1/0x15c
[<ffffffff810d8e2e>] dispose_list+0x2c/0x38
[<ffffffff810d9ebd>] prune_icache_sb+0x28c/0x29b
[<ffffffff810c56b7>] prune_super+0xd5/0x140
[<ffffffff8109b615>] shrink_slab+0x102/0x1ab
[<ffffffff8109d690>] balance_pgdat+0x2f2/0x595
[<ffffffff8103e009>] ? process_timeout+0xb/0xb
[<ffffffff8109dba3>] kswapd+0x270/0x289
[<ffffffff8104c5ea>] ? __init_waitqueue_head+0x46/0x46
[<ffffffff8109d933>] ? balance_pgdat+0x595/0x595
[<ffffffff8104bf7a>] kthread+0x7f/0x87
[<ffffffff813ad6b4>] kernel_thread_helper+0x4/0x10
[<ffffffff81026b98>] ? finish_task_switch+0x45/0xc0
[<ffffffff813abcdd>] ? retint_restore_args+0xe/0xe
[<ffffffff8104befb>] ? __init_kthread_worker+0x53/0x53
[<ffffffff813ad6b0>] ? gs_change+0xb/0xb
Signed-off-by: David Howells <dhowells@redhat.com>
Make fscache_relinquish_cookie() log a warning and wait if there are any
outstanding reads left on the cookie it was given.
Signed-off-by: David Howells <dhowells@redhat.com>
Check that the netfs isn't trying to relinquish a cookie that still has read
operations in progress upon it. If there are, then give log a warning and BUG.
Signed-off-by: David Howells <dhowells@redhat.com>
Downgrade the requirements passed to the allocator in the gfp flags parameter.
FS-Cache/CacheFiles can handle OOM conditions simply by aborting the attempt to
store an object or a page in the cache.
Signed-off-by: David Howells <dhowells@redhat.com>
Under some circumstances CacheFiles defers the marking of pages with PG_fscache
so that it can take advantage of pagevecs to reduce the number of calls to
fscache_mark_pages_cached() and the netfs's hook to keep track of this.
There are, however, two problems with this:
(1) It can lead to the PG_fscache mark being applied _after_ the page is set
PG_uptodate and unlocked (by the call to fscache_end_io()).
(2) CacheFiles's ref on the page is dropped immediately following
fscache_end_io() - and so may not still be held when the mark is applied.
This can lead to the page being passed back to the allocator before the
mark is applied.
Fix this by, where appropriate, marking the page before calling
fscache_end_io() and releasing the page. This means that we can't take
advantage of pagevecs and have to make a separate call for each page to the
marking routines.
The symptoms of this are Bad Page state errors cropping up under memory
pressure, for example:
BUG: Bad page state in process tar pfn:002da
page:ffffea0000009fb0 count:0 mapcount:0 mapping: (null) index:0x1447
page flags: 0x1000(private_2)
Pid: 4574, comm: tar Tainted: G W 3.1.0-rc4-fsdevel+ #1064
Call Trace:
[<ffffffff8109583c>] ? dump_page+0xb9/0xbe
[<ffffffff81095916>] bad_page+0xd5/0xea
[<ffffffff81095d82>] get_page_from_freelist+0x35b/0x46a
[<ffffffff810961f3>] __alloc_pages_nodemask+0x362/0x662
[<ffffffff810989da>] __do_page_cache_readahead+0x13a/0x267
[<ffffffff81098942>] ? __do_page_cache_readahead+0xa2/0x267
[<ffffffff81098d7b>] ra_submit+0x1c/0x20
[<ffffffff8109900a>] ondemand_readahead+0x28b/0x29a
[<ffffffff81098ee2>] ? ondemand_readahead+0x163/0x29a
[<ffffffff810990ce>] page_cache_sync_readahead+0x38/0x3a
[<ffffffff81091d8a>] generic_file_aio_read+0x2ab/0x67e
[<ffffffffa008cfbe>] nfs_file_read+0xa4/0xc9 [nfs]
[<ffffffff810c22c4>] do_sync_read+0xba/0xfa
[<ffffffff81177a47>] ? security_file_permission+0x7b/0x84
[<ffffffff810c25dd>] ? rw_verify_area+0xab/0xc8
[<ffffffff810c29a4>] vfs_read+0xaa/0x13a
[<ffffffff810c2a79>] sys_read+0x45/0x6c
[<ffffffff813ac37b>] system_call_fastpath+0x16/0x1b
As can be seen, PG_private_2 (== PG_fscache) is set in the page flags.
Instrumenting fscache_mark_pages_cached() to verify whether page->mapping was
set appropriately showed that sometimes it wasn't. This led to the discovery
that sometimes the page has apparently been reclaimed by the time the marker
got to see it.
Reported-by: M. Stevens <m@tippett.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
The compiler, at least for ix86 and m68k, validly warns that the
comparison:
next <= (loff_t)-1
is always true (and it's always true also for x86-64 and probably all
other arches - as long as pgoff_t isn't wider than loff_t). The
intention appears to be to avoid wrapping of "next", so rather than
eliminating the pointless comparison, fix the loop to indeed get exited
when "next" would otherwise wrap.
On m68k the following warning is observed:
fs/fscache/page.c: In function '__fscache_uncache_all_inode_pages':
fs/fscache/page.c:979: warning: comparison is always false due to limited range of data type
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Suresh Jayaraman <sjayaraman@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add an FS-Cache helper to bulk uncache pages on an inode. This will
only work for the circumstance where the pages in the cache correspond
1:1 with the pages attached to an inode's page cache.
This is required for CIFS and NFS: When disabling inode cookie, we were
returning the cookie and setting cifsi->fscache to NULL but failed to
invalidate any previously mapped pages. This resulted in "Bad page
state" errors and manifested in other kind of errors when running
fsstress. Fix it by uncaching mapped pages when we disable the inode
cookie.
This patch should fix the following oops and "Bad page state" errors
seen during fsstress testing.
------------[ cut here ]------------
kernel BUG at fs/cachefiles/namei.c:201!
invalid opcode: 0000 [#1] SMP
Pid: 5, comm: kworker/u:0 Not tainted 2.6.38.7-30.fc15.x86_64 #1 Bochs Bochs
RIP: 0010: cachefiles_walk_to_object+0x436/0x745 [cachefiles]
RSP: 0018:ffff88002ce6dd00 EFLAGS: 00010282
RAX: ffff88002ef165f0 RBX: ffff88001811f500 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000282
RBP: ffff88002ce6dda0 R08: 0000000000000100 R09: ffffffff81b3a300
R10: 0000ffff00066c0a R11: 0000000000000003 R12: ffff88002ae54840
R13: ffff88002ae54840 R14: ffff880029c29c00 R15: ffff88001811f4b0
FS: 00007f394dd32720(0000) GS:ffff88002ef00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fffcb62ddf8 CR3: 000000001825f000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kworker/u:0 (pid: 5, threadinfo ffff88002ce6c000, task ffff88002ce55cc0)
Stack:
0000000000000246 ffff88002ce55cc0 ffff88002ce6dd58 ffff88001815dc00
ffff8800185246c0 ffff88001811f618 ffff880029c29d18 ffff88001811f380
ffff88002ce6dd50 ffffffff814757e4 ffff88002ce6dda0 ffffffff8106ac56
Call Trace:
cachefiles_lookup_object+0x78/0xd4 [cachefiles]
fscache_lookup_object+0x131/0x16d [fscache]
fscache_object_work_func+0x1bc/0x669 [fscache]
process_one_work+0x186/0x298
worker_thread+0xda/0x15d
kthread+0x84/0x8c
kernel_thread_helper+0x4/0x10
RIP cachefiles_walk_to_object+0x436/0x745 [cachefiles]
---[ end trace 1d481c9af1804caa ]---
I tested the uncaching by the following means:
(1) Create a big file on my NFS server (104857600 bytes).
(2) Read the file into the cache with md5sum on the NFS client. Look in
/proc/fs/fscache/stats:
Pages : mrk=25601 unc=0
(3) Open the file for read/write ("bash 5<>/warthog/bigfile"). Look in proc
again:
Pages : mrk=25601 unc=25601
Reported-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-and-Tested-by: Suresh Jayaraman <sjayaraman@suse.de>
cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no CONFIG_WORKQUEUE_DEBUGFS any more, so this code is dead.
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fscache_submit_exclusive_op() adds an operation to the pending list if
other operations are pending. Fix the check for pending ops as n_ops
must be greater than 0 at the point it is checked as it is incremented
immediately before under lock.
Signed-off-by: Akshat Aranya <aranya@nec-labs.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a dummy printk function for the maintenance of unused printks through gcc
format checking, and also so that side-effect checking is maintained too.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 8b8edefa (fscache: convert object to use workqueue instead of
slow-work) made fscache_exit() call unregister_sysctl_table()
unconditionally breaking build when sysctl is disabled. Fix it by
putting it inside CONFIG_SYSCTL.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Make fscache operation to use only workqueue instead of combination of
workqueue and slow-work. FSCACHE_OP_SLOW is dropped and
FSCACHE_OP_FAST is renamed to FSCACHE_OP_ASYNC and uses newly added
fscache_op_wq workqueue to execute op->processor().
fscache_operation_init_slow() is dropped and fscache_operation_init()
now takes @processor argument directly.
* Unbound workqueue is used.
* fscache_retrieval_work() is no longer necessary as OP_ASYNC now does
the equivalent thing.
* sysctl fscache.operation_max_active added to control concurrency.
The default value is nr_cpus clamped between 2 and
WQ_UNBOUND_MAX_ACTIVE.
* debugfs support is dropped for now. Tracing API based debug
facility is planned to be added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Howells <dhowells@redhat.com>
Make fscache object state transition callbacks use workqueue instead
of slow-work. New dedicated unbound CPU workqueue fscache_object_wq
is created. get/put callbacks are renamed and modified to take
@object and called directly from the enqueue wrapper and the work
function. While at it, make all open coded instances of get/put to
use fscache_get/put_object().
* Unbound workqueue is used.
* work_busy() output is printed instead of slow-work flags in object
debugging outputs. They mean basically the same thing bit-for-bit.
* sysctl fscache.object_max_active added to control concurrency. The
default value is nr_cpus clamped between 4 and
WQ_UNBOUND_MAX_ACTIVE.
* slow_work_sleep_till_thread_needed() is replaced with fscache
private implementation fscache_object_sleep_till_congested() which
waits on fscache_object_wq congestion.
* debugfs support is dropped for now. Tracing API based debug
facility is planned to be added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Howells <dhowells@redhat.com>
fscache_write_op() makes unnecessary checks of the page variable to see if it
is NULL. It can't be NULL at those points as the kernel would already have
crashed a little higher up where we examined page->index.
Furthermore, unless radix_tree_gang_lookup_tag() can return 1 but no page, a
NULL pointer crash should not be encountered there as we can only get there if
r_t_g_l_t() returned 1.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/fscache/object-list.c: In function 'fscache_objlist_lookup':
fs/fscache/object-list.c:105: warning: cast to pointer from integer of different size
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Order the debugfs statistics correctly. The values displayed through a
seq_printf() statement should be in the same order as the names in the
format string.
In the 'Lookups' line, objects created ('crt=') and lookups timed out
('tmo=') have their values transposed.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
CONFIG_SLOW_WORK_PROC was changed to CONFIG_SLOW_WORK_DEBUG, but not in all
instances. Change the remaining instances. This makes the debugfs file
display the time mark and the owner's description again.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Sparse complained about this missing spin_unlock()
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the EXPERIMENTAL flag from FS-Cache so that Ubuntu can make use of the
facility.
Signed-off-by: Christian Kujau <lists@nerdbynature.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrew Morton's compiler sees the following warning in FS-Cache:
fs/fscache/object-list.c: In function 'fscache_objlist_lookup':
fs/fscache/object-list.c:94: warning: 'obj' may be used uninitialized in this function
which my compiler doesn't. This is a false positive as obj can only be
used in the comparison against minobj if minobj has been set to something
other than NULL, but for that to happen, obj has to be first set to
something.
Deal with this by preclearing obj too.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Provide nop fscache_stat_d() macro if CONFIG_FSCACHE_STATS=n lest errors like
the following occur:
fs/fscache/cache.c: In function 'fscache_withdraw_cache':
fs/fscache/cache.c:386: error: implicit declaration of function 'fscache_stat_d'
fs/fscache/cache.c:386: error: 'fscache_n_cop_sync_cache' undeclared (first use in this function)
fs/fscache/cache.c:386: error: (Each undeclared identifier is reported only once
fs/fscache/cache.c:386: error: for each function it appears in.)
fs/fscache/cache.c:392: error: 'fscache_n_cop_dissociate_pages' undeclared (first use in this function)
Signed-off-by: David Howells <dhowells@redhat.com>
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>
FS-Cache objects have an FSCACHE_OBJECT_EV_REQUEUE event that can theoretically
be raised to ask the state machine to requeue the object for further processing
before the work function returns to the slow-work facility.
However, fscache_object_work_execute() was clearing that bit before checking
the event mask to see whether the object has any pending events that require it
to be requeued immediately.
Instead, the bit should be cleared after the check and enqueue.
Signed-off-by: David Howells <dhowells@redhat.com>
Start processing an object's operations when that object moves into the DYING
state as the object cannot be destroyed until all its outstanding operations
have completed.
Furthermore, make sure that read and allocation operations handle being woken
up on a dead object. Such events are recorded in the Allocs.abt and
Retrvls.abt statistics as viewable through /proc/fs/fscache/stats.
The code for waiting for object activation for the read and allocation
operations is also extracted into its own function as it is much the same in
all cases, differing only in the stats incremented.
Signed-off-by: David Howells <dhowells@redhat.com>
We must make sure that FSCACHE_COOKIE_LOOKING_UP is cleared on lookup failure
(if an object reaches the LC_DYING state), and we should clear it before
clearing FSCACHE_COOKIE_CREATING.
If this doesn't happen then fscache_wait_for_deferred_lookup() may hold
allocation and retrieval operations indefinitely until they're interrupted by
signals - which in turn pins the dying object until they go away.
Signed-off-by: David Howells <dhowells@redhat.com>
Add a stat counter to count retirement events rather than ordinary release
events (the retire argument to fscache_relinquish_cookie()).
Signed-off-by: David Howells <dhowells@redhat.com>
Handle netfs pages that the vmscan algorithm wants to evict from the pagecache
under OOM conditions, but that are waiting for write to the cache. Under these
conditions, vmscan calls the releasepage() function of the netfs, asking if a
page can be discarded.
The problem is typified by the following trace of a stuck process:
kslowd005 D 0000000000000000 0 4253 2 0x00000080
ffff88001b14f370 0000000000000046 ffff880020d0d000 0000000000000007
0000000000000006 0000000000000001 ffff88001b14ffd8 ffff880020d0d2a8
000000000000ddf0 00000000000118c0 00000000000118c0 ffff880020d0d2a8
Call Trace:
[<ffffffffa00782d8>] __fscache_wait_on_page_write+0x8b/0xa7 [fscache]
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffffa0078240>] ? __fscache_check_page_write+0x63/0x70 [fscache]
[<ffffffffa00b671d>] nfs_fscache_release_page+0x4e/0xc4 [nfs]
[<ffffffffa00927f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff810885d3>] try_to_release_page+0x32/0x3b
[<ffffffff81093203>] shrink_page_list+0x316/0x4ac
[<ffffffff8109372b>] shrink_inactive_list+0x392/0x67c
[<ffffffff813532fa>] ? __mutex_unlock_slowpath+0x100/0x10b
[<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130
[<ffffffff8135330e>] ? mutex_unlock+0x9/0xb
[<ffffffff81093aa2>] shrink_list+0x8d/0x8f
[<ffffffff81093d1c>] shrink_zone+0x278/0x33c
[<ffffffff81052d6c>] ? ktime_get_ts+0xad/0xba
[<ffffffff81094b13>] try_to_free_pages+0x22e/0x392
[<ffffffff81091e24>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e743>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff81089529>] grab_cache_page_write_begin+0x65/0xaa
[<ffffffff8110f8c0>] ext3_write_begin+0x78/0x1eb
[<ffffffff81089ec5>] generic_file_buffered_write+0x109/0x28c
[<ffffffff8103cb69>] ? current_fs_time+0x22/0x29
[<ffffffff8108a509>] __generic_file_aio_write+0x350/0x385
[<ffffffff8108a588>] ? generic_file_aio_write+0x4a/0xae
[<ffffffff8108a59e>] generic_file_aio_write+0x60/0xae
[<ffffffff810b2e82>] do_sync_write+0xe3/0x120
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810b18e1>] ? __dentry_open+0x1a5/0x2b8
[<ffffffff810b1a76>] ? dentry_open+0x82/0x89
[<ffffffffa00e693c>] cachefiles_write_page+0x298/0x335 [cachefiles]
[<ffffffffa0077147>] fscache_write_op+0x178/0x2c2 [fscache]
[<ffffffffa0075656>] fscache_op_execute+0x7a/0xd1 [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
[<ffffffff8102ef83>] ? tg_shares_up+0x171/0x227
[<ffffffff8104be17>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
In the above backtrace, the following is happening:
(1) A page storage operation is being executed by a slow-work thread
(fscache_write_op()).
(2) FS-Cache farms the operation out to the cache to perform
(cachefiles_write_page()).
(3) CacheFiles is then calling Ext3 to perform the actual write, using Ext3's
standard write (do_sync_write()) under KERNEL_DS directly from the netfs
page.
(4) However, for Ext3 to perform the write, it must allocate some memory, in
particular, it must allocate at least one page cache page into which it
can copy the data from the netfs page.
(5) Under OOM conditions, the memory allocator can't immediately come up with
a page, so it uses vmscan to find something to discard
(try_to_free_pages()).
(6) vmscan finds a clean netfs page it might be able to discard (possibly the
one it's trying to write out).
(7) The netfs is called to throw the page away (nfs_release_page()) - but it's
called with __GFP_WAIT, so the netfs decides to wait for the store to
complete (__fscache_wait_on_page_write()).
(8) This blocks a slow-work processing thread - possibly against itself.
The system ends up stuck because it can't write out any netfs pages to the
cache without allocating more memory.
To avoid this, we make FS-Cache cancel some writes that aren't in the middle of
actually being performed. This means that some data won't make it into the
cache this time. To support this, a new FS-Cache function is added
fscache_maybe_release_page() that replaces what the netfs releasepage()
functions used to do with respect to the cache.
The decisions fscache_maybe_release_page() makes are counted and displayed
through /proc/fs/fscache/stats on a line labelled "VmScan". There are four
counters provided: "nos=N" - pages that weren't pending storage; "gon=N" -
pages that were pending storage when we first looked, but weren't by the time
we got the object lock; "bsy=N" - pages that we ignored as they were actively
being written when we looked; and "can=N" - pages that we cancelled the storage
of.
What I'd really like to do is alter the behaviour of the cancellation
heuristics, depending on how necessary it is to expel pages. If there are
plenty of other pages that aren't waiting to be written to the cache that
could be ejected first, then it would be nice to hold up on immediate
cancellation of cache writes - but I don't see a way of doing that.
Signed-off-by: David Howells <dhowells@redhat.com>
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>
Don't delete pending pages from the page-store tracking tree, but rather send
them for another write as they've presumably been updated.
Signed-off-by: David Howells <dhowells@redhat.com>
FS-Cache has two structs internally for keeping track of the internal state of
a cached file: the fscache_cookie struct, which represents the netfs's state,
and fscache_object struct, which represents the cache's state. Each has a
pointer that points to the other (when both are in existence), and each has a
spinlock for pointer maintenance.
Since netfs operations approach these structures from the cookie side, they get
the cookie lock first, then the object lock. Cache operations, on the other
hand, approach from the object side, and get the object lock first. It is not
then permitted for a cache operation to get the cookie lock whilst it is
holding the object lock lest deadlock occur; instead, it must do one of two
things:
(1) increment the cookie usage counter, drop the object lock and then get both
locks in order, or
(2) simply hold the object lock as certain parts of the cookie may not be
altered whilst the object lock is held.
It is also not permitted to follow either pointer without holding the lock at
the end you start with. To break the pointers between the cookie and the
object, both locks must be held.
fscache_write_op(), however, violates the locking rules: It attempts to get the
cookie lock without (a) checking that the cookie pointer is a valid pointer,
and (b) holding the object lock to protect the cookie pointer whilst it follows
it. This is so that it can access the pending page store tree without
interference from __fscache_write_page().
This is fixed by splitting the cookie lock, such that the page store tracking
tree is protected by its own lock, and checking that the cookie pointer is
non-NULL before we attempt to follow it whilst holding the object lock.
The new lock is subordinate to both the cookie lock and the object lock, and so
should be taken after those.
Signed-off-by: David Howells <dhowells@redhat.com>
The object-available state in the object processing state machine (as
processed by fscache_object_available()) can't rely on the cookie to be
available because the FSCACHE_COOKIE_CREATING bit may have been cleared by
fscache_obtained_object() prior to the object being put into the
FSCACHE_OBJECT_AVAILABLE state.
Clearing the FSCACHE_COOKIE_CREATING bit on a cookie permits
__fscache_relinquish_cookie() to proceed and detach the cookie from the
object.
To deal with this, we don't dereference object->cookie in
fscache_object_available() if the object has already been detached.
In addition, a couple of assertions are added into fscache_drop_object() to
make sure the object is unbound from the cookie before it gets there.
Signed-off-by: David Howells <dhowells@redhat.com>
Permit the operations to retrieve data from the cache or to allocate space in
the cache for future writes to be interrupted whilst they're waiting for
permission for the operation to proceed. Typically this wait occurs whilst the
cache object is being looked up on disk in the background.
If an interruption occurs, and the operation has not yet been given the
go-ahead to run, the operation is dequeued and cancelled, and control returns
to the read operation of the netfs routine with none of the requested pages
having been read or in any way marked as known by the cache.
This means that the initial wait is done interruptibly rather than
uninterruptibly.
In addition, extra stats values are made available to show the number of ops
cancelled and the number of cache space allocations interrupted.
Signed-off-by: David Howells <dhowells@redhat.com>
__fscache_write_page() attempts to load the radix tree preallocation pool for
the CPU it is on before calling radix_tree_insert(), as the insertion must be
done inside a pair of spinlocks.
Use of the preallocation pool, however, is contingent on the radix tree being
initialised without __GFP_WAIT specified. __fscache_acquire_cookie() was
passing GFP_NOFS to INIT_RADIX_TREE() - but that includes __GFP_WAIT.
The solution is to AND out __GFP_WAIT.
Additionally, the banner comment to radix_tree_preload() is altered to make
note of this prerequisite. Possibly there should be a WARN_ON() too.
Without this fix, I have seen the following recursive deadlock caused by
radix_tree_insert() attempting to allocate memory inside the spinlocked
region, which resulted in FS-Cache being called back into to release memory -
which required the spinlock already held.
=============================================
[ INFO: possible recursive locking detected ]
2.6.32-rc6-cachefs #24
---------------------------------------------
nfsiod/7916 is trying to acquire lock:
(&cookie->lock){+.+.-.}, at: [<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache]
but task is already holding lock:
(&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache]
other info that might help us debug this:
5 locks held by nfsiod/7916:
#0: (nfsiod){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2
#1: (&task->u.tk_work#2){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2
#2: (&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache]
#3: (&object->lock#2){+.+.-.}, at: [<ffffffffa0076b07>] __fscache_write_page+0x197/0x3f3 [fscache]
#4: (&cookie->stores_lock){+.+...}, at: [<ffffffffa0076b0f>] __fscache_write_page+0x19f/0x3f3 [fscache]
stack backtrace:
Pid: 7916, comm: nfsiod Not tainted 2.6.32-rc6-cachefs #24
Call Trace:
[<ffffffff8105ac7f>] __lock_acquire+0x1649/0x16e3
[<ffffffff81059ded>] ? __lock_acquire+0x7b7/0x16e3
[<ffffffff8100e27d>] ? dump_trace+0x248/0x257
[<ffffffff8105ad70>] lock_acquire+0x57/0x6d
[<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffff8135467c>] _spin_lock+0x2c/0x3b
[<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache]
[<ffffffffa0077eb7>] ? __fscache_check_page_write+0x0/0x71 [fscache]
[<ffffffffa00b4755>] nfs_fscache_release_page+0x86/0xc4 [nfs]
[<ffffffffa00907f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff81087ffb>] try_to_release_page+0x32/0x3b
[<ffffffff81092c2b>] shrink_page_list+0x316/0x4ac
[<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70
[<ffffffff8135451b>] ? _spin_unlock_irq+0x2b/0x31
[<ffffffff81093153>] shrink_inactive_list+0x392/0x67c
[<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70
[<ffffffff810934ca>] shrink_list+0x8d/0x8f
[<ffffffff81093744>] shrink_zone+0x278/0x33c
[<ffffffff81052c70>] ? ktime_get_ts+0xad/0xba
[<ffffffff8109453b>] try_to_free_pages+0x22e/0x392
[<ffffffff8109184c>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e16b>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff810ae24a>] cache_alloc_refill+0x34d/0x6c1
[<ffffffff811bcf74>] ? radix_tree_node_alloc+0x52/0x5c
[<ffffffff810ae929>] kmem_cache_alloc+0xb2/0x118
[<ffffffff811bcf74>] radix_tree_node_alloc+0x52/0x5c
[<ffffffff811bcfd5>] radix_tree_insert+0x57/0x19c
[<ffffffffa0076b53>] __fscache_write_page+0x1e3/0x3f3 [fscache]
[<ffffffffa00b4248>] __nfs_readpage_to_fscache+0x58/0x11e [nfs]
[<ffffffffa009bb77>] nfs_readpage_release+0x34/0x9b [nfs]
[<ffffffffa009c0d9>] nfs_readpage_release_full+0x32/0x4b [nfs]
[<ffffffffa0006cff>] rpc_release_calldata+0x12/0x14 [sunrpc]
[<ffffffffa0006e2d>] rpc_free_task+0x59/0x61 [sunrpc]
[<ffffffffa0006f03>] rpc_async_release+0x10/0x12 [sunrpc]
[<ffffffff810482e5>] worker_thread+0x1ef/0x2e2
[<ffffffff81048290>] ? worker_thread+0x19a/0x2e2
[<ffffffff81352433>] ? thread_return+0x3e/0x101
[<ffffffffa0006ef3>] ? rpc_async_release+0x0/0x12 [sunrpc]
[<ffffffff8104bff5>] ? autoremove_wake_function+0x0/0x34
[<ffffffff81058d25>] ? trace_hardirqs_on+0xd/0xf
[<ffffffff810480f6>] ? worker_thread+0x0/0x2e2
[<ffffffff8104bd21>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8104c2b9>] ? add_wait_queue+0x15/0x44
[<ffffffff8104bca7>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
Signed-off-by: David Howells <dhowells@redhat.com>
Clear the pointers from the fscache_cookie struct to netfs private data after
clearing the pointer to the cookie from the fscache_object struct and
releasing the object lock, rather than before.
This allows the netfs private data pointers to be relied on simply by holding
the object lock, rather than having to hold the cookie lock. This is makes
things simpler as the cookie lock has to be taken before the object lock, but
sometimes the object pointer is all that the code has.
Signed-off-by: David Howells <dhowells@redhat.com>
Count entries to and exits from cache operation table functions. Maintain
these as a single counter that's added to or removed from as appropriate.
Signed-off-by: David Howells <dhowells@redhat.com>
