From b04f784e5d19ed58892833dae845738972cea260 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 18 Aug 2010 04:37:34 +1000 Subject: fs: remove extra lookup in __lookup_hash fs: remove extra lookup in __lookup_hash Optimize lookup for create operations, where no dentry should often be common-case. In cases where it is not, such as unlink, the added overhead is much smaller than the removed. Also, move comments about __d_lookup racyness to the __d_lookup call site. d_lookup is intuitive; __d_lookup is what needs commenting. So in that same vein, add kerneldoc comments to __d_lookup and clean up some of the comments: - We are interested in how the RCU lookup works here, particularly with renames. Make that explicit, and point to the document where it is explained in more detail. - RCU is pretty standard now, and macros make implementations pretty mindless. If we want to know about RCU barrier details, we look in RCU code. - Delete some boring legacy comments because we don't care much about how the code used to work, more about the interesting parts of how it works now. So comments about lazy LRU may be interesting, but would better be done in the LRU or refcount management code. Signed-off-by: Nick Piggin Signed-off-by: Al Viro --- fs/dcache.c | 60 +++++++++++++++++++++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 25 deletions(-) (limited to 'fs/dcache.c') diff --git a/fs/dcache.c b/fs/dcache.c index 4d13bf50b7b1..d56a40b5a577 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1332,31 +1332,13 @@ EXPORT_SYMBOL(d_add_ci); * d_lookup - search for a dentry * @parent: parent dentry * @name: qstr of name we wish to find + * Returns: dentry, or NULL * - * Searches the children of the parent dentry for the name in question. If - * the dentry is found its reference count is incremented and the dentry - * is returned. The caller must use dput to free the entry when it has - * finished using it. %NULL is returned on failure. - * - * __d_lookup is dcache_lock free. The hash list is protected using RCU. - * Memory barriers are used while updating and doing lockless traversal. - * To avoid races with d_move while rename is happening, d_lock is used. - * - * Overflows in memcmp(), while d_move, are avoided by keeping the length - * and name pointer in one structure pointed by d_qstr. - * - * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while - * lookup is going on. - * - * The dentry unused LRU is not updated even if lookup finds the required dentry - * in there. It is updated in places such as prune_dcache, shrink_dcache_sb, - * select_parent and __dget_locked. This laziness saves lookup from dcache_lock - * acquisition. - * - * d_lookup() is protected against the concurrent renames in some unrelated - * directory using the seqlockt_t rename_lock. + * d_lookup searches the children of the parent dentry for the name in + * question. If the dentry is found its reference count is incremented and the + * dentry is returned. The caller must use dput to free the entry when it has + * finished using it. %NULL is returned if the dentry does not exist. */ - struct dentry * d_lookup(struct dentry * parent, struct qstr * name) { struct dentry * dentry = NULL; @@ -1372,6 +1354,21 @@ struct dentry * d_lookup(struct dentry * parent, struct qstr * name) } EXPORT_SYMBOL(d_lookup); +/* + * __d_lookup - search for a dentry (racy) + * @parent: parent dentry + * @name: qstr of name we wish to find + * Returns: dentry, or NULL + * + * __d_lookup is like d_lookup, however it may (rarely) return a + * false-negative result due to unrelated rename activity. + * + * __d_lookup is slightly faster by avoiding rename_lock read seqlock, + * however it must be used carefully, eg. with a following d_lookup in + * the case of failure. + * + * __d_lookup callers must be commented. + */ struct dentry * __d_lookup(struct dentry * parent, struct qstr * name) { unsigned int len = name->len; @@ -1382,6 +1379,19 @@ struct dentry * __d_lookup(struct dentry * parent, struct qstr * name) struct hlist_node *node; struct dentry *dentry; + /* + * The hash list is protected using RCU. + * + * Take d_lock when comparing a candidate dentry, to avoid races + * with d_move(). + * + * It is possible that concurrent renames can mess up our list + * walk here and result in missing our dentry, resulting in the + * false-negative result. d_lookup() protects against concurrent + * renames using rename_lock seqlock. + * + * See Documentation/vfs/dcache-locking.txt for more details. + */ rcu_read_lock(); hlist_for_each_entry_rcu(dentry, node, head, d_hash) { @@ -1396,8 +1406,8 @@ struct dentry * __d_lookup(struct dentry * parent, struct qstr * name) /* * Recheck the dentry after taking the lock - d_move may have - * changed things. Don't bother checking the hash because we're - * about to compare the whole name anyway. + * changed things. Don't bother checking the hash because + * we're about to compare the whole name anyway. */ if (dentry->d_parent != parent) goto next; -- cgit v1.2.3-58-ga151 From 99b7db7b8ffd6bb755eb0a175596421a0b581cb2 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 18 Aug 2010 04:37:39 +1000 Subject: fs: brlock vfsmount_lock fs: brlock vfsmount_lock Use a brlock for the vfsmount lock. It must be taken for write whenever modifying the mount hash or associated fields, and may be taken for read when performing mount hash lookups. A new lock is added for the mnt-id allocator, so it doesn't need to take the heavy vfsmount write-lock. The number of atomics should remain the same for fastpath rlock cases, though code would be slightly slower due to per-cpu access. Scalability is not not be much improved in common cases yet, due to other locks (ie. dcache_lock) getting in the way. However path lookups crossing mountpoints should be one case where scalability is improved (currently requiring the global lock). The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node Altix system (high latency to remote nodes), a simple umount microbenchmark (mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it took 6.8s, afterwards took 7.1s, about 5% slower. Cc: Al Viro Signed-off-by: Nick Piggin Signed-off-by: Al Viro --- fs/dcache.c | 11 ++-- fs/internal.h | 5 +- fs/namei.c | 7 ++- fs/namespace.c | 177 ++++++++++++++++++++++++++++++++++++--------------------- fs/pnode.c | 11 +++- 5 files changed, 134 insertions(+), 77 deletions(-) (limited to 'fs/dcache.c') diff --git a/fs/dcache.c b/fs/dcache.c index d56a40b5a577..83293be48149 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1935,7 +1935,7 @@ static int prepend_path(const struct path *path, struct path *root, bool slash = false; int error = 0; - spin_lock(&vfsmount_lock); + br_read_lock(vfsmount_lock); while (dentry != root->dentry || vfsmnt != root->mnt) { struct dentry * parent; @@ -1964,7 +1964,7 @@ out: if (!error && !slash) error = prepend(buffer, buflen, "/", 1); - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return error; global_root: @@ -2302,11 +2302,12 @@ int path_is_under(struct path *path1, struct path *path2) struct vfsmount *mnt = path1->mnt; struct dentry *dentry = path1->dentry; int res; - spin_lock(&vfsmount_lock); + + br_read_lock(vfsmount_lock); if (mnt != path2->mnt) { for (;;) { if (mnt->mnt_parent == mnt) { - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return 0; } if (mnt->mnt_parent == path2->mnt) @@ -2316,7 +2317,7 @@ int path_is_under(struct path *path1, struct path *path2) dentry = mnt->mnt_mountpoint; } res = is_subdir(dentry, path2->dentry); - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return res; } EXPORT_SYMBOL(path_is_under); diff --git a/fs/internal.h b/fs/internal.h index 6a5c13a80660..a6910e91cee8 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -9,6 +9,8 @@ * 2 of the License, or (at your option) any later version. */ +#include + struct super_block; struct linux_binprm; struct path; @@ -70,7 +72,8 @@ extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int); extern void __init mnt_init(void); -extern spinlock_t vfsmount_lock; +DECLARE_BRLOCK(vfsmount_lock); + /* * fs_struct.c diff --git a/fs/namei.c b/fs/namei.c index 11de7c39ff76..24896e833565 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -595,15 +595,16 @@ int follow_up(struct path *path) { struct vfsmount *parent; struct dentry *mountpoint; - spin_lock(&vfsmount_lock); + + br_read_lock(vfsmount_lock); parent = path->mnt->mnt_parent; if (parent == path->mnt) { - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return 0; } mntget(parent); mountpoint = dget(path->mnt->mnt_mountpoint); - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); dput(path->dentry); path->dentry = mountpoint; mntput(path->mnt); diff --git a/fs/namespace.c b/fs/namespace.c index 2e10cb19c5b0..de402eb6eafb 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -11,6 +11,8 @@ #include #include #include +#include +#include #include #include #include @@ -38,12 +40,10 @@ #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) #define HASH_SIZE (1UL << HASH_SHIFT) -/* spinlock for vfsmount related operations, inplace of dcache_lock */ -__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); - static int event; static DEFINE_IDA(mnt_id_ida); static DEFINE_IDA(mnt_group_ida); +static DEFINE_SPINLOCK(mnt_id_lock); static int mnt_id_start = 0; static int mnt_group_start = 1; @@ -55,6 +55,16 @@ static struct rw_semaphore namespace_sem; struct kobject *fs_kobj; EXPORT_SYMBOL_GPL(fs_kobj); +/* + * vfsmount lock may be taken for read to prevent changes to the + * vfsmount hash, ie. during mountpoint lookups or walking back + * up the tree. + * + * It should be taken for write in all cases where the vfsmount + * tree or hash is modified or when a vfsmount structure is modified. + */ +DEFINE_BRLOCK(vfsmount_lock); + static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); @@ -65,18 +75,21 @@ static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) -/* allocation is serialized by namespace_sem */ +/* + * allocation is serialized by namespace_sem, but we need the spinlock to + * serialize with freeing. + */ static int mnt_alloc_id(struct vfsmount *mnt) { int res; retry: ida_pre_get(&mnt_id_ida, GFP_KERNEL); - spin_lock(&vfsmount_lock); + spin_lock(&mnt_id_lock); res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); if (!res) mnt_id_start = mnt->mnt_id + 1; - spin_unlock(&vfsmount_lock); + spin_unlock(&mnt_id_lock); if (res == -EAGAIN) goto retry; @@ -86,11 +99,11 @@ retry: static void mnt_free_id(struct vfsmount *mnt) { int id = mnt->mnt_id; - spin_lock(&vfsmount_lock); + spin_lock(&mnt_id_lock); ida_remove(&mnt_id_ida, id); if (mnt_id_start > id) mnt_id_start = id; - spin_unlock(&vfsmount_lock); + spin_unlock(&mnt_id_lock); } /* @@ -348,7 +361,7 @@ static int mnt_make_readonly(struct vfsmount *mnt) { int ret = 0; - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); mnt->mnt_flags |= MNT_WRITE_HOLD; /* * After storing MNT_WRITE_HOLD, we'll read the counters. This store @@ -382,15 +395,15 @@ static int mnt_make_readonly(struct vfsmount *mnt) */ smp_wmb(); mnt->mnt_flags &= ~MNT_WRITE_HOLD; - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); return ret; } static void __mnt_unmake_readonly(struct vfsmount *mnt) { - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); mnt->mnt_flags &= ~MNT_READONLY; - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) @@ -414,6 +427,7 @@ void free_vfsmnt(struct vfsmount *mnt) /* * find the first or last mount at @dentry on vfsmount @mnt depending on * @dir. If @dir is set return the first mount else return the last mount. + * vfsmount_lock must be held for read or write. */ struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, int dir) @@ -443,10 +457,11 @@ struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, struct vfsmount *lookup_mnt(struct path *path) { struct vfsmount *child_mnt; - spin_lock(&vfsmount_lock); + + br_read_lock(vfsmount_lock); if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) mntget(child_mnt); - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return child_mnt; } @@ -455,6 +470,9 @@ static inline int check_mnt(struct vfsmount *mnt) return mnt->mnt_ns == current->nsproxy->mnt_ns; } +/* + * vfsmount lock must be held for write + */ static void touch_mnt_namespace(struct mnt_namespace *ns) { if (ns) { @@ -463,6 +481,9 @@ static void touch_mnt_namespace(struct mnt_namespace *ns) } } +/* + * vfsmount lock must be held for write + */ static void __touch_mnt_namespace(struct mnt_namespace *ns) { if (ns && ns->event != event) { @@ -471,6 +492,9 @@ static void __touch_mnt_namespace(struct mnt_namespace *ns) } } +/* + * vfsmount lock must be held for write + */ static void detach_mnt(struct vfsmount *mnt, struct path *old_path) { old_path->dentry = mnt->mnt_mountpoint; @@ -482,6 +506,9 @@ static void detach_mnt(struct vfsmount *mnt, struct path *old_path) old_path->dentry->d_mounted--; } +/* + * vfsmount lock must be held for write + */ void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, struct vfsmount *child_mnt) { @@ -490,6 +517,9 @@ void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, dentry->d_mounted++; } +/* + * vfsmount lock must be held for write + */ static void attach_mnt(struct vfsmount *mnt, struct path *path) { mnt_set_mountpoint(path->mnt, path->dentry, mnt); @@ -499,7 +529,7 @@ static void attach_mnt(struct vfsmount *mnt, struct path *path) } /* - * the caller must hold vfsmount_lock + * vfsmount lock must be held for write */ static void commit_tree(struct vfsmount *mnt) { @@ -623,39 +653,43 @@ static inline void __mntput(struct vfsmount *mnt) void mntput_no_expire(struct vfsmount *mnt) { repeat: - if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { - if (likely(!mnt->mnt_pinned)) { - spin_unlock(&vfsmount_lock); - __mntput(mnt); - return; - } - atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); - mnt->mnt_pinned = 0; - spin_unlock(&vfsmount_lock); - acct_auto_close_mnt(mnt); - goto repeat; + if (atomic_add_unless(&mnt->mnt_count, -1, 1)) + return; + br_write_lock(vfsmount_lock); + if (!atomic_dec_and_test(&mnt->mnt_count)) { + br_write_unlock(vfsmount_lock); + return; + } + if (likely(!mnt->mnt_pinned)) { + br_write_unlock(vfsmount_lock); + __mntput(mnt); + return; } + atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); + mnt->mnt_pinned = 0; + br_write_unlock(vfsmount_lock); + acct_auto_close_mnt(mnt); + goto repeat; } - EXPORT_SYMBOL(mntput_no_expire); void mnt_pin(struct vfsmount *mnt) { - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); mnt->mnt_pinned++; - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } EXPORT_SYMBOL(mnt_pin); void mnt_unpin(struct vfsmount *mnt) { - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); if (mnt->mnt_pinned) { atomic_inc(&mnt->mnt_count); mnt->mnt_pinned--; } - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } EXPORT_SYMBOL(mnt_unpin); @@ -746,12 +780,12 @@ int mnt_had_events(struct proc_mounts *p) struct mnt_namespace *ns = p->ns; int res = 0; - spin_lock(&vfsmount_lock); + br_read_lock(vfsmount_lock); if (p->event != ns->event) { p->event = ns->event; res = 1; } - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); return res; } @@ -952,12 +986,12 @@ int may_umount_tree(struct vfsmount *mnt) int minimum_refs = 0; struct vfsmount *p; - spin_lock(&vfsmount_lock); + br_read_lock(vfsmount_lock); for (p = mnt; p; p = next_mnt(p, mnt)) { actual_refs += atomic_read(&p->mnt_count); minimum_refs += 2; } - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); if (actual_refs > minimum_refs) return 0; @@ -984,10 +1018,10 @@ int may_umount(struct vfsmount *mnt) { int ret = 1; down_read(&namespace_sem); - spin_lock(&vfsmount_lock); + br_read_lock(vfsmount_lock); if (propagate_mount_busy(mnt, 2)) ret = 0; - spin_unlock(&vfsmount_lock); + br_read_unlock(vfsmount_lock); up_read(&namespace_sem); return ret; } @@ -1003,13 +1037,14 @@ void release_mounts(struct list_head *head) if (mnt->mnt_parent != mnt) { struct dentry *dentry; struct vfsmount *m; - spin_lock(&vfsmount_lock); + + br_write_lock(vfsmount_lock); dentry = mnt->mnt_mountpoint; m = mnt->mnt_parent; mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; m->mnt_ghosts--; - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); dput(dentry); mntput(m); } @@ -1017,6 +1052,10 @@ void release_mounts(struct list_head *head) } } +/* + * vfsmount lock must be held for write + * namespace_sem must be held for write + */ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) { struct vfsmount *p; @@ -1107,7 +1146,7 @@ static int do_umount(struct vfsmount *mnt, int flags) } down_write(&namespace_sem); - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); event++; if (!(flags & MNT_DETACH)) @@ -1119,7 +1158,7 @@ static int do_umount(struct vfsmount *mnt, int flags) umount_tree(mnt, 1, &umount_list); retval = 0; } - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); return retval; @@ -1231,19 +1270,19 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, q = clone_mnt(p, p->mnt_root, flag); if (!q) goto Enomem; - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); list_add_tail(&q->mnt_list, &res->mnt_list); attach_mnt(q, &path); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } } return res; Enomem: if (res) { LIST_HEAD(umount_list); - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); umount_tree(res, 0, &umount_list); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); release_mounts(&umount_list); } return NULL; @@ -1262,9 +1301,9 @@ void drop_collected_mounts(struct vfsmount *mnt) { LIST_HEAD(umount_list); down_write(&namespace_sem); - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); umount_tree(mnt, 0, &umount_list); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); } @@ -1392,7 +1431,7 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt, if (err) goto out_cleanup_ids; - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); if (IS_MNT_SHARED(dest_mnt)) { for (p = source_mnt; p; p = next_mnt(p, source_mnt)) @@ -1411,7 +1450,8 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt, list_del_init(&child->mnt_hash); commit_tree(child); } - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); + return 0; out_cleanup_ids: @@ -1466,10 +1506,10 @@ static int do_change_type(struct path *path, int flag) goto out_unlock; } - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) change_mnt_propagation(m, type); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); out_unlock: up_write(&namespace_sem); @@ -1513,9 +1553,10 @@ static int do_loopback(struct path *path, char *old_name, err = graft_tree(mnt, path); if (err) { LIST_HEAD(umount_list); - spin_lock(&vfsmount_lock); + + br_write_lock(vfsmount_lock); umount_tree(mnt, 0, &umount_list); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); release_mounts(&umount_list); } @@ -1568,16 +1609,16 @@ static int do_remount(struct path *path, int flags, int mnt_flags, else err = do_remount_sb(sb, flags, data, 0); if (!err) { - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK; path->mnt->mnt_flags = mnt_flags; - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } up_write(&sb->s_umount); if (!err) { - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); touch_mnt_namespace(path->mnt->mnt_ns); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); } return err; } @@ -1754,7 +1795,7 @@ void mark_mounts_for_expiry(struct list_head *mounts) return; down_write(&namespace_sem); - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); /* extract from the expiration list every vfsmount that matches the * following criteria: @@ -1773,7 +1814,7 @@ void mark_mounts_for_expiry(struct list_head *mounts) touch_mnt_namespace(mnt->mnt_ns); umount_tree(mnt, 1, &umounts); } - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); up_write(&namespace_sem); release_mounts(&umounts); @@ -1830,6 +1871,8 @@ resume: /* * process a list of expirable mountpoints with the intent of discarding any * submounts of a specific parent mountpoint + * + * vfsmount_lock must be held for write */ static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) { @@ -2048,9 +2091,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, kfree(new_ns); return ERR_PTR(-ENOMEM); } - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); list_add_tail(&new_ns->list, &new_ns->root->mnt_list); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); /* * Second pass: switch the tsk->fs->* elements and mark new vfsmounts @@ -2244,7 +2287,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, goto out2; /* not attached */ /* make sure we can reach put_old from new_root */ tmp = old.mnt; - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); if (tmp != new.mnt) { for (;;) { if (tmp->mnt_parent == tmp) @@ -2264,7 +2307,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, /* mount new_root on / */ attach_mnt(new.mnt, &root_parent); touch_mnt_namespace(current->nsproxy->mnt_ns); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); chroot_fs_refs(&root, &new); error = 0; path_put(&root_parent); @@ -2279,7 +2322,7 @@ out1: out0: return error; out3: - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); goto out2; } @@ -2326,6 +2369,8 @@ void __init mnt_init(void) for (u = 0; u < HASH_SIZE; u++) INIT_LIST_HEAD(&mount_hashtable[u]); + br_lock_init(vfsmount_lock); + err = sysfs_init(); if (err) printk(KERN_WARNING "%s: sysfs_init error: %d\n", @@ -2344,9 +2389,9 @@ void put_mnt_ns(struct mnt_namespace *ns) if (!atomic_dec_and_test(&ns->count)) return; down_write(&namespace_sem); - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); umount_tree(ns->root, 0, &umount_list); - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); kfree(ns); diff --git a/fs/pnode.c b/fs/pnode.c index 5cc564a83149..8066b8dd748f 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -126,6 +126,9 @@ static int do_make_slave(struct vfsmount *mnt) return 0; } +/* + * vfsmount lock must be held for write + */ void change_mnt_propagation(struct vfsmount *mnt, int type) { if (type == MS_SHARED) { @@ -270,12 +273,12 @@ int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry, prev_src_mnt = child; } out: - spin_lock(&vfsmount_lock); + br_write_lock(vfsmount_lock); while (!list_empty(&tmp_list)) { child = list_first_entry(&tmp_list, struct vfsmount, mnt_hash); umount_tree(child, 0, &umount_list); } - spin_unlock(&vfsmount_lock); + br_write_unlock(vfsmount_lock); release_mounts(&umount_list); return ret; } @@ -296,6 +299,8 @@ static inline int do_refcount_check(struct vfsmount *mnt, int count) * other mounts its parent propagates to. * Check if any of these mounts that **do not have submounts** * have more references than 'refcnt'. If so return busy. + * + * vfsmount lock must be held for read or write */ int propagate_mount_busy(struct vfsmount *mnt, int refcnt) { @@ -353,6 +358,8 @@ static void __propagate_umount(struct vfsmount *mnt) * collect all mounts that receive propagation from the mount in @list, * and return these additional mounts in the same list. * @list: the list of mounts to be unmounted. + * + * vfsmount lock must be held for write */ int propagate_umount(struct list_head *list) { -- cgit v1.2.3-58-ga151