diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 177 |
1 files changed, 111 insertions, 66 deletions
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 <linux/syscalls.h> #include <linux/slab.h> #include <linux/sched.h> +#include <linux/spinlock.h> +#include <linux/percpu.h> #include <linux/smp_lock.h> #include <linux/init.h> #include <linux/kernel.h> @@ -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); |