From f642404a0436a50912c218009ccc7856d48d784c Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 13 May 2019 16:14:32 +0100 Subject: afs: Make vnode->cb_interest RCU safe Use RCU-based freeing for afs_cb_interest struct objects and use RCU on vnode->cb_interest. Use that change to allow afs_check_validity() to use read_seqbegin_or_lock() instead of read_seqlock_excl(). This also requires the caller of afs_check_validity() to hold the RCU read lock across the call. Signed-off-by: David Howells --- fs/afs/inode.c | 81 ++++++++++++++++++++++++++++++++++++---------------------- 1 file changed, 50 insertions(+), 31 deletions(-) (limited to 'fs/afs/inode.c') diff --git a/fs/afs/inode.c b/fs/afs/inode.c index 5c95da7d5f3d..ba35b4824408 100644 --- a/fs/afs/inode.c +++ b/fs/afs/inode.c @@ -139,9 +139,10 @@ static int afs_inode_init_from_status(struct afs_vnode *vnode, struct key *key, vnode->cb_expires_at = ktime_get_real_seconds(); } else { vnode->cb_expires_at = scb->callback.expires_at; - old_cbi = vnode->cb_interest; + old_cbi = rcu_dereference_protected(vnode->cb_interest, + lockdep_is_held(&vnode->cb_lock.lock)); if (cbi != old_cbi) - vnode->cb_interest = afs_get_cb_interest(cbi); + rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(cbi)); else old_cbi = NULL; set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags); @@ -245,9 +246,10 @@ static void afs_apply_callback(struct afs_fs_cursor *fc, if (!afs_cb_is_broken(cb_break, vnode, fc->cbi)) { vnode->cb_expires_at = cb->expires_at; - old = vnode->cb_interest; + old = rcu_dereference_protected(vnode->cb_interest, + lockdep_is_held(&vnode->cb_lock.lock)); if (old != fc->cbi) { - vnode->cb_interest = afs_get_cb_interest(fc->cbi); + rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(fc->cbi)); afs_put_cb_interest(afs_v2net(vnode), old); } set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags); @@ -565,36 +567,46 @@ void afs_zap_data(struct afs_vnode *vnode) */ bool afs_check_validity(struct afs_vnode *vnode) { + struct afs_cb_interest *cbi; + struct afs_server *server; + struct afs_volume *volume = vnode->volume; time64_t now = ktime_get_real_seconds(); bool valid; + unsigned int cb_break, cb_s_break, cb_v_break; + int seq = 0; - /* Quickly check the callback state. Ideally, we'd use read_seqbegin - * here, but we have no way to pass the net namespace to the RCU - * cleanup for the server record. - */ - read_seqlock_excl(&vnode->cb_lock); - - if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) { - if (vnode->cb_s_break != vnode->cb_interest->server->cb_s_break || - vnode->cb_v_break != vnode->volume->cb_v_break) { - vnode->cb_s_break = vnode->cb_interest->server->cb_s_break; - vnode->cb_v_break = vnode->volume->cb_v_break; - valid = false; - } else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) { - valid = false; - } else if (vnode->cb_expires_at - 10 <= now) { - valid = false; - } else { + do { + read_seqbegin_or_lock(&vnode->cb_lock, &seq); + cb_v_break = READ_ONCE(volume->cb_v_break); + cb_break = vnode->cb_break; + + if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) { + cbi = rcu_dereference(vnode->cb_interest); + server = rcu_dereference(cbi->server); + cb_s_break = READ_ONCE(server->cb_s_break); + + if (vnode->cb_s_break != cb_s_break || + vnode->cb_v_break != cb_v_break) { + vnode->cb_s_break = cb_s_break; + vnode->cb_v_break = cb_v_break; + valid = false; + } else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) { + valid = false; + } else if (vnode->cb_expires_at - 10 <= now) { + valid = false; + } else { + valid = true; + } + } else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) { valid = true; + } else { + vnode->cb_v_break = cb_v_break; + valid = false; } - } else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) { - valid = true; - } else { - vnode->cb_v_break = vnode->volume->cb_v_break; - valid = false; - } - read_sequnlock_excl(&vnode->cb_lock); + } while (need_seqretry(&vnode->cb_lock, seq)); + + done_seqretry(&vnode->cb_lock, seq); return valid; } @@ -616,7 +628,9 @@ int afs_validate(struct afs_vnode *vnode, struct key *key) vnode->fid.vid, vnode->fid.vnode, vnode->flags, key_serial(key)); + rcu_read_lock(); valid = afs_check_validity(vnode); + rcu_read_unlock(); if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) clear_nlink(&vnode->vfs_inode); @@ -703,6 +717,7 @@ int afs_drop_inode(struct inode *inode) */ void afs_evict_inode(struct inode *inode) { + struct afs_cb_interest *cbi; struct afs_vnode *vnode; vnode = AFS_FS_I(inode); @@ -719,10 +734,14 @@ void afs_evict_inode(struct inode *inode) truncate_inode_pages_final(&inode->i_data); clear_inode(inode); - if (vnode->cb_interest) { - afs_put_cb_interest(afs_i2net(inode), vnode->cb_interest); - vnode->cb_interest = NULL; + write_seqlock(&vnode->cb_lock); + cbi = rcu_dereference_protected(vnode->cb_interest, + lockdep_is_held(&vnode->cb_lock.lock)); + if (cbi) { + afs_put_cb_interest(afs_i2net(inode), cbi); + rcu_assign_pointer(vnode->cb_interest, NULL); } + write_sequnlock(&vnode->cb_lock); while (!list_empty(&vnode->wb_keys)) { struct afs_wb_key *wbk = list_entry(vnode->wb_keys.next, -- cgit v1.2.3