BMC/Intel-BMC/linux.git/fs/fscache/page.c, branch dev

FS-Cache: Retain the netfs context in the retrieval op earlier

2015-04-02T13:28:53+00:00

Now that the retrieval operation may be disposed of by fscache_put_operation() before we actually set the context, the retrieval-specific cleanup operation can produce a NULL-pointer dereference when it tries to unconditionally clean up the netfs context. Given that it is expected that we'll get at least as far as the place where we currently set the context pointer and it is unlikely we'll go through the error handling paths prior to that point, retain the context right from the point that the retrieval op is allocated. Concomitant to this, we need to retain the cookie pointer in the retrieval op also so that we can call the netfs to release its context in the release method. In addition, we might now get into fscache_release_retrieval_op() with the op only initialised. To this end, set the operation to DEAD only after the release method has been called and skip the n_pages test upon cleanup if the op is still in the INITIALISED state. Without these changes, the following oops might be seen: BUG: unable to handle kernel NULL pointer dereference at 00000000000000b8 ... RIP: 0010:[] fscache_release_retrieval_op+0xae/0x100 ... Call Trace: [] fscache_put_operation+0x117/0x2e0 [] __fscache_read_or_alloc_pages+0x351/0x3ac [] __nfs_readpages_from_fscache+0x59/0xbf [nfs] [] nfs_readpages+0x10c/0x185 [nfs] [] ? alloc_pages_current+0x119/0x13e [] ? __page_cache_alloc+0xfb/0x10a [] __do_page_cache_readahead+0x188/0x22c [] ondemand_readahead+0x29e/0x2af [] page_cache_sync_readahead+0x38/0x3a [] generic_file_read_iter+0x1a2/0x55a [] ? nfs_revalidate_mapping+0xd6/0x288 [nfs] [] nfs_file_read+0x49/0x70 [nfs] [] new_sync_read+0x78/0x9c [] __vfs_read+0x13/0x38 [] vfs_read+0x95/0x121 [] SyS_read+0x4c/0x8a [] system_call_fastpath+0x12/0x17 Signed-off-by: David Howells Reviewed-by: Steve Dickson Acked-by: Jeff Layton

FS-Cache: The operation cancellation method needs calling in more places

2015-04-02T13:28:53+00:00

Any time an incomplete operation is cancelled, the operation cancellation function needs to be called to clean up. This is currently being passed directly to some of the functions that might want to call it, but not all. Instead, pass the cancellation method pointer to the fscache_operation_init() and have that cache it in the operation struct. Further, plug in a dummy cancellation handler if the caller declines to set one as this allows us to call the function unconditionally (the extra overhead isn't worth bothering about as we don't expect to be calling this typically). The cancellation method must thence be called everywhere the CANCELLED state is set. Note that we call it *before* setting the CANCELLED state such that the method can use the old state value to guide its operation. fscache_do_cancel_retrieval() needs moving higher up in the sources so that the init function can use it now. Without this, the following oops may be seen: FS-Cache: Assertion failed FS-Cache: 3 == 0 is false ------------[ cut here ]------------ kernel BUG at ../fs/fscache/page.c:261! ... RIP: 0010:[] fscache_release_retrieval_op+0x77/0x100 [] fscache_put_operation+0x114/0x2da [] __fscache_read_or_alloc_pages+0x358/0x3b3 [] __nfs_readpages_from_fscache+0x59/0xbf [nfs] [] nfs_readpages+0x10c/0x185 [nfs] [] ? alloc_pages_current+0x119/0x13e [] ? __page_cache_alloc+0xfb/0x10a [] __do_page_cache_readahead+0x188/0x22c [] ondemand_readahead+0x29e/0x2af [] page_cache_sync_readahead+0x38/0x3a [] generic_file_read_iter+0x1a2/0x55a [] ? nfs_revalidate_mapping+0xd6/0x288 [nfs] [] nfs_file_read+0x49/0x70 [nfs] [] new_sync_read+0x78/0x9c [] __vfs_read+0x13/0x38 [] vfs_read+0x95/0x121 [] SyS_read+0x4c/0x8a [] system_call_fastpath+0x12/0x17 The assertion is showing that the remaining number of pages (n_pages) is not 0 when the operation is being released. Signed-off-by: David Howells Reviewed-by: Steve Dickson Acked-by: Jeff Layton

FS-Cache: Put an aborted initialised op so that it is accounted correctly

2015-04-02T13:28:53+00:00

Call fscache_put_operation() or a wrapper on any op that has gone through fscache_operation_init() so that the accounting shown in /proc is done correctly, specifically fscache_n_op_release. fscache_put_operation() therefore now allows an op in the INITIALISED state as well as in the CANCELLED and COMPLETE states. Note that this means that an operation can get put that doesn't have its ->object pointer filled in, so anything that depends on the object needs to be conditional in fscache_put_operation(). Signed-off-by: David Howells Reviewed-by: Steve Dickson Acked-by: Jeff Layton

FS-Cache: Permit fscache_cancel_op() to cancel in-progress operations too

2015-04-02T13:28:53+00:00

Currently, fscache_cancel_op() only cancels pending operations - attempts to cancel in-progress operations are ignored. This leads to a problem in fscache_wait_for_operation_activation() whereby the wait is terminated, but the object has been killed. The check at the end of the function now triggers because it's no longer contingent on the cache having produced an I/O error since the commit that fixed the logic error in fscache_object_is_dead(). The result of the check is that it tries to cancel the operation - but since the object may not be pending by this point, the cancellation request may be ignored - with the result that the the object is just put by the caller and fscache_put_operation has an assertion failure because the operation isn't in either the COMPLETE or the CANCELLED states. To fix this, we permit in-progress ops to be cancelled under some circumstances. The bug results in an oops that looks something like this: FS-Cache: fscache_wait_for_operation_activation() = -ENOBUFS [obj dead 3] FS-Cache: FS-Cache: Assertion failed FS-Cache: 3 == 5 is false ------------[ cut here ]------------ kernel BUG at ../fs/fscache/operation.c:432! ... RIP: 0010:[] fscache_put_operation+0xf2/0x2cd Call Trace: [] __fscache_read_or_alloc_pages+0x2ec/0x3b3 [] __nfs_readpages_from_fscache+0x59/0xbf [nfs] [] nfs_readpages+0x10c/0x185 [nfs] [] ? alloc_pages_current+0x119/0x13e [] ? __page_cache_alloc+0xfb/0x10a [] __do_page_cache_readahead+0x188/0x22c [] ondemand_readahead+0x29e/0x2af [] page_cache_sync_readahead+0x38/0x3a [] generic_file_read_iter+0x1a2/0x55a [] ? nfs_revalidate_mapping+0xd6/0x288 [nfs] [] nfs_file_read+0x49/0x70 [nfs] [] new_sync_read+0x78/0x9c [] __vfs_read+0x13/0x38 [] vfs_read+0x95/0x121 [] SyS_read+0x4c/0x8a [] system_call_fastpath+0x12/0x17 Signed-off-by: David Howells Reviewed-by: Steve Dickson Acked-by: Jeff Layton

FS-Cache: fscache_object_is_dead() has wrong logic, kill it

2015-04-02T13:28:53+00:00

fscache_object_is_dead() returns true only if the object is marked dead and the cache got an I/O error. This should be a logical OR instead. Since two of the callers got split up into handling for separate subcases, expand the other callers and kill the function. This is probably the right thing to do anyway since one of the subcases isn't about the object at all, but rather about the cache. Signed-off-by: David Howells Reviewed-by: Steve Dickson Acked-by: Jeff Layton

FS-Cache: refcount becomes corrupt under vma pressure.

2014-09-17T21:41:40+00:00

In rare cases under heavy VMA pressure the ref count for a fscache cookie becomes corrupt. In this case we decrement ref count even if we fail before incrementing the refcount. FS-Cache: Assertion failed bnode-eca5f9c6/syslog 0 > 0 is false ------------[ cut here ]------------ kernel BUG at fs/fscache/cookie.c:519! invalid opcode: 0000 [#1] SMP Call Trace: [] __fscache_relinquish_cookie+0x50/0x220 [fscache] [] ceph_fscache_unregister_inode_cookie+0x3e/0x50 [ceph] [] ceph_destroy_inode+0x33/0x200 [ceph] [] ? __fsnotify_inode_delete+0xe/0x10 [] destroy_inode+0x3c/0x70 [] evict+0x111/0x180 [] iput+0x103/0x190 [] __dentry_kill+0x1c8/0x220 [] shrink_dentry_list+0xf1/0x250 [] prune_dcache_sb+0x4c/0x60 [] super_cache_scan+0xff/0x170 [] shrink_slab_node+0x140/0x2c0 [] shrink_slab+0x8a/0x130 [] balance_pgdat+0x3e2/0x5d0 [] kswapd+0x16a/0x4a0 [] ? __wake_up_sync+0x20/0x20 [] ? balance_pgdat+0x5d0/0x5d0 [] kthread+0xc9/0xe0 [] ? ftrace_raw_event_xen_mmu_release_ptpage+0x70/0x90 [] ? flush_kthread_worker+0xb0/0xb0 [] ret_from_fork+0x7c/0xb0 [] ? flush_kthread_worker+0xb0/0xb0 RIP [] __fscache_disable_cookie+0x1db/0x210 [fscache] RSP ---[ end trace 254d0d7c74a01f25 ]--- Signed-off-by: Milosz Tanski Signed-off-by: David Howells

FS-Cache: Timeout for releasepage()

2014-08-27T14:24:06+00:00

This is meant to avoid a recusive hang caused by underlying filesystem trying to grab a free page and causing a write-out. INFO: task kworker/u30:7:28375 blocked for more than 120 seconds. Not tainted 3.15.0-virtual #74 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u30:7 D 0000000000000000 0 28375 2 0x00000000 Workqueue: fscache_operation fscache_op_work_func [fscache] ffff88000b147148 0000000000000046 0000000000000000 ffff88000b1471c8 ffff8807aa031820 0000000000014040 ffff88000b147fd8 0000000000014040 ffff880f0c50c860 ffff8807aa031820 ffff88000b147158 ffff88007be59cd0 Call Trace: [] schedule+0x29/0x70 [] __fscache_wait_on_page_write+0x55/0x90 [fscache] [] ? __wake_up_sync+0x20/0x20 [] __fscache_maybe_release_page+0x65/0x1e0 [fscache] [] ceph_releasepage+0x83/0x100 [ceph] [] ? anon_vma_fork+0x130/0x130 [] try_to_release_page+0x32/0x50 [] shrink_page_list+0x7e6/0x9d0 [] ? isolate_lru_pages.isra.73+0x78/0x1e0 [] shrink_inactive_list+0x252/0x4c0 [] shrink_lruvec+0x3e1/0x670 [] shrink_zone+0x3f/0x110 [] do_try_to_free_pages+0x1d6/0x450 [] ? zone_statistics+0x99/0xc0 [] try_to_free_pages+0xc4/0x180 [] __alloc_pages_nodemask+0x6b2/0xa60 [] ? __find_get_block+0xbe/0x250 [] ? wake_up_bit+0x2e/0x40 [] alloc_pages_current+0xb3/0x180 [] __page_cache_alloc+0xb7/0xd0 [] grab_cache_page_write_begin+0x7c/0xe0 [] ? ext4_mark_inode_dirty+0x82/0x220 [] ext4_da_write_begin+0x89/0x2d0 [] generic_perform_write+0xbe/0x1d0 [] ? update_time+0x81/0xc0 [] ? mnt_clone_write+0x12/0x30 [] __generic_file_aio_write+0x1ce/0x3f0 [] generic_file_aio_write+0x5e/0xe0 [] ext4_file_write+0x9f/0x410 [] ? ext4_file_open+0x66/0x180 [] do_sync_write+0x5a/0x90 [] cachefiles_write_page+0x149/0x430 [cachefiles] [] ? radix_tree_gang_lookup_tag+0x89/0xd0 [] fscache_write_op+0x222/0x3b0 [fscache] [] fscache_op_work_func+0x3a/0x100 [fscache] [] process_one_work+0x179/0x4a0 [] worker_thread+0x11b/0x370 [] ? manage_workers.isra.21+0x2e0/0x2e0 [] kthread+0xc9/0xe0 [] ? ftrace_raw_event_xen_mmu_release_ptpage+0x70/0x90 [] ? flush_kthread_worker+0xb0/0xb0 [] ret_from_fork+0x7c/0xb0 [] ? flush_kthread_worker+0xb0/0xb0 Signed-off-by: Milosz Tanski Signed-off-by: David Howells

sched: Remove proliferation of wait_on_bit() action functions

2014-07-16T13:10:39+00:00

The current "wait_on_bit" interface requires an 'action' function to be provided which does the actual waiting. There are over 20 such functions, many of them identical. Most cases can be satisfied by one of just two functions, one which uses io_schedule() and one which just uses schedule(). So: Rename wait_on_bit and wait_on_bit_lock to wait_on_bit_action and wait_on_bit_lock_action to make it explicit that they need an action function. Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io which are *not* given an action function but implicitly use a standard one. The decision to error-out if a signal is pending is now made based on the 'mode' argument rather than being encoded in the action function. All instances of the old wait_on_bit and wait_on_bit_lock which can use the new version have been changed accordingly and their action functions have been discarded. wait_on_bit{_lock} does not return any specific error code in the event of a signal so the caller must check for non-zero and interpolate their own error code as appropriate. The wait_on_bit() call in __fscache_wait_on_invalidate() was ambiguous as it specified TASK_UNINTERRUPTIBLE but used fscache_wait_bit_interruptible as an action function. David Howells confirms this should be uniformly "uninterruptible" The main remaining user of wait_on_bit{,_lock}_action is NFS which needs to use a freezer-aware schedule() call. A comment in fs/gfs2/glock.c notes that having multiple 'action' functions is useful as they display differently in the 'wchan' field of 'ps'. (and /proc/$PID/wchan). As the new bit_wait{,_io} functions are tagged "__sched", they will not show up at all, but something higher in the stack. So the distinction will still be visible, only with different function names (gds2_glock_wait versus gfs2_glock_dq_wait in the gfs2/glock.c case). Since first version of this patch (against 3.15) two new action functions appeared, on in NFS and one in CIFS. CIFS also now uses an action function that makes the same freezer aware schedule call as NFS. Signed-off-by: NeilBrown Acked-by: David Howells (fscache, keys) Acked-by: Steven Whitehouse (gfs2) Acked-by: Peter Zijlstra Cc: Oleg Nesterov Cc: Steve French Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown Signed-off-by: Ingo Molnar

fs/fscache: convert printk to pr_foo()

2014-06-04T23:53:51+00:00

All printk converted to pr_foo() except internal.h: printk(KERN_DEBUG Coalesce formats. Add pr_fmt Signed-off-by: Fabian Frederick Cc: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

FS-Cache: Provide the ability to enable/disable cookies

2013-09-27T17:40:25+00:00

Provide the ability to enable and disable fscache cookies. A disabled cookie will reject or ignore further requests to: Acquire a child cookie Invalidate and update backing objects Check the consistency of a backing object Allocate storage for backing page Read backing pages Write to backing pages but still allows: Checks/waits on the completion of already in-progress objects Uncaching of pages Relinquishment of cookies Two new operations are provided: (1) Disable a cookie: void fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate); If the cookie is not already disabled, this locks the cookie against other dis/enablement ops, marks the cookie as being disabled, discards or invalidates any backing objects and waits for cessation of activity on any associated object. This is a wrapper around a chunk split out of fscache_relinquish_cookie(), but it reinitialises the cookie such that it can be reenabled. All possible failures are handled internally. The caller should consider calling fscache_uncache_all_inode_pages() afterwards to make sure all page markings are cleared up. (2) Enable a cookie: void fscache_enable_cookie(struct fscache_cookie *cookie, bool (*can_enable)(void *data), void *data) If the cookie is not already enabled, this locks the cookie against other dis/enablement ops, invokes can_enable() and, if the cookie is not an index cookie, will begin the procedure of acquiring backing objects. The optional can_enable() function is passed the data argument and returns a ruling as to whether or not enablement should actually be permitted to begin. All possible failures are handled internally. The cookie will only be marked as enabled if provisional backing objects are allocated. A later patch will introduce these to NFS. Cookie enablement during nfs_open() is then contingent on i_writecount <= 0. can_enable() checks for a race between open(O_RDONLY) and open(O_WRONLY/O_RDWR). This simplifies NFS's cookie handling and allows us to get rid of open(O_RDONLY) accidentally introducing caching to an inode that's open for writing already. One operation has its API modified: (3) Acquire a cookie. struct fscache_cookie *fscache_acquire_cookie( struct fscache_cookie *parent, const struct fscache_cookie_def *def, void *netfs_data, bool enable); This now has an additional argument that indicates whether the requested cookie should be enabled by default. It doesn't need the can_enable() function because the caller must prevent multiple calls for the same netfs object and it doesn't need to take the enablement lock because no one else can get at the cookie before this returns. Signed-off-by: David Howells