diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-03-30 17:26:08 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-03-30 17:26:08 -0700 |
commit | fedc1ed0f11be666de066b0c78443254736a942e (patch) | |
tree | d1911f00911c9fc5d22f90fb8492ee87ff9506e4 | |
parent | 01358e562a8b97f50ec04025c009c71508e6d373 (diff) | |
parent | 38129a13e6e71f666e0468e99fdd932a687b4d7e (diff) | |
download | lwn-fedc1ed0f11be666de066b0c78443254736a942e.tar.gz lwn-fedc1ed0f11be666de066b0c78443254736a942e.zip |
Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs fixes from Al Viro:
"Switch mnt_hash to hlist, turning the races between __lookup_mnt() and
hash modifications into false negatives from __lookup_mnt() (instead
of hangs)"
On the false negatives from __lookup_mnt():
"The *only* thing we care about is not getting stuck in __lookup_mnt().
If it misses an entry because something in front of it just got moved
around, etc, we are fine. We'll notice that mount_lock mismatch and
that'll be it"
* 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
switch mnt_hash to hlist
don't bother with propagate_mnt() unless the target is shared
keep shadowed vfsmounts together
resizable namespace.c hashes
-rw-r--r-- | fs/mount.h | 4 | ||||
-rw-r--r-- | fs/namespace.c | 177 | ||||
-rw-r--r-- | fs/pnode.c | 26 | ||||
-rw-r--r-- | fs/pnode.h | 4 |
4 files changed, 134 insertions, 77 deletions
diff --git a/fs/mount.h b/fs/mount.h index a17458ca6f29..b29e42f05f34 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -19,13 +19,13 @@ struct mnt_pcp { }; struct mountpoint { - struct list_head m_hash; + struct hlist_node m_hash; struct dentry *m_dentry; int m_count; }; struct mount { - struct list_head mnt_hash; + struct hlist_node mnt_hash; struct mount *mnt_parent; struct dentry *mnt_mountpoint; struct vfsmount mnt; diff --git a/fs/namespace.c b/fs/namespace.c index 22e536705c45..2ffc5a2905d4 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -23,11 +23,34 @@ #include <linux/uaccess.h> #include <linux/proc_ns.h> #include <linux/magic.h> +#include <linux/bootmem.h> #include "pnode.h" #include "internal.h" -#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) -#define HASH_SIZE (1UL << HASH_SHIFT) +static unsigned int m_hash_mask __read_mostly; +static unsigned int m_hash_shift __read_mostly; +static unsigned int mp_hash_mask __read_mostly; +static unsigned int mp_hash_shift __read_mostly; + +static __initdata unsigned long mhash_entries; +static int __init set_mhash_entries(char *str) +{ + if (!str) + return 0; + mhash_entries = simple_strtoul(str, &str, 0); + return 1; +} +__setup("mhash_entries=", set_mhash_entries); + +static __initdata unsigned long mphash_entries; +static int __init set_mphash_entries(char *str) +{ + if (!str) + return 0; + mphash_entries = simple_strtoul(str, &str, 0); + return 1; +} +__setup("mphash_entries=", set_mphash_entries); static int event; static DEFINE_IDA(mnt_id_ida); @@ -36,8 +59,8 @@ static DEFINE_SPINLOCK(mnt_id_lock); static int mnt_id_start = 0; static int mnt_group_start = 1; -static struct list_head *mount_hashtable __read_mostly; -static struct list_head *mountpoint_hashtable __read_mostly; +static struct hlist_head *mount_hashtable __read_mostly; +static struct hlist_head *mountpoint_hashtable __read_mostly; static struct kmem_cache *mnt_cache __read_mostly; static DECLARE_RWSEM(namespace_sem); @@ -55,12 +78,19 @@ EXPORT_SYMBOL_GPL(fs_kobj); */ __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); -static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) +static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES); - tmp = tmp + (tmp >> HASH_SHIFT); - return tmp & (HASH_SIZE - 1); + tmp = tmp + (tmp >> m_hash_shift); + return &mount_hashtable[tmp & m_hash_mask]; +} + +static inline struct hlist_head *mp_hash(struct dentry *dentry) +{ + unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); + tmp = tmp + (tmp >> mp_hash_shift); + return &mountpoint_hashtable[tmp & mp_hash_mask]; } /* @@ -187,7 +217,7 @@ static struct mount *alloc_vfsmnt(const char *name) mnt->mnt_writers = 0; #endif - INIT_LIST_HEAD(&mnt->mnt_hash); + INIT_HLIST_NODE(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); INIT_LIST_HEAD(&mnt->mnt_mounts); INIT_LIST_HEAD(&mnt->mnt_list); @@ -575,10 +605,10 @@ bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) */ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) { - struct list_head *head = mount_hashtable + hash(mnt, dentry); + struct hlist_head *head = m_hash(mnt, dentry); struct mount *p; - list_for_each_entry_rcu(p, head, mnt_hash) + hlist_for_each_entry_rcu(p, head, mnt_hash) if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) return p; return NULL; @@ -590,13 +620,17 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) */ struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry) { - struct list_head *head = mount_hashtable + hash(mnt, dentry); - struct mount *p; - - list_for_each_entry_reverse(p, head, mnt_hash) - if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) - return p; - return NULL; + struct mount *p, *res; + res = p = __lookup_mnt(mnt, dentry); + if (!p) + goto out; + hlist_for_each_entry_continue(p, mnt_hash) { + if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry) + break; + res = p; + } +out: + return res; } /* @@ -633,11 +667,11 @@ struct vfsmount *lookup_mnt(struct path *path) static struct mountpoint *new_mountpoint(struct dentry *dentry) { - struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); + struct hlist_head *chain = mp_hash(dentry); struct mountpoint *mp; int ret; - list_for_each_entry(mp, chain, m_hash) { + hlist_for_each_entry(mp, chain, m_hash) { if (mp->m_dentry == dentry) { /* might be worth a WARN_ON() */ if (d_unlinked(dentry)) @@ -659,7 +693,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) mp->m_dentry = dentry; mp->m_count = 1; - list_add(&mp->m_hash, chain); + hlist_add_head(&mp->m_hash, chain); return mp; } @@ -670,7 +704,7 @@ static void put_mountpoint(struct mountpoint *mp) spin_lock(&dentry->d_lock); dentry->d_flags &= ~DCACHE_MOUNTED; spin_unlock(&dentry->d_lock); - list_del(&mp->m_hash); + hlist_del(&mp->m_hash); kfree(mp); } } @@ -712,7 +746,7 @@ static void detach_mnt(struct mount *mnt, struct path *old_path) mnt->mnt_parent = mnt; mnt->mnt_mountpoint = mnt->mnt.mnt_root; list_del_init(&mnt->mnt_child); - list_del_init(&mnt->mnt_hash); + hlist_del_init_rcu(&mnt->mnt_hash); put_mountpoint(mnt->mnt_mp); mnt->mnt_mp = NULL; } @@ -739,15 +773,14 @@ static void attach_mnt(struct mount *mnt, struct mountpoint *mp) { mnt_set_mountpoint(parent, mp, mnt); - list_add_tail(&mnt->mnt_hash, mount_hashtable + - hash(&parent->mnt, mp->m_dentry)); + hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry)); list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); } /* * vfsmount lock must be held for write */ -static void commit_tree(struct mount *mnt) +static void commit_tree(struct mount *mnt, struct mount *shadows) { struct mount *parent = mnt->mnt_parent; struct mount *m; @@ -762,8 +795,11 @@ static void commit_tree(struct mount *mnt) list_splice(&head, n->list.prev); - list_add_tail(&mnt->mnt_hash, mount_hashtable + - hash(&parent->mnt, mnt->mnt_mountpoint)); + if (shadows) + hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash); + else + hlist_add_head_rcu(&mnt->mnt_hash, + m_hash(&parent->mnt, mnt->mnt_mountpoint)); list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); touch_mnt_namespace(n); } @@ -1153,26 +1189,28 @@ int may_umount(struct vfsmount *mnt) EXPORT_SYMBOL(may_umount); -static LIST_HEAD(unmounted); /* protected by namespace_sem */ +static HLIST_HEAD(unmounted); /* protected by namespace_sem */ static void namespace_unlock(void) { struct mount *mnt; - LIST_HEAD(head); + struct hlist_head head = unmounted; - if (likely(list_empty(&unmounted))) { + if (likely(hlist_empty(&head))) { up_write(&namespace_sem); return; } - list_splice_init(&unmounted, &head); + head.first->pprev = &head.first; + INIT_HLIST_HEAD(&unmounted); + up_write(&namespace_sem); synchronize_rcu(); - while (!list_empty(&head)) { - mnt = list_first_entry(&head, struct mount, mnt_hash); - list_del_init(&mnt->mnt_hash); + while (!hlist_empty(&head)) { + mnt = hlist_entry(head.first, struct mount, mnt_hash); + hlist_del_init(&mnt->mnt_hash); if (mnt->mnt_ex_mountpoint.mnt) path_put(&mnt->mnt_ex_mountpoint); mntput(&mnt->mnt); @@ -1193,16 +1231,19 @@ static inline void namespace_lock(void) */ void umount_tree(struct mount *mnt, int how) { - LIST_HEAD(tmp_list); + HLIST_HEAD(tmp_list); struct mount *p; + struct mount *last = NULL; - for (p = mnt; p; p = next_mnt(p, mnt)) - list_move(&p->mnt_hash, &tmp_list); + for (p = mnt; p; p = next_mnt(p, mnt)) { + hlist_del_init_rcu(&p->mnt_hash); + hlist_add_head(&p->mnt_hash, &tmp_list); + } if (how) propagate_umount(&tmp_list); - list_for_each_entry(p, &tmp_list, mnt_hash) { + hlist_for_each_entry(p, &tmp_list, mnt_hash) { list_del_init(&p->mnt_expire); list_del_init(&p->mnt_list); __touch_mnt_namespace(p->mnt_ns); @@ -1220,8 +1261,13 @@ void umount_tree(struct mount *mnt, int how) p->mnt_mp = NULL; } change_mnt_propagation(p, MS_PRIVATE); + last = p; + } + if (last) { + last->mnt_hash.next = unmounted.first; + unmounted.first = tmp_list.first; + unmounted.first->pprev = &unmounted.first; } - list_splice(&tmp_list, &unmounted); } static void shrink_submounts(struct mount *mnt); @@ -1605,24 +1651,23 @@ static int attach_recursive_mnt(struct mount *source_mnt, struct mountpoint *dest_mp, struct path *parent_path) { - LIST_HEAD(tree_list); + HLIST_HEAD(tree_list); struct mount *child, *p; + struct hlist_node *n; int err; if (IS_MNT_SHARED(dest_mnt)) { err = invent_group_ids(source_mnt, true); if (err) goto out; - } - err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); - if (err) - goto out_cleanup_ids; - - lock_mount_hash(); - - if (IS_MNT_SHARED(dest_mnt)) { + err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); + if (err) + goto out_cleanup_ids; + lock_mount_hash(); for (p = source_mnt; p; p = next_mnt(p, source_mnt)) set_mnt_shared(p); + } else { + lock_mount_hash(); } if (parent_path) { detach_mnt(source_mnt, parent_path); @@ -1630,20 +1675,22 @@ static int attach_recursive_mnt(struct mount *source_mnt, touch_mnt_namespace(source_mnt->mnt_ns); } else { mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); - commit_tree(source_mnt); + commit_tree(source_mnt, NULL); } - list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { - list_del_init(&child->mnt_hash); - commit_tree(child); + hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { + struct mount *q; + hlist_del_init(&child->mnt_hash); + q = __lookup_mnt_last(&child->mnt_parent->mnt, + child->mnt_mountpoint); + commit_tree(child, q); } unlock_mount_hash(); return 0; out_cleanup_ids: - if (IS_MNT_SHARED(dest_mnt)) - cleanup_group_ids(source_mnt, NULL); + cleanup_group_ids(source_mnt, NULL); out: return err; } @@ -2777,18 +2824,24 @@ void __init mnt_init(void) mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); - mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); - mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); + mount_hashtable = alloc_large_system_hash("Mount-cache", + sizeof(struct hlist_head), + mhash_entries, 19, + 0, + &m_hash_shift, &m_hash_mask, 0, 0); + mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", + sizeof(struct hlist_head), + mphash_entries, 19, + 0, + &mp_hash_shift, &mp_hash_mask, 0, 0); if (!mount_hashtable || !mountpoint_hashtable) panic("Failed to allocate mount hash table\n"); - printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); - - for (u = 0; u < HASH_SIZE; u++) - INIT_LIST_HEAD(&mount_hashtable[u]); - for (u = 0; u < HASH_SIZE; u++) - INIT_LIST_HEAD(&mountpoint_hashtable[u]); + for (u = 0; u <= m_hash_mask; u++) + INIT_HLIST_HEAD(&mount_hashtable[u]); + for (u = 0; u <= mp_hash_mask; u++) + INIT_HLIST_HEAD(&mountpoint_hashtable[u]); kernfs_init(); diff --git a/fs/pnode.c b/fs/pnode.c index c7221bb19801..88396df725b4 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -220,14 +220,14 @@ static struct mount *get_source(struct mount *dest, * @tree_list : list of heads of trees to be attached. */ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp, - struct mount *source_mnt, struct list_head *tree_list) + struct mount *source_mnt, struct hlist_head *tree_list) { struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; struct mount *m, *child; int ret = 0; struct mount *prev_dest_mnt = dest_mnt; struct mount *prev_src_mnt = source_mnt; - LIST_HEAD(tmp_list); + HLIST_HEAD(tmp_list); for (m = propagation_next(dest_mnt, dest_mnt); m; m = propagation_next(m, dest_mnt)) { @@ -246,27 +246,29 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp, child = copy_tree(source, source->mnt.mnt_root, type); if (IS_ERR(child)) { ret = PTR_ERR(child); - list_splice(tree_list, tmp_list.prev); + tmp_list = *tree_list; + tmp_list.first->pprev = &tmp_list.first; + INIT_HLIST_HEAD(tree_list); goto out; } if (is_subdir(dest_mp->m_dentry, m->mnt.mnt_root)) { mnt_set_mountpoint(m, dest_mp, child); - list_add_tail(&child->mnt_hash, tree_list); + hlist_add_head(&child->mnt_hash, tree_list); } else { /* * This can happen if the parent mount was bind mounted * on some subdirectory of a shared/slave mount. */ - list_add_tail(&child->mnt_hash, &tmp_list); + hlist_add_head(&child->mnt_hash, &tmp_list); } prev_dest_mnt = m; prev_src_mnt = child; } out: lock_mount_hash(); - while (!list_empty(&tmp_list)) { - child = list_first_entry(&tmp_list, struct mount, mnt_hash); + while (!hlist_empty(&tmp_list)) { + child = hlist_entry(tmp_list.first, struct mount, mnt_hash); umount_tree(child, 0); } unlock_mount_hash(); @@ -338,8 +340,10 @@ static void __propagate_umount(struct mount *mnt) * umount the child only if the child has no * other children */ - if (child && list_empty(&child->mnt_mounts)) - list_move_tail(&child->mnt_hash, &mnt->mnt_hash); + if (child && list_empty(&child->mnt_mounts)) { + hlist_del_init_rcu(&child->mnt_hash); + hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash); + } } } @@ -350,11 +354,11 @@ static void __propagate_umount(struct mount *mnt) * * vfsmount lock must be held for write */ -int propagate_umount(struct list_head *list) +int propagate_umount(struct hlist_head *list) { struct mount *mnt; - list_for_each_entry(mnt, list, mnt_hash) + hlist_for_each_entry(mnt, list, mnt_hash) __propagate_umount(mnt); return 0; } diff --git a/fs/pnode.h b/fs/pnode.h index 59e7eda1851e..fc28a27fa892 100644 --- a/fs/pnode.h +++ b/fs/pnode.h @@ -36,8 +36,8 @@ static inline void set_mnt_shared(struct mount *mnt) void change_mnt_propagation(struct mount *, int); int propagate_mnt(struct mount *, struct mountpoint *, struct mount *, - struct list_head *); -int propagate_umount(struct list_head *); + struct hlist_head *); +int propagate_umount(struct hlist_head *); int propagate_mount_busy(struct mount *, int); void mnt_release_group_id(struct mount *); int get_dominating_id(struct mount *mnt, const struct path *root); |