| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> |
| */ |
| |
| /* |
| * fsnotify inode mark locking/lifetime/and refcnting |
| * |
| * REFCNT: |
| * The group->recnt and mark->refcnt tell how many "things" in the kernel |
| * currently are referencing the objects. Both kind of objects typically will |
| * live inside the kernel with a refcnt of 2, one for its creation and one for |
| * the reference a group and a mark hold to each other. |
| * If you are holding the appropriate locks, you can take a reference and the |
| * object itself is guaranteed to survive until the reference is dropped. |
| * |
| * LOCKING: |
| * There are 3 locks involved with fsnotify inode marks and they MUST be taken |
| * in order as follows: |
| * |
| * group->mark_mutex |
| * mark->lock |
| * mark->connector->lock |
| * |
| * group->mark_mutex protects the marks_list anchored inside a given group and |
| * each mark is hooked via the g_list. It also protects the groups private |
| * data (i.e group limits). |
| |
| * mark->lock protects the marks attributes like its masks and flags. |
| * Furthermore it protects the access to a reference of the group that the mark |
| * is assigned to as well as the access to a reference of the inode/vfsmount |
| * that is being watched by the mark. |
| * |
| * mark->connector->lock protects the list of marks anchored inside an |
| * inode / vfsmount and each mark is hooked via the i_list. |
| * |
| * A list of notification marks relating to inode / mnt is contained in |
| * fsnotify_mark_connector. That structure is alive as long as there are any |
| * marks in the list and is also protected by fsnotify_mark_srcu. A mark gets |
| * detached from fsnotify_mark_connector when last reference to the mark is |
| * dropped. Thus having mark reference is enough to protect mark->connector |
| * pointer and to make sure fsnotify_mark_connector cannot disappear. Also |
| * because we remove mark from g_list before dropping mark reference associated |
| * with that, any mark found through g_list is guaranteed to have |
| * mark->connector set until we drop group->mark_mutex. |
| * |
| * LIFETIME: |
| * Inode marks survive between when they are added to an inode and when their |
| * refcnt==0. Marks are also protected by fsnotify_mark_srcu. |
| * |
| * The inode mark can be cleared for a number of different reasons including: |
| * - The inode is unlinked for the last time. (fsnotify_inode_remove) |
| * - The inode is being evicted from cache. (fsnotify_inode_delete) |
| * - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes) |
| * - Something explicitly requests that it be removed. (fsnotify_destroy_mark) |
| * - The fsnotify_group associated with the mark is going away and all such marks |
| * need to be cleaned up. (fsnotify_clear_marks_by_group) |
| * |
| * This has the very interesting property of being able to run concurrently with |
| * any (or all) other directions. |
| */ |
| |
| #include <linux/fs.h> |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/kthread.h> |
| #include <linux/module.h> |
| #include <linux/mutex.h> |
| #include <linux/slab.h> |
| #include <linux/spinlock.h> |
| #include <linux/srcu.h> |
| #include <linux/ratelimit.h> |
| |
| #include <linux/atomic.h> |
| |
| #include <linux/fsnotify_backend.h> |
| #include "fsnotify.h" |
| |
| #define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */ |
| |
| struct srcu_struct fsnotify_mark_srcu; |
| struct kmem_cache *fsnotify_mark_connector_cachep; |
| |
| static DEFINE_SPINLOCK(destroy_lock); |
| static LIST_HEAD(destroy_list); |
| static struct fsnotify_mark_connector *connector_destroy_list; |
| |
| static void fsnotify_mark_destroy_workfn(struct work_struct *work); |
| static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn); |
| |
| static void fsnotify_connector_destroy_workfn(struct work_struct *work); |
| static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn); |
| |
| void fsnotify_get_mark(struct fsnotify_mark *mark) |
| { |
| WARN_ON_ONCE(!refcount_read(&mark->refcnt)); |
| refcount_inc(&mark->refcnt); |
| } |
| |
| static fsnotify_connp_t *fsnotify_object_connp(void *obj, |
| enum fsnotify_obj_type obj_type) |
| { |
| switch (obj_type) { |
| case FSNOTIFY_OBJ_TYPE_INODE: |
| return &((struct inode *)obj)->i_fsnotify_marks; |
| case FSNOTIFY_OBJ_TYPE_VFSMOUNT: |
| return &real_mount(obj)->mnt_fsnotify_marks; |
| case FSNOTIFY_OBJ_TYPE_SB: |
| return fsnotify_sb_marks(obj); |
| default: |
| return NULL; |
| } |
| } |
| |
| static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn) |
| { |
| if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) |
| return &fsnotify_conn_inode(conn)->i_fsnotify_mask; |
| else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) |
| return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask; |
| else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) |
| return &fsnotify_conn_sb(conn)->s_fsnotify_mask; |
| return NULL; |
| } |
| |
| __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn) |
| { |
| if (WARN_ON(!fsnotify_valid_obj_type(conn->type))) |
| return 0; |
| |
| return READ_ONCE(*fsnotify_conn_mask_p(conn)); |
| } |
| |
| static void fsnotify_get_sb_watched_objects(struct super_block *sb) |
| { |
| atomic_long_inc(fsnotify_sb_watched_objects(sb)); |
| } |
| |
| static void fsnotify_put_sb_watched_objects(struct super_block *sb) |
| { |
| atomic_long_t *watched_objects = fsnotify_sb_watched_objects(sb); |
| |
| /* the superblock can go away after this decrement */ |
| if (atomic_long_dec_and_test(watched_objects)) |
| wake_up_var(watched_objects); |
| } |
| |
| static void fsnotify_get_inode_ref(struct inode *inode) |
| { |
| ihold(inode); |
| fsnotify_get_sb_watched_objects(inode->i_sb); |
| } |
| |
| static void fsnotify_put_inode_ref(struct inode *inode) |
| { |
| /* read ->i_sb before the inode can go away */ |
| struct super_block *sb = inode->i_sb; |
| |
| iput(inode); |
| fsnotify_put_sb_watched_objects(sb); |
| } |
| |
| /* |
| * Grab or drop watched objects reference depending on whether the connector |
| * is attached and has any marks attached. |
| */ |
| static void fsnotify_update_sb_watchers(struct super_block *sb, |
| struct fsnotify_mark_connector *conn) |
| { |
| struct fsnotify_sb_info *sbinfo = fsnotify_sb_info(sb); |
| bool is_watched = conn->flags & FSNOTIFY_CONN_FLAG_IS_WATCHED; |
| struct fsnotify_mark *first_mark = NULL; |
| unsigned int highest_prio = 0; |
| |
| if (conn->obj) |
| first_mark = hlist_entry_safe(conn->list.first, |
| struct fsnotify_mark, obj_list); |
| if (first_mark) |
| highest_prio = first_mark->group->priority; |
| if (WARN_ON(highest_prio >= __FSNOTIFY_PRIO_NUM)) |
| highest_prio = 0; |
| |
| /* |
| * If the highest priority of group watching this object is prio, |
| * then watched object has a reference on counters [0..prio]. |
| * Update priority >= 1 watched objects counters. |
| */ |
| for (unsigned int p = conn->prio + 1; p <= highest_prio; p++) |
| atomic_long_inc(&sbinfo->watched_objects[p]); |
| for (unsigned int p = conn->prio; p > highest_prio; p--) |
| atomic_long_dec(&sbinfo->watched_objects[p]); |
| conn->prio = highest_prio; |
| |
| /* Update priority >= 0 (a.k.a total) watched objects counter */ |
| BUILD_BUG_ON(FSNOTIFY_PRIO_NORMAL != 0); |
| if (first_mark && !is_watched) { |
| conn->flags |= FSNOTIFY_CONN_FLAG_IS_WATCHED; |
| fsnotify_get_sb_watched_objects(sb); |
| } else if (!first_mark && is_watched) { |
| conn->flags &= ~FSNOTIFY_CONN_FLAG_IS_WATCHED; |
| fsnotify_put_sb_watched_objects(sb); |
| } |
| } |
| |
| /* |
| * Grab or drop inode reference for the connector if needed. |
| * |
| * When it's time to drop the reference, we only clear the HAS_IREF flag and |
| * return the inode object. fsnotify_drop_object() will be resonsible for doing |
| * iput() outside of spinlocks. This happens when last mark that wanted iref is |
| * detached. |
| */ |
| static struct inode *fsnotify_update_iref(struct fsnotify_mark_connector *conn, |
| bool want_iref) |
| { |
| bool has_iref = conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF; |
| struct inode *inode = NULL; |
| |
| if (conn->type != FSNOTIFY_OBJ_TYPE_INODE || |
| want_iref == has_iref) |
| return NULL; |
| |
| if (want_iref) { |
| /* Pin inode if any mark wants inode refcount held */ |
| fsnotify_get_inode_ref(fsnotify_conn_inode(conn)); |
| conn->flags |= FSNOTIFY_CONN_FLAG_HAS_IREF; |
| } else { |
| /* Unpin inode after detach of last mark that wanted iref */ |
| inode = fsnotify_conn_inode(conn); |
| conn->flags &= ~FSNOTIFY_CONN_FLAG_HAS_IREF; |
| } |
| |
| return inode; |
| } |
| |
| static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) |
| { |
| u32 new_mask = 0; |
| bool want_iref = false; |
| struct fsnotify_mark *mark; |
| |
| assert_spin_locked(&conn->lock); |
| /* We can get detached connector here when inode is getting unlinked. */ |
| if (!fsnotify_valid_obj_type(conn->type)) |
| return NULL; |
| hlist_for_each_entry(mark, &conn->list, obj_list) { |
| if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) |
| continue; |
| new_mask |= fsnotify_calc_mask(mark); |
| if (conn->type == FSNOTIFY_OBJ_TYPE_INODE && |
| !(mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)) |
| want_iref = true; |
| } |
| /* |
| * We use WRITE_ONCE() to prevent silly compiler optimizations from |
| * confusing readers not holding conn->lock with partial updates. |
| */ |
| WRITE_ONCE(*fsnotify_conn_mask_p(conn), new_mask); |
| |
| return fsnotify_update_iref(conn, want_iref); |
| } |
| |
| static bool fsnotify_conn_watches_children( |
| struct fsnotify_mark_connector *conn) |
| { |
| if (conn->type != FSNOTIFY_OBJ_TYPE_INODE) |
| return false; |
| |
| return fsnotify_inode_watches_children(fsnotify_conn_inode(conn)); |
| } |
| |
| static void fsnotify_conn_set_children_dentry_flags( |
| struct fsnotify_mark_connector *conn) |
| { |
| if (conn->type != FSNOTIFY_OBJ_TYPE_INODE) |
| return; |
| |
| fsnotify_set_children_dentry_flags(fsnotify_conn_inode(conn)); |
| } |
| |
| /* |
| * Calculate mask of events for a list of marks. The caller must make sure |
| * connector and connector->obj cannot disappear under us. Callers achieve |
| * this by holding a mark->lock or mark->group->mark_mutex for a mark on this |
| * list. |
| */ |
| void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn) |
| { |
| bool update_children; |
| |
| if (!conn) |
| return; |
| |
| spin_lock(&conn->lock); |
| update_children = !fsnotify_conn_watches_children(conn); |
| __fsnotify_recalc_mask(conn); |
| update_children &= fsnotify_conn_watches_children(conn); |
| spin_unlock(&conn->lock); |
| /* |
| * Set children's PARENT_WATCHED flags only if parent started watching. |
| * When parent stops watching, we clear false positive PARENT_WATCHED |
| * flags lazily in __fsnotify_parent(). |
| */ |
| if (update_children) |
| fsnotify_conn_set_children_dentry_flags(conn); |
| } |
| |
| /* Free all connectors queued for freeing once SRCU period ends */ |
| static void fsnotify_connector_destroy_workfn(struct work_struct *work) |
| { |
| struct fsnotify_mark_connector *conn, *free; |
| |
| spin_lock(&destroy_lock); |
| conn = connector_destroy_list; |
| connector_destroy_list = NULL; |
| spin_unlock(&destroy_lock); |
| |
| synchronize_srcu(&fsnotify_mark_srcu); |
| while (conn) { |
| free = conn; |
| conn = conn->destroy_next; |
| kmem_cache_free(fsnotify_mark_connector_cachep, free); |
| } |
| } |
| |
| static void *fsnotify_detach_connector_from_object( |
| struct fsnotify_mark_connector *conn, |
| unsigned int *type) |
| { |
| fsnotify_connp_t *connp = fsnotify_object_connp(conn->obj, conn->type); |
| struct super_block *sb = fsnotify_connector_sb(conn); |
| struct inode *inode = NULL; |
| |
| *type = conn->type; |
| if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) |
| return NULL; |
| |
| if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) { |
| inode = fsnotify_conn_inode(conn); |
| inode->i_fsnotify_mask = 0; |
| |
| /* Unpin inode when detaching from connector */ |
| if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF)) |
| inode = NULL; |
| } else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) { |
| fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0; |
| } else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) { |
| fsnotify_conn_sb(conn)->s_fsnotify_mask = 0; |
| } |
| |
| rcu_assign_pointer(*connp, NULL); |
| conn->obj = NULL; |
| conn->type = FSNOTIFY_OBJ_TYPE_DETACHED; |
| fsnotify_update_sb_watchers(sb, conn); |
| |
| return inode; |
| } |
| |
| static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark) |
| { |
| struct fsnotify_group *group = mark->group; |
| |
| if (WARN_ON_ONCE(!group)) |
| return; |
| group->ops->free_mark(mark); |
| fsnotify_put_group(group); |
| } |
| |
| /* Drop object reference originally held by a connector */ |
| static void fsnotify_drop_object(unsigned int type, void *objp) |
| { |
| if (!objp) |
| return; |
| /* Currently only inode references are passed to be dropped */ |
| if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE)) |
| return; |
| fsnotify_put_inode_ref(objp); |
| } |
| |
| void fsnotify_put_mark(struct fsnotify_mark *mark) |
| { |
| struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector); |
| void *objp = NULL; |
| unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED; |
| bool free_conn = false; |
| |
| /* Catch marks that were actually never attached to object */ |
| if (!conn) { |
| if (refcount_dec_and_test(&mark->refcnt)) |
| fsnotify_final_mark_destroy(mark); |
| return; |
| } |
| |
| /* |
| * We have to be careful so that traversals of obj_list under lock can |
| * safely grab mark reference. |
| */ |
| if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock)) |
| return; |
| |
| hlist_del_init_rcu(&mark->obj_list); |
| if (hlist_empty(&conn->list)) { |
| objp = fsnotify_detach_connector_from_object(conn, &type); |
| free_conn = true; |
| } else { |
| struct super_block *sb = fsnotify_connector_sb(conn); |
| |
| /* Update watched objects after detaching mark */ |
| if (sb) |
| fsnotify_update_sb_watchers(sb, conn); |
| objp = __fsnotify_recalc_mask(conn); |
| type = conn->type; |
| } |
| WRITE_ONCE(mark->connector, NULL); |
| spin_unlock(&conn->lock); |
| |
| fsnotify_drop_object(type, objp); |
| |
| if (free_conn) { |
| spin_lock(&destroy_lock); |
| conn->destroy_next = connector_destroy_list; |
| connector_destroy_list = conn; |
| spin_unlock(&destroy_lock); |
| queue_work(system_unbound_wq, &connector_reaper_work); |
| } |
| /* |
| * Note that we didn't update flags telling whether inode cares about |
| * what's happening with children. We update these flags from |
| * __fsnotify_parent() lazily when next event happens on one of our |
| * children. |
| */ |
| spin_lock(&destroy_lock); |
| list_add(&mark->g_list, &destroy_list); |
| spin_unlock(&destroy_lock); |
| queue_delayed_work(system_unbound_wq, &reaper_work, |
| FSNOTIFY_REAPER_DELAY); |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_put_mark); |
| |
| /* |
| * Get mark reference when we found the mark via lockless traversal of object |
| * list. Mark can be already removed from the list by now and on its way to be |
| * destroyed once SRCU period ends. |
| * |
| * Also pin the group so it doesn't disappear under us. |
| */ |
| static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark) |
| { |
| if (!mark) |
| return true; |
| |
| if (refcount_inc_not_zero(&mark->refcnt)) { |
| spin_lock(&mark->lock); |
| if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) { |
| /* mark is attached, group is still alive then */ |
| atomic_inc(&mark->group->user_waits); |
| spin_unlock(&mark->lock); |
| return true; |
| } |
| spin_unlock(&mark->lock); |
| fsnotify_put_mark(mark); |
| } |
| return false; |
| } |
| |
| /* |
| * Puts marks and wakes up group destruction if necessary. |
| * |
| * Pairs with fsnotify_get_mark_safe() |
| */ |
| static void fsnotify_put_mark_wake(struct fsnotify_mark *mark) |
| { |
| if (mark) { |
| struct fsnotify_group *group = mark->group; |
| |
| fsnotify_put_mark(mark); |
| /* |
| * We abuse notification_waitq on group shutdown for waiting for |
| * all marks pinned when waiting for userspace. |
| */ |
| if (atomic_dec_and_test(&group->user_waits) && group->shutdown) |
| wake_up(&group->notification_waitq); |
| } |
| } |
| |
| bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info) |
| __releases(&fsnotify_mark_srcu) |
| { |
| int type; |
| |
| fsnotify_foreach_iter_type(type) { |
| /* This can fail if mark is being removed */ |
| if (!fsnotify_get_mark_safe(iter_info->marks[type])) { |
| __release(&fsnotify_mark_srcu); |
| goto fail; |
| } |
| } |
| |
| /* |
| * Now that both marks are pinned by refcount in the inode / vfsmount |
| * lists, we can drop SRCU lock, and safely resume the list iteration |
| * once userspace returns. |
| */ |
| srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx); |
| |
| return true; |
| |
| fail: |
| for (type--; type >= 0; type--) |
| fsnotify_put_mark_wake(iter_info->marks[type]); |
| return false; |
| } |
| |
| void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info) |
| __acquires(&fsnotify_mark_srcu) |
| { |
| int type; |
| |
| iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); |
| fsnotify_foreach_iter_type(type) |
| fsnotify_put_mark_wake(iter_info->marks[type]); |
| } |
| |
| /* |
| * Mark mark as detached, remove it from group list. Mark still stays in object |
| * list until its last reference is dropped. Note that we rely on mark being |
| * removed from group list before corresponding reference to it is dropped. In |
| * particular we rely on mark->connector being valid while we hold |
| * group->mark_mutex if we found the mark through g_list. |
| * |
| * Must be called with group->mark_mutex held. The caller must either hold |
| * reference to the mark or be protected by fsnotify_mark_srcu. |
| */ |
| void fsnotify_detach_mark(struct fsnotify_mark *mark) |
| { |
| fsnotify_group_assert_locked(mark->group); |
| WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) && |
| refcount_read(&mark->refcnt) < 1 + |
| !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)); |
| |
| spin_lock(&mark->lock); |
| /* something else already called this function on this mark */ |
| if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) { |
| spin_unlock(&mark->lock); |
| return; |
| } |
| mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED; |
| list_del_init(&mark->g_list); |
| spin_unlock(&mark->lock); |
| |
| /* Drop mark reference acquired in fsnotify_add_mark_locked() */ |
| fsnotify_put_mark(mark); |
| } |
| |
| /* |
| * Free fsnotify mark. The mark is actually only marked as being freed. The |
| * freeing is actually happening only once last reference to the mark is |
| * dropped from a workqueue which first waits for srcu period end. |
| * |
| * Caller must have a reference to the mark or be protected by |
| * fsnotify_mark_srcu. |
| */ |
| void fsnotify_free_mark(struct fsnotify_mark *mark) |
| { |
| struct fsnotify_group *group = mark->group; |
| |
| spin_lock(&mark->lock); |
| /* something else already called this function on this mark */ |
| if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) { |
| spin_unlock(&mark->lock); |
| return; |
| } |
| mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE; |
| spin_unlock(&mark->lock); |
| |
| /* |
| * Some groups like to know that marks are being freed. This is a |
| * callback to the group function to let it know that this mark |
| * is being freed. |
| */ |
| if (group->ops->freeing_mark) |
| group->ops->freeing_mark(mark, group); |
| } |
| |
| void fsnotify_destroy_mark(struct fsnotify_mark *mark, |
| struct fsnotify_group *group) |
| { |
| fsnotify_group_lock(group); |
| fsnotify_detach_mark(mark); |
| fsnotify_group_unlock(group); |
| fsnotify_free_mark(mark); |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_destroy_mark); |
| |
| /* |
| * Sorting function for lists of fsnotify marks. |
| * |
| * Fanotify supports different notification classes (reflected as priority of |
| * notification group). Events shall be passed to notification groups in |
| * decreasing priority order. To achieve this marks in notification lists for |
| * inodes and vfsmounts are sorted so that priorities of corresponding groups |
| * are descending. |
| * |
| * Furthermore correct handling of the ignore mask requires processing inode |
| * and vfsmount marks of each group together. Using the group address as |
| * further sort criterion provides a unique sorting order and thus we can |
| * merge inode and vfsmount lists of marks in linear time and find groups |
| * present in both lists. |
| * |
| * A return value of 1 signifies that b has priority over a. |
| * A return value of 0 signifies that the two marks have to be handled together. |
| * A return value of -1 signifies that a has priority over b. |
| */ |
| int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b) |
| { |
| if (a == b) |
| return 0; |
| if (!a) |
| return 1; |
| if (!b) |
| return -1; |
| if (a->priority < b->priority) |
| return 1; |
| if (a->priority > b->priority) |
| return -1; |
| if (a < b) |
| return 1; |
| return -1; |
| } |
| |
| static int fsnotify_attach_info_to_sb(struct super_block *sb) |
| { |
| struct fsnotify_sb_info *sbinfo; |
| |
| /* sb info is freed on fsnotify_sb_delete() */ |
| sbinfo = kzalloc(sizeof(*sbinfo), GFP_KERNEL); |
| if (!sbinfo) |
| return -ENOMEM; |
| |
| /* |
| * cmpxchg() provides the barrier so that callers of fsnotify_sb_info() |
| * will observe an initialized structure |
| */ |
| if (cmpxchg(&sb->s_fsnotify_info, NULL, sbinfo)) { |
| /* Someone else created sbinfo for us */ |
| kfree(sbinfo); |
| } |
| return 0; |
| } |
| |
| static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp, |
| void *obj, unsigned int obj_type) |
| { |
| struct fsnotify_mark_connector *conn; |
| |
| conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL); |
| if (!conn) |
| return -ENOMEM; |
| spin_lock_init(&conn->lock); |
| INIT_HLIST_HEAD(&conn->list); |
| conn->flags = 0; |
| conn->prio = 0; |
| conn->type = obj_type; |
| conn->obj = obj; |
| |
| /* |
| * cmpxchg() provides the barrier so that readers of *connp can see |
| * only initialized structure |
| */ |
| if (cmpxchg(connp, NULL, conn)) { |
| /* Someone else created list structure for us */ |
| kmem_cache_free(fsnotify_mark_connector_cachep, conn); |
| } |
| return 0; |
| } |
| |
| /* |
| * Get mark connector, make sure it is alive and return with its lock held. |
| * This is for users that get connector pointer from inode or mount. Users that |
| * hold reference to a mark on the list may directly lock connector->lock as |
| * they are sure list cannot go away under them. |
| */ |
| static struct fsnotify_mark_connector *fsnotify_grab_connector( |
| fsnotify_connp_t *connp) |
| { |
| struct fsnotify_mark_connector *conn; |
| int idx; |
| |
| idx = srcu_read_lock(&fsnotify_mark_srcu); |
| conn = srcu_dereference(*connp, &fsnotify_mark_srcu); |
| if (!conn) |
| goto out; |
| spin_lock(&conn->lock); |
| if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) { |
| spin_unlock(&conn->lock); |
| srcu_read_unlock(&fsnotify_mark_srcu, idx); |
| return NULL; |
| } |
| out: |
| srcu_read_unlock(&fsnotify_mark_srcu, idx); |
| return conn; |
| } |
| |
| /* |
| * Add mark into proper place in given list of marks. These marks may be used |
| * for the fsnotify backend to determine which event types should be delivered |
| * to which group and for which inodes. These marks are ordered according to |
| * priority, highest number first, and then by the group's location in memory. |
| */ |
| static int fsnotify_add_mark_list(struct fsnotify_mark *mark, void *obj, |
| unsigned int obj_type, int add_flags) |
| { |
| struct super_block *sb = fsnotify_object_sb(obj, obj_type); |
| struct fsnotify_mark *lmark, *last = NULL; |
| struct fsnotify_mark_connector *conn; |
| fsnotify_connp_t *connp; |
| int cmp; |
| int err = 0; |
| |
| if (WARN_ON(!fsnotify_valid_obj_type(obj_type))) |
| return -EINVAL; |
| |
| /* |
| * Attach the sb info before attaching a connector to any object on sb. |
| * The sb info will remain attached as long as sb lives. |
| */ |
| if (!fsnotify_sb_info(sb)) { |
| err = fsnotify_attach_info_to_sb(sb); |
| if (err) |
| return err; |
| } |
| |
| connp = fsnotify_object_connp(obj, obj_type); |
| restart: |
| spin_lock(&mark->lock); |
| conn = fsnotify_grab_connector(connp); |
| if (!conn) { |
| spin_unlock(&mark->lock); |
| err = fsnotify_attach_connector_to_object(connp, obj, obj_type); |
| if (err) |
| return err; |
| goto restart; |
| } |
| |
| /* is mark the first mark? */ |
| if (hlist_empty(&conn->list)) { |
| hlist_add_head_rcu(&mark->obj_list, &conn->list); |
| goto added; |
| } |
| |
| /* should mark be in the middle of the current list? */ |
| hlist_for_each_entry(lmark, &conn->list, obj_list) { |
| last = lmark; |
| |
| if ((lmark->group == mark->group) && |
| (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) && |
| !(mark->group->flags & FSNOTIFY_GROUP_DUPS)) { |
| err = -EEXIST; |
| goto out_err; |
| } |
| |
| cmp = fsnotify_compare_groups(lmark->group, mark->group); |
| if (cmp >= 0) { |
| hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list); |
| goto added; |
| } |
| } |
| |
| BUG_ON(last == NULL); |
| /* mark should be the last entry. last is the current last entry */ |
| hlist_add_behind_rcu(&mark->obj_list, &last->obj_list); |
| added: |
| fsnotify_update_sb_watchers(sb, conn); |
| /* |
| * Since connector is attached to object using cmpxchg() we are |
| * guaranteed that connector initialization is fully visible by anyone |
| * seeing mark->connector set. |
| */ |
| WRITE_ONCE(mark->connector, conn); |
| out_err: |
| spin_unlock(&conn->lock); |
| spin_unlock(&mark->lock); |
| return err; |
| } |
| |
| /* |
| * Attach an initialized mark to a given group and fs object. |
| * These marks may be used for the fsnotify backend to determine which |
| * event types should be delivered to which group. |
| */ |
| int fsnotify_add_mark_locked(struct fsnotify_mark *mark, |
| void *obj, unsigned int obj_type, |
| int add_flags) |
| { |
| struct fsnotify_group *group = mark->group; |
| int ret = 0; |
| |
| fsnotify_group_assert_locked(group); |
| |
| /* |
| * LOCKING ORDER!!!! |
| * group->mark_mutex |
| * mark->lock |
| * mark->connector->lock |
| */ |
| spin_lock(&mark->lock); |
| mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED; |
| |
| list_add(&mark->g_list, &group->marks_list); |
| fsnotify_get_mark(mark); /* for g_list */ |
| spin_unlock(&mark->lock); |
| |
| ret = fsnotify_add_mark_list(mark, obj, obj_type, add_flags); |
| if (ret) |
| goto err; |
| |
| fsnotify_recalc_mask(mark->connector); |
| |
| return ret; |
| err: |
| spin_lock(&mark->lock); |
| mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE | |
| FSNOTIFY_MARK_FLAG_ATTACHED); |
| list_del_init(&mark->g_list); |
| spin_unlock(&mark->lock); |
| |
| fsnotify_put_mark(mark); |
| return ret; |
| } |
| |
| int fsnotify_add_mark(struct fsnotify_mark *mark, void *obj, |
| unsigned int obj_type, int add_flags) |
| { |
| int ret; |
| struct fsnotify_group *group = mark->group; |
| |
| fsnotify_group_lock(group); |
| ret = fsnotify_add_mark_locked(mark, obj, obj_type, add_flags); |
| fsnotify_group_unlock(group); |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_add_mark); |
| |
| /* |
| * Given a list of marks, find the mark associated with given group. If found |
| * take a reference to that mark and return it, else return NULL. |
| */ |
| struct fsnotify_mark *fsnotify_find_mark(void *obj, unsigned int obj_type, |
| struct fsnotify_group *group) |
| { |
| fsnotify_connp_t *connp = fsnotify_object_connp(obj, obj_type); |
| struct fsnotify_mark_connector *conn; |
| struct fsnotify_mark *mark; |
| |
| if (!connp) |
| return NULL; |
| |
| conn = fsnotify_grab_connector(connp); |
| if (!conn) |
| return NULL; |
| |
| hlist_for_each_entry(mark, &conn->list, obj_list) { |
| if (mark->group == group && |
| (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) { |
| fsnotify_get_mark(mark); |
| spin_unlock(&conn->lock); |
| return mark; |
| } |
| } |
| spin_unlock(&conn->lock); |
| return NULL; |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_find_mark); |
| |
| /* Clear any marks in a group with given type mask */ |
| void fsnotify_clear_marks_by_group(struct fsnotify_group *group, |
| unsigned int obj_type) |
| { |
| struct fsnotify_mark *lmark, *mark; |
| LIST_HEAD(to_free); |
| struct list_head *head = &to_free; |
| |
| /* Skip selection step if we want to clear all marks. */ |
| if (obj_type == FSNOTIFY_OBJ_TYPE_ANY) { |
| head = &group->marks_list; |
| goto clear; |
| } |
| /* |
| * We have to be really careful here. Anytime we drop mark_mutex, e.g. |
| * fsnotify_clear_marks_by_inode() can come and free marks. Even in our |
| * to_free list so we have to use mark_mutex even when accessing that |
| * list. And freeing mark requires us to drop mark_mutex. So we can |
| * reliably free only the first mark in the list. That's why we first |
| * move marks to free to to_free list in one go and then free marks in |
| * to_free list one by one. |
| */ |
| fsnotify_group_lock(group); |
| list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) { |
| if (mark->connector->type == obj_type) |
| list_move(&mark->g_list, &to_free); |
| } |
| fsnotify_group_unlock(group); |
| |
| clear: |
| while (1) { |
| fsnotify_group_lock(group); |
| if (list_empty(head)) { |
| fsnotify_group_unlock(group); |
| break; |
| } |
| mark = list_first_entry(head, struct fsnotify_mark, g_list); |
| fsnotify_get_mark(mark); |
| fsnotify_detach_mark(mark); |
| fsnotify_group_unlock(group); |
| fsnotify_free_mark(mark); |
| fsnotify_put_mark(mark); |
| } |
| } |
| |
| /* Destroy all marks attached to an object via connector */ |
| void fsnotify_destroy_marks(fsnotify_connp_t *connp) |
| { |
| struct fsnotify_mark_connector *conn; |
| struct fsnotify_mark *mark, *old_mark = NULL; |
| void *objp; |
| unsigned int type; |
| |
| conn = fsnotify_grab_connector(connp); |
| if (!conn) |
| return; |
| /* |
| * We have to be careful since we can race with e.g. |
| * fsnotify_clear_marks_by_group() and once we drop the conn->lock, the |
| * list can get modified. However we are holding mark reference and |
| * thus our mark cannot be removed from obj_list so we can continue |
| * iteration after regaining conn->lock. |
| */ |
| hlist_for_each_entry(mark, &conn->list, obj_list) { |
| fsnotify_get_mark(mark); |
| spin_unlock(&conn->lock); |
| if (old_mark) |
| fsnotify_put_mark(old_mark); |
| old_mark = mark; |
| fsnotify_destroy_mark(mark, mark->group); |
| spin_lock(&conn->lock); |
| } |
| /* |
| * Detach list from object now so that we don't pin inode until all |
| * mark references get dropped. It would lead to strange results such |
| * as delaying inode deletion or blocking unmount. |
| */ |
| objp = fsnotify_detach_connector_from_object(conn, &type); |
| spin_unlock(&conn->lock); |
| if (old_mark) |
| fsnotify_put_mark(old_mark); |
| fsnotify_drop_object(type, objp); |
| } |
| |
| /* |
| * Nothing fancy, just initialize lists and locks and counters. |
| */ |
| void fsnotify_init_mark(struct fsnotify_mark *mark, |
| struct fsnotify_group *group) |
| { |
| memset(mark, 0, sizeof(*mark)); |
| spin_lock_init(&mark->lock); |
| refcount_set(&mark->refcnt, 1); |
| fsnotify_get_group(group); |
| mark->group = group; |
| WRITE_ONCE(mark->connector, NULL); |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_init_mark); |
| |
| /* |
| * Destroy all marks in destroy_list, waits for SRCU period to finish before |
| * actually freeing marks. |
| */ |
| static void fsnotify_mark_destroy_workfn(struct work_struct *work) |
| { |
| struct fsnotify_mark *mark, *next; |
| struct list_head private_destroy_list; |
| |
| spin_lock(&destroy_lock); |
| /* exchange the list head */ |
| list_replace_init(&destroy_list, &private_destroy_list); |
| spin_unlock(&destroy_lock); |
| |
| synchronize_srcu(&fsnotify_mark_srcu); |
| |
| list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) { |
| list_del_init(&mark->g_list); |
| fsnotify_final_mark_destroy(mark); |
| } |
| } |
| |
| /* Wait for all marks queued for destruction to be actually destroyed */ |
| void fsnotify_wait_marks_destroyed(void) |
| { |
| flush_delayed_work(&reaper_work); |
| } |
| EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed); |