From c435ee34551e1f5a02a253ca8e235287efd2727c Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 2 Nov 2017 15:27:49 +0000 Subject: afs: Overhaul the callback handling Overhaul the AFS callback handling by the following means: (1) Don't give up callback promises on vnodes that we are no longer using, rather let them just expire on the server or let the server break them. This is actually more efficient for the server as the callback lookup is expensive if there are lots of extant callbacks. (2) Only give up the callback promises we have from a server when the server record is destroyed. Then we can just give up *all* the callback promises on it in one go. (3) Servers can end up being shared between cells if cells are aliased, so don't add all the vnodes being backed by a particular server into a big FID-indexed tree on that server as there may be duplicates. Instead have each volume instance (~= superblock) register an interest in a server as it starts to make use of it and use this to allow the processor for callbacks from the server to find the superblock and thence the inode corresponding to the FID being broken by means of ilookup_nowait(). (4) Rather than iterating over the entire callback list when a mass-break comes in from the server, maintain a counter of mass-breaks in afs_server (cb_seq) and make afs_validate() check it against the copy in afs_vnode. It would be nice not to have to take a read_lock whilst doing this, but that's tricky without using RCU. (5) Save a ref on the fileserver we're using for a call in the afs_call struct so that we can access its cb_s_break during call decoding. (6) Write-lock around callback and status storage in a vnode and read-lock around getattr so that we don't see the status mid-update. This has the following consequences: (1) Data invalidation isn't seen until someone calls afs_validate() on a vnode. Unfortunately, we need to use a key to query the server, but getting one from a background thread is tricky without caching loads of keys all over the place. (2) Mass invalidation isn't seen until someone calls afs_validate(). (3) Callback breaking is going to hit the inode_hash_lock quite a bit. Could this be replaced with rcu_read_lock() since inodes are destroyed under RCU conditions. Signed-off-by: David Howells --- fs/afs/security.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) (limited to 'fs/afs/security.c') diff --git a/fs/afs/security.c b/fs/afs/security.c index faca66227ecf..7cc61c8b748b 100644 --- a/fs/afs/security.c +++ b/fs/afs/security.c @@ -115,6 +115,7 @@ void afs_clear_permits(struct afs_vnode *vnode) mutex_lock(&vnode->permits_lock); permits = vnode->permits; RCU_INIT_POINTER(vnode->permits, NULL); + vnode->cb_break++; mutex_unlock(&vnode->permits_lock); if (permits) @@ -264,8 +265,7 @@ static int afs_check_permit(struct afs_vnode *vnode, struct key *key, * (the post-processing will cache the result on auth_vnode) */ _debug("no valid permit"); - set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags); - ret = afs_vnode_fetch_status(vnode, auth_vnode, key); + ret = afs_vnode_fetch_status(vnode, auth_vnode, key, true); if (ret < 0) { iput(&auth_vnode->vfs_inode); *_access = 0; @@ -304,14 +304,9 @@ int afs_permission(struct inode *inode, int mask) return PTR_ERR(key); } - /* if the promise has expired, we need to check the server again */ - if (!vnode->cb_promised) { - _debug("not promised"); - ret = afs_vnode_fetch_status(vnode, NULL, key); - if (ret < 0) - goto error; - _debug("new promise [fl=%lx]", vnode->flags); - } + ret = afs_validate(vnode, key); + if (ret < 0) + goto error; /* check the permits to see if we've got one yet */ ret = afs_check_permit(vnode, key, &access); -- cgit v1.2.3-58-ga151