From 9f10523f891928330b7529da54c1a3cc65180b1a Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 20 Dec 2012 21:52:35 +0000 Subject: FS-Cache: Fix operation state management and accounting 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:[] [] __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: [] nfs_fscache_release_inode_cookie+0x3b/0x47 [nfs] [] nfs_clear_inode+0x3c/0x41 [nfs] [] nfs4_evict_inode+0x2f/0x33 [nfs] [] evict+0xa1/0x15c [] dispose_list+0x2c/0x38 [] prune_icache_sb+0x28c/0x29b [] prune_super+0xd5/0x140 [] shrink_slab+0x102/0x1ab [] balance_pgdat+0x2f2/0x595 [] ? process_timeout+0xb/0xb [] kswapd+0x270/0x289 [] ? __init_waitqueue_head+0x46/0x46 [] ? balance_pgdat+0x595/0x595 [] kthread+0x7f/0x87 [] kernel_thread_helper+0x4/0x10 [] ? finish_task_switch+0x45/0xc0 [] ? retint_restore_args+0xe/0xe [] ? __init_kthread_worker+0x53/0x53 [] ? gs_change+0xb/0xb Signed-off-by: David Howells --- Documentation/filesystems/caching/backend-api.txt | 26 ++++++++++++++++++++++- Documentation/filesystems/caching/operations.txt | 2 +- 2 files changed, 26 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt index 382d52cdaf2..f4769b9399d 100644 --- a/Documentation/filesystems/caching/backend-api.txt +++ b/Documentation/filesystems/caching/backend-api.txt @@ -419,7 +419,10 @@ performed on the denizens of the cache. These are held in a structure of type: If an I/O error occurs, fscache_io_error() should be called and -ENOBUFS returned if possible or fscache_end_io() called with a suitable error - code.. + code. + + fscache_put_retrieval() should be called after a page or pages are dealt + with. This will complete the operation when all pages are dealt with. (*) Request pages be read from cache [mandatory]: @@ -526,6 +529,27 @@ FS-Cache provides some utilities that a cache backend may make use of: error value should be 0 if successful and an error otherwise. + (*) Record that one or more pages being retrieved or allocated have been dealt + with: + + void fscache_retrieval_complete(struct fscache_retrieval *op, + int n_pages); + + This is called to record the fact that one or more pages have been dealt + with and are no longer the concern of this operation. When the number of + pages remaining in the operation reaches 0, the operation will be + completed. + + + (*) Record operation completion: + + void fscache_op_complete(struct fscache_operation *op); + + This is called to record the completion of an operation. This deducts + this operation from the parent object's run state, potentially permitting + one or more pending operations to start running. + + (*) Set highest store limit: void fscache_set_store_limit(struct fscache_object *object, diff --git a/Documentation/filesystems/caching/operations.txt b/Documentation/filesystems/caching/operations.txt index b6b070c57cb..bee2a5f93d6 100644 --- a/Documentation/filesystems/caching/operations.txt +++ b/Documentation/filesystems/caching/operations.txt @@ -174,7 +174,7 @@ Operations are used through the following procedure: necessary (the object might have died whilst the thread was waiting). When it has finished doing its processing, it should call - fscache_put_operation() on it. + fscache_op_complete() and fscache_put_operation() on it. (4) The operation holds an effective lock upon the object, preventing other exclusive ops conflicting until it is released. The operation can be -- cgit v1.2.3-18-g5258 From ef778e7ae67cd426c30cad43378b908f5eb0bad5 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 20 Dec 2012 21:52:36 +0000 Subject: FS-Cache: Provide proper invalidation 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 --- Documentation/filesystems/caching/backend-api.txt | 12 ++++++ Documentation/filesystems/caching/netfs-api.txt | 46 +++++++++++++++++++---- Documentation/filesystems/caching/object.txt | 23 ++++++++---- 3 files changed, 65 insertions(+), 16 deletions(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt index f4769b9399d..d78bab9622c 100644 --- a/Documentation/filesystems/caching/backend-api.txt +++ b/Documentation/filesystems/caching/backend-api.txt @@ -308,6 +308,18 @@ performed on the denizens of the cache. These are held in a structure of type: obtained by calling object->cookie->def->get_aux()/get_attr(). + (*) Invalidate data object [mandatory]: + + int (*invalidate_object)(struct fscache_operation *op) + + This is called to invalidate a data object (as pointed to by op->object). + All the data stored for this object should be discarded and an + attr_changed operation should be performed. The caller will follow up + with an object update operation. + + fscache_op_complete() must be called on op before returning. + + (*) Discard object [mandatory]: void (*drop_object)(struct fscache_object *object) diff --git a/Documentation/filesystems/caching/netfs-api.txt b/Documentation/filesystems/caching/netfs-api.txt index 7cc6bf2871e..97e6c0ecc5e 100644 --- a/Documentation/filesystems/caching/netfs-api.txt +++ b/Documentation/filesystems/caching/netfs-api.txt @@ -35,8 +35,9 @@ This document contains the following sections: (12) Index and data file update (13) Miscellaneous cookie operations (14) Cookie unregistration - (15) Index and data file invalidation - (16) FS-Cache specific page flags. + (15) Index invalidation + (16) Data file invalidation + (17) FS-Cache specific page flags. ============================= @@ -767,13 +768,42 @@ the cookies for "child" indices, objects and pages have been relinquished first. -================================ -INDEX AND DATA FILE INVALIDATION -================================ +================== +INDEX INVALIDATION +================== + +There is no direct way to invalidate an index subtree. To do this, the caller +should relinquish and retire the cookie they have, and then acquire a new one. + + +====================== +DATA FILE INVALIDATION +====================== + +Sometimes it will be necessary to invalidate an object that contains data. +Typically this will be necessary when the server tells the netfs of a foreign +change - at which point the netfs has to throw away all the state it had for an +inode and reload from the server. + +To indicate that a cache object should be invalidated, the following function +can be called: + + void fscache_invalidate(struct fscache_cookie *cookie); + +This can be called with spinlocks held as it defers the work to a thread pool. +All extant storage, retrieval and attribute change ops at this point are +cancelled and discarded. Some future operations will be rejected until the +cache has had a chance to insert a barrier in the operations queue. After +that, operations will be queued again behind the invalidation operation. + +The invalidation operation will perform an attribute change operation and an +auxiliary data update operation as it is very likely these will have changed. + +Using the following function, the netfs can wait for the invalidation operation +to have reached a point at which it can start submitting ordinary operations +once again: -There is no direct way to invalidate an index subtree or a data file. To do -this, the caller should relinquish and retire the cookie they have, and then -acquire a new one. + void fscache_wait_on_invalidate(struct fscache_cookie *cookie); =========================== diff --git a/Documentation/filesystems/caching/object.txt b/Documentation/filesystems/caching/object.txt index 58313348da8..100ff41127e 100644 --- a/Documentation/filesystems/caching/object.txt +++ b/Documentation/filesystems/caching/object.txt @@ -216,7 +216,14 @@ servicing netfs requests: The normal running state. In this state, requests the netfs makes will be passed on to the cache. - (6) State FSCACHE_OBJECT_UPDATING. + (6) State FSCACHE_OBJECT_INVALIDATING. + + The object is undergoing invalidation. When the state comes here, it + discards all pending read, write and attribute change operations as it is + going to clear out the cache entirely and reinitialise it. It will then + continue to the FSCACHE_OBJECT_UPDATING state. + + (7) State FSCACHE_OBJECT_UPDATING. The state machine comes here to update the object in the cache from the netfs's records. This involves updating the auxiliary data that is used @@ -225,13 +232,13 @@ servicing netfs requests: And there are terminal states in which an object cleans itself up, deallocates memory and potentially deletes stuff from disk: - (7) State FSCACHE_OBJECT_LC_DYING. + (8) State FSCACHE_OBJECT_LC_DYING. The object comes here if it is dying because of a lookup or creation error. This would be due to a disk error or system error of some sort. Temporary data is cleaned up, and the parent is released. - (8) State FSCACHE_OBJECT_DYING. + (9) State FSCACHE_OBJECT_DYING. The object comes here if it is dying due to an error, because its parent cookie has been relinquished by the netfs or because the cache is being @@ -241,27 +248,27 @@ memory and potentially deletes stuff from disk: can destroy themselves. This object waits for all its children to go away before advancing to the next state. - (9) State FSCACHE_OBJECT_ABORT_INIT. +(10) State FSCACHE_OBJECT_ABORT_INIT. The object comes to this state if it was waiting on its parent in FSCACHE_OBJECT_INIT, but its parent died. The object will destroy itself so that the parent may proceed from the FSCACHE_OBJECT_DYING state. -(10) State FSCACHE_OBJECT_RELEASING. -(11) State FSCACHE_OBJECT_RECYCLING. +(11) State FSCACHE_OBJECT_RELEASING. +(12) State FSCACHE_OBJECT_RECYCLING. The object comes to one of these two states when dying once it is rid of all its children, if it is dying because the netfs relinquished its cookie. In the first state, the cached data is expected to persist, and in the second it will be deleted. -(12) State FSCACHE_OBJECT_WITHDRAWING. +(13) State FSCACHE_OBJECT_WITHDRAWING. The object transits to this state if the cache decides it wants to withdraw the object from service, perhaps to make space, but also due to error or just because the whole cache is being withdrawn. -(13) State FSCACHE_OBJECT_DEAD. +(14) State FSCACHE_OBJECT_DEAD. The object transits to this state when the in-memory object record is ready to be deleted. The object processor shouldn't ever see an object in -- cgit v1.2.3-18-g5258 From b9f61c3c0c8daed9844870bc9358e6d9fdb7eb61 Mon Sep 17 00:00:00 2001 From: Marco Stornelli Date: Sat, 15 Dec 2012 12:00:38 +0100 Subject: documentation: drop vmtruncate Removed vmtruncate Signed-off-by: Marco Stornelli Signed-off-by: Al Viro --- Documentation/filesystems/Locking | 6 ------ Documentation/filesystems/porting | 2 +- Documentation/filesystems/vfs.txt | 11 ----------- 3 files changed, 1 insertion(+), 18 deletions(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index e540a24e5d0..f48e0c6b4c4 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -80,7 +80,6 @@ rename: yes (all) (see below) readlink: no follow_link: no put_link: no -truncate: yes (see below) setattr: yes permission: no (may not block if called in rcu-walk mode) get_acl: no @@ -96,11 +95,6 @@ atomic_open: yes Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on victim. cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. - ->truncate() is never called directly - it's a callback, not a -method. It's called by vmtruncate() - deprecated library function used by -->setattr(). Locking information above applies to that call (i.e. is -inherited from ->setattr() - vmtruncate() is used when ATTR_SIZE had been -passed). See Documentation/filesystems/directory-locking for more detailed discussion of the locking scheme for directory operations. diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index 0742feebc6e..0472c31c163 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -281,7 +281,7 @@ ext2_write_failed and callers for an example. [mandatory] - ->truncate is going away. The whole truncate sequence needs to be + ->truncate is gone. The whole truncate sequence needs to be implemented in ->setattr, which is now mandatory for filesystems implementing on-disk size changes. Start with a copy of the old inode_setattr and vmtruncate, and the reorder the vmtruncate + foofs_vmtruncate sequence to diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 2ee133e030c..e3869098163 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -350,7 +350,6 @@ struct inode_operations { int (*readlink) (struct dentry *, char __user *,int); void * (*follow_link) (struct dentry *, struct nameidata *); void (*put_link) (struct dentry *, struct nameidata *, void *); - void (*truncate) (struct inode *); int (*permission) (struct inode *, int); int (*get_acl)(struct inode *, int); int (*setattr) (struct dentry *, struct iattr *); @@ -431,16 +430,6 @@ otherwise noted. started might not be in the page cache at the end of the walk). - truncate: Deprecated. This will not be called if ->setsize is defined. - Called by the VFS to change the size of a file. The - i_size field of the inode is set to the desired size by the - VFS before this method is called. This method is called by - the truncate(2) system call and related functionality. - - Note: ->truncate and vmtruncate are deprecated. Do not add new - instances/calls of these. Filesystems should be converted to do their - truncate sequence via ->setattr(). - permission: called by the VFS to check for access rights on a POSIX-like filesystem. -- cgit v1.2.3-18-g5258