• David Howells's avatar
    FS-Cache: Use radix tree preload correctly in tracking of pages to be stored · b34df792
    David Howells authored
    __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: default avatarDavid Howells <dhowells@redhat.com>
    b34df792
cookie.c 13.2 KB