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authorPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
committerPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
commit70711d223510ba1773cfe1d7770a56141c815ff8 (patch)
tree4a71f38a3a554ddecaa31b7d8c6bc49b7d1705b4 /fs/super.c
parentd53b4ed072d9779cdf53582c46436dec06d0961f (diff)
parent19f949f52599ba7c3f67a5897ac6be14bfcb1200 (diff)
Merge tag 'v3.8' of /home/kaber/src/repos/linux
Linux 3.8 Signed-off-by: Patrick McHardy <kaber@trash.net> Conflicts: include/linux/Kbuild include/linux/netlink.h
Diffstat (limited to 'fs/super.c')
-rw-r--r--fs/super.c349
1 files changed, 244 insertions, 105 deletions
diff --git a/fs/super.c b/fs/super.c
index cf001775617..12f12371216 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -33,12 +33,19 @@
#include <linux/rculist_bl.h>
#include <linux/cleancache.h>
#include <linux/fsnotify.h>
+#include <linux/lockdep.h>
#include "internal.h"
LIST_HEAD(super_blocks);
DEFINE_SPINLOCK(sb_lock);
+static char *sb_writers_name[SB_FREEZE_LEVELS] = {
+ "sb_writers",
+ "sb_pagefaults",
+ "sb_internal",
+};
+
/*
* One thing we have to be careful of with a per-sb shrinker is that we don't
* drop the last active reference to the superblock from within the shrinker.
@@ -62,7 +69,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
return -1;
if (!grab_super_passive(sb))
- return !sc->nr_to_scan ? 0 : -1;
+ return -1;
if (sb->s_op && sb->s_op->nr_cached_objects)
fs_objects = sb->s_op->nr_cached_objects(sb);
@@ -102,32 +109,63 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
return total_objects;
}
+static int init_sb_writers(struct super_block *s, struct file_system_type *type)
+{
+ int err;
+ int i;
+
+ for (i = 0; i < SB_FREEZE_LEVELS; i++) {
+ err = percpu_counter_init(&s->s_writers.counter[i], 0);
+ if (err < 0)
+ goto err_out;
+ lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i],
+ &type->s_writers_key[i], 0);
+ }
+ init_waitqueue_head(&s->s_writers.wait);
+ init_waitqueue_head(&s->s_writers.wait_unfrozen);
+ return 0;
+err_out:
+ while (--i >= 0)
+ percpu_counter_destroy(&s->s_writers.counter[i]);
+ return err;
+}
+
+static void destroy_sb_writers(struct super_block *s)
+{
+ int i;
+
+ for (i = 0; i < SB_FREEZE_LEVELS; i++)
+ percpu_counter_destroy(&s->s_writers.counter[i]);
+}
+
/**
* alloc_super - create new superblock
* @type: filesystem type superblock should belong to
+ * @flags: the mount flags
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
-static struct super_block *alloc_super(struct file_system_type *type)
+static struct super_block *alloc_super(struct file_system_type *type, int flags)
{
struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
static const struct super_operations default_op;
if (s) {
if (security_sb_alloc(s)) {
+ /*
+ * We cannot call security_sb_free() without
+ * security_sb_alloc() succeeding. So bail out manually
+ */
kfree(s);
s = NULL;
goto out;
}
#ifdef CONFIG_SMP
s->s_files = alloc_percpu(struct list_head);
- if (!s->s_files) {
- security_sb_free(s);
- kfree(s);
- s = NULL;
- goto out;
- } else {
+ if (!s->s_files)
+ goto err_out;
+ else {
int i;
for_each_possible_cpu(i)
@@ -136,6 +174,9 @@ static struct super_block *alloc_super(struct file_system_type *type)
#else
INIT_LIST_HEAD(&s->s_files);
#endif
+ if (init_sb_writers(s, type))
+ goto err_out;
+ s->s_flags = flags;
s->s_bdi = &default_backing_dev_info;
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);
@@ -145,15 +186,8 @@ static struct super_block *alloc_super(struct file_system_type *type)
spin_lock_init(&s->s_inode_lru_lock);
INIT_LIST_HEAD(&s->s_mounts);
init_rwsem(&s->s_umount);
- mutex_init(&s->s_lock);
lockdep_set_class(&s->s_umount, &type->s_umount_key);
/*
- * The locking rules for s_lock are up to the
- * filesystem. For example ext3fs has different
- * lock ordering than usbfs:
- */
- lockdep_set_class(&s->s_lock, &type->s_lock_key);
- /*
* sget() can have s_umount recursion.
*
* When it cannot find a suitable sb, it allocates a new
@@ -176,7 +210,6 @@ static struct super_block *alloc_super(struct file_system_type *type)
mutex_init(&s->s_dquot.dqio_mutex);
mutex_init(&s->s_dquot.dqonoff_mutex);
init_rwsem(&s->s_dquot.dqptr_sem);
- init_waitqueue_head(&s->s_wait_unfrozen);
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
@@ -188,6 +221,16 @@ static struct super_block *alloc_super(struct file_system_type *type)
}
out:
return s;
+err_out:
+ security_sb_free(s);
+#ifdef CONFIG_SMP
+ if (s->s_files)
+ free_percpu(s->s_files);
+#endif
+ destroy_sb_writers(s);
+ kfree(s);
+ s = NULL;
+ goto out;
}
/**
@@ -201,6 +244,7 @@ static inline void destroy_super(struct super_block *s)
#ifdef CONFIG_SMP
free_percpu(s->s_files);
#endif
+ destroy_sb_writers(s);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
kfree(s->s_subtype);
@@ -256,12 +300,6 @@ void deactivate_locked_super(struct super_block *s)
/* caches are now gone, we can safely kill the shrinker now */
unregister_shrinker(&s->s_shrink);
-
- /*
- * We need to call rcu_barrier so all the delayed rcu free
- * inodes are flushed before we release the fs module.
- */
- rcu_barrier();
put_filesystem(fs);
put_super(s);
} else {
@@ -318,7 +356,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
/*
* grab_super_passive - acquire a passive reference
- * @s: reference we are trying to grab
+ * @sb: reference we are trying to grab
*
* Tries to acquire a passive reference. This is used in places where we
* cannot take an active reference but we need to ensure that the
@@ -349,22 +387,6 @@ bool grab_super_passive(struct super_block *sb)
return false;
}
-/*
- * Superblock locking. We really ought to get rid of these two.
- */
-void lock_super(struct super_block * sb)
-{
- mutex_lock(&sb->s_lock);
-}
-
-void unlock_super(struct super_block * sb)
-{
- mutex_unlock(&sb->s_lock);
-}
-
-EXPORT_SYMBOL(lock_super);
-EXPORT_SYMBOL(unlock_super);
-
/**
* generic_shutdown_super - common helper for ->kill_sb()
* @sb: superblock to kill
@@ -415,11 +437,13 @@ EXPORT_SYMBOL(generic_shutdown_super);
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
+ * @flags: mount flags
* @data: argument to each of them
*/
struct super_block *sget(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
+ int flags,
void *data)
{
struct super_block *s = NULL;
@@ -450,7 +474,7 @@ retry:
}
if (!s) {
spin_unlock(&sb_lock);
- s = alloc_super(type);
+ s = alloc_super(type, flags);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
@@ -484,46 +508,6 @@ void drop_super(struct super_block *sb)
EXPORT_SYMBOL(drop_super);
/**
- * sync_supers - helper for periodic superblock writeback
- *
- * Call the write_super method if present on all dirty superblocks in
- * the system. This is for the periodic writeback used by most older
- * filesystems. For data integrity superblock writeback use
- * sync_filesystems() instead.
- *
- * Note: check the dirty flag before waiting, so we don't
- * hold up the sync while mounting a device. (The newly
- * mounted device won't need syncing.)
- */
-void sync_supers(void)
-{
- struct super_block *sb, *p = NULL;
-
- spin_lock(&sb_lock);
- list_for_each_entry(sb, &super_blocks, s_list) {
- if (hlist_unhashed(&sb->s_instances))
- continue;
- if (sb->s_op->write_super && sb->s_dirt) {
- sb->s_count++;
- spin_unlock(&sb_lock);
-
- down_read(&sb->s_umount);
- if (sb->s_root && sb->s_dirt && (sb->s_flags & MS_BORN))
- sb->s_op->write_super(sb);
- up_read(&sb->s_umount);
-
- spin_lock(&sb_lock);
- if (p)
- __put_super(p);
- p = sb;
- }
- }
- if (p)
- __put_super(p);
- spin_unlock(&sb_lock);
-}
-
-/**
* iterate_supers - call function for all active superblocks
* @f: function to call
* @arg: argument to pass to it
@@ -647,10 +631,11 @@ struct super_block *get_super_thawed(struct block_device *bdev)
{
while (1) {
struct super_block *s = get_super(bdev);
- if (!s || s->s_frozen == SB_UNFROZEN)
+ if (!s || s->s_writers.frozen == SB_UNFROZEN)
return s;
up_read(&s->s_umount);
- vfs_check_frozen(s, SB_FREEZE_WRITE);
+ wait_event(s->s_writers.wait_unfrozen,
+ s->s_writers.frozen == SB_UNFROZEN);
put_super(s);
}
}
@@ -728,7 +713,7 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
int retval;
int remount_ro;
- if (sb->s_frozen != SB_UNFROZEN)
+ if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
#ifdef CONFIG_BLOCK
@@ -857,7 +842,7 @@ int get_anon_bdev(dev_t *p)
else if (error)
return -EAGAIN;
- if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
+ if ((dev & MAX_IDR_MASK) == (1 << MINORBITS)) {
spin_lock(&unnamed_dev_lock);
ida_remove(&unnamed_dev_ida, dev);
if (unnamed_dev_start > dev)
@@ -925,13 +910,12 @@ struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
{
struct super_block *sb;
- sb = sget(fs_type, ns_test_super, ns_set_super, data);
+ sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
if (IS_ERR(sb))
return ERR_CAST(sb);
if (!sb->s_root) {
int err;
- sb->s_flags = flags;
err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
if (err) {
deactivate_locked_super(sb);
@@ -992,7 +976,8 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
error = -EBUSY;
goto error_bdev;
}
- s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
+ s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
+ bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
if (IS_ERR(s))
goto error_s;
@@ -1017,7 +1002,6 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
} else {
char b[BDEVNAME_SIZE];
- s->s_flags = flags | MS_NOSEC;
s->s_mode = mode;
strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
sb_set_blocksize(s, block_size(bdev));
@@ -1062,13 +1046,11 @@ struct dentry *mount_nodev(struct file_system_type *fs_type,
int (*fill_super)(struct super_block *, void *, int))
{
int error;
- struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
+ struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
- s->s_flags = flags;
-
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
@@ -1091,11 +1073,10 @@ struct dentry *mount_single(struct file_system_type *fs_type,
struct super_block *s;
int error;
- s = sget(fs_type, compare_single, set_anon_super, NULL);
+ s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
if (!s->s_root) {
- s->s_flags = flags;
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
@@ -1163,6 +1144,120 @@ out:
return ERR_PTR(error);
}
+/*
+ * This is an internal function, please use sb_end_{write,pagefault,intwrite}
+ * instead.
+ */
+void __sb_end_write(struct super_block *sb, int level)
+{
+ percpu_counter_dec(&sb->s_writers.counter[level-1]);
+ /*
+ * Make sure s_writers are updated before we wake up waiters in
+ * freeze_super().
+ */
+ smp_mb();
+ if (waitqueue_active(&sb->s_writers.wait))
+ wake_up(&sb->s_writers.wait);
+ rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_);
+}
+EXPORT_SYMBOL(__sb_end_write);
+
+#ifdef CONFIG_LOCKDEP
+/*
+ * We want lockdep to tell us about possible deadlocks with freezing but
+ * it's it bit tricky to properly instrument it. Getting a freeze protection
+ * works as getting a read lock but there are subtle problems. XFS for example
+ * gets freeze protection on internal level twice in some cases, which is OK
+ * only because we already hold a freeze protection also on higher level. Due
+ * to these cases we have to tell lockdep we are doing trylock when we
+ * already hold a freeze protection for a higher freeze level.
+ */
+static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock,
+ unsigned long ip)
+{
+ int i;
+
+ if (!trylock) {
+ for (i = 0; i < level - 1; i++)
+ if (lock_is_held(&sb->s_writers.lock_map[i])) {
+ trylock = true;
+ break;
+ }
+ }
+ rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip);
+}
+#endif
+
+/*
+ * This is an internal function, please use sb_start_{write,pagefault,intwrite}
+ * instead.
+ */
+int __sb_start_write(struct super_block *sb, int level, bool wait)
+{
+retry:
+ if (unlikely(sb->s_writers.frozen >= level)) {
+ if (!wait)
+ return 0;
+ wait_event(sb->s_writers.wait_unfrozen,
+ sb->s_writers.frozen < level);
+ }
+
+#ifdef CONFIG_LOCKDEP
+ acquire_freeze_lock(sb, level, !wait, _RET_IP_);
+#endif
+ percpu_counter_inc(&sb->s_writers.counter[level-1]);
+ /*
+ * Make sure counter is updated before we check for frozen.
+ * freeze_super() first sets frozen and then checks the counter.
+ */
+ smp_mb();
+ if (unlikely(sb->s_writers.frozen >= level)) {
+ __sb_end_write(sb, level);
+ goto retry;
+ }
+ return 1;
+}
+EXPORT_SYMBOL(__sb_start_write);
+
+/**
+ * sb_wait_write - wait until all writers to given file system finish
+ * @sb: the super for which we wait
+ * @level: type of writers we wait for (normal vs page fault)
+ *
+ * This function waits until there are no writers of given type to given file
+ * system. Caller of this function should make sure there can be no new writers
+ * of type @level before calling this function. Otherwise this function can
+ * livelock.
+ */
+static void sb_wait_write(struct super_block *sb, int level)
+{
+ s64 writers;
+
+ /*
+ * We just cycle-through lockdep here so that it does not complain
+ * about returning with lock to userspace
+ */
+ rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
+ rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
+
+ do {
+ DEFINE_WAIT(wait);
+
+ /*
+ * We use a barrier in prepare_to_wait() to separate setting
+ * of frozen and checking of the counter
+ */
+ prepare_to_wait(&sb->s_writers.wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ writers = percpu_counter_sum(&sb->s_writers.counter[level-1]);
+ if (writers)
+ schedule();
+
+ finish_wait(&sb->s_writers.wait, &wait);
+ } while (writers);
+}
+
/**
* freeze_super - lock the filesystem and force it into a consistent state
* @sb: the super to lock
@@ -1170,6 +1265,31 @@ out:
* Syncs the super to make sure the filesystem is consistent and calls the fs's
* freeze_fs. Subsequent calls to this without first thawing the fs will return
* -EBUSY.
+ *
+ * During this function, sb->s_writers.frozen goes through these values:
+ *
+ * SB_UNFROZEN: File system is normal, all writes progress as usual.
+ *
+ * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
+ * writes should be blocked, though page faults are still allowed. We wait for
+ * all writes to complete and then proceed to the next stage.
+ *
+ * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
+ * but internal fs threads can still modify the filesystem (although they
+ * should not dirty new pages or inodes), writeback can run etc. After waiting
+ * for all running page faults we sync the filesystem which will clean all
+ * dirty pages and inodes (no new dirty pages or inodes can be created when
+ * sync is running).
+ *
+ * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
+ * modification are blocked (e.g. XFS preallocation truncation on inode
+ * reclaim). This is usually implemented by blocking new transactions for
+ * filesystems that have them and need this additional guard. After all
+ * internal writers are finished we call ->freeze_fs() to finish filesystem
+ * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
+ * mostly auxiliary for filesystems to verify they do not modify frozen fs.
+ *
+ * sb->s_writers.frozen is protected by sb->s_umount.
*/
int freeze_super(struct super_block *sb)
{
@@ -1177,7 +1297,7 @@ int freeze_super(struct super_block *sb)
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
- if (sb->s_frozen) {
+ if (sb->s_writers.frozen != SB_UNFROZEN) {
deactivate_locked_super(sb);
return -EBUSY;
}
@@ -1188,33 +1308,53 @@ int freeze_super(struct super_block *sb)
}
if (sb->s_flags & MS_RDONLY) {
- sb->s_frozen = SB_FREEZE_TRANS;
- smp_wmb();
+ /* Nothing to do really... */
+ sb->s_writers.frozen = SB_FREEZE_COMPLETE;
up_write(&sb->s_umount);
return 0;
}
- sb->s_frozen = SB_FREEZE_WRITE;
+ /* From now on, no new normal writers can start */
+ sb->s_writers.frozen = SB_FREEZE_WRITE;
smp_wmb();
+ /* Release s_umount to preserve sb_start_write -> s_umount ordering */
+ up_write(&sb->s_umount);
+
+ sb_wait_write(sb, SB_FREEZE_WRITE);
+
+ /* Now we go and block page faults... */
+ down_write(&sb->s_umount);
+ sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
+ smp_wmb();
+
+ sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
+
+ /* All writers are done so after syncing there won't be dirty data */
sync_filesystem(sb);
- sb->s_frozen = SB_FREEZE_TRANS;
+ /* Now wait for internal filesystem counter */
+ sb->s_writers.frozen = SB_FREEZE_FS;
smp_wmb();
+ sb_wait_write(sb, SB_FREEZE_FS);
- sync_blockdev(sb->s_bdev);
if (sb->s_op->freeze_fs) {
ret = sb->s_op->freeze_fs(sb);
if (ret) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
- sb->s_frozen = SB_UNFROZEN;
+ sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
- wake_up(&sb->s_wait_unfrozen);
+ wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return ret;
}
}
+ /*
+ * This is just for debugging purposes so that fs can warn if it
+ * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
+ */
+ sb->s_writers.frozen = SB_FREEZE_COMPLETE;
up_write(&sb->s_umount);
return 0;
}
@@ -1231,7 +1371,7 @@ int thaw_super(struct super_block *sb)
int error;
down_write(&sb->s_umount);
- if (sb->s_frozen == SB_UNFROZEN) {
+ if (sb->s_writers.frozen == SB_UNFROZEN) {
up_write(&sb->s_umount);
return -EINVAL;
}
@@ -1244,16 +1384,15 @@ int thaw_super(struct super_block *sb)
if (error) {
printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
- sb->s_frozen = SB_FREEZE_TRANS;
up_write(&sb->s_umount);
return error;
}
}
out:
- sb->s_frozen = SB_UNFROZEN;
+ sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
- wake_up(&sb->s_wait_unfrozen);
+ wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return 0;