[PATCH v4 0/8] Fix freeze/sysfs deadlock in better method.

[PATCH v4 0/8] Fix freeze/sysfs deadlock in better method.

[Qu Wenruo]

Patchset to solve the previous found freeze/sysfs deadlock.

Unlike previous pending_changes, which uses transaction commits to
ensure mount option doesn't change during transaction.
This idea is great in concept, but will introduce extra and somewhat
duplicated ro/freeze check, and the original synchronized behavior is
also changed.

[Per-transaction mount option]
This patch use the RCU-like concept, which will copy the mount_opt from
fs_info into btrfs_transaction, and each btrfs_test_opt() for specific
mount option bit(SPACE_CACHE/INODE_MAP_CACHE) should be changed to
btrfs_test_trans_opt().
So mount option during transaction won't be changed, and also, no extra
read_only or freeze check is needed, the commit routine is also
untouched.

[Use VFS protect for sysfs change]
The 6th patch will introduce a new help function get_vfsmount_sb() to
get a vfsmount from a sb, with this vfsmount, we can use vfs level
mnt_want_write() to do a comprehensive protection other than the cheap
ro/freeze check.

Qu Wenruo (8):
  Revert "btrfs: add support for processing pending changes" related    
    commits
  btrfs: Make btrfs_parse_options() parse mount option in a atomic way
  btrfs: Introduce per-transaction mount_opt to keep mount option    
    consistent during transaction.
  btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under 
       transaction protect.
  btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE if it's under 
       transaction protect.
  vfs: Add get_vfsmount_sb() function to get vfsmount from a given sb.
  btrfs: Use mnt_want_write() to protect label change.
  btrfs: Use mnt_want_write() to protect sysfs feature change.

 fs/btrfs/ctree.h            |  64 +++-------------------
 fs/btrfs/disk-io.c          |   6 ---
 fs/btrfs/extent-tree.c      |   2 +-
 fs/btrfs/free-space-cache.c |   2 +-
 fs/btrfs/inode-map.c        |   5 +-
 fs/btrfs/super.c            | 129 ++++++++++++++++++++++----------------------
 fs/btrfs/sysfs.c            |  73 ++++++++++++++++++-------
 fs/btrfs/transaction.c      |  43 ++-------------
 fs/btrfs/transaction.h      |   6 ++-
 fs/namespace.c              |  25 +++++++++
 include/linux/mount.h       |   1 +
 11 files changed, 167 insertions(+), 189 deletions(-)

-- 
2.2.2

[PATCH v4 1/8] Revert "btrfs: add support for processing pending changes" related commits

[Qu Wenruo]

This reverts commit 572d9ab7845 ~ a6f69dc8018.

This pending commits patches introduce deadlock with freeze, and fix for
it will introduce extra checks on freeze and read only case.

For mount option change, later patches will introduce per-transaction
mount option to keep mount options consistent during transaction.

For sysfs interface to change label/features, it will use
mnt_want_write() to do the ro/freeze check and keep the 'btrfs pro set'
synchronized behavior.

Revert them to a clean base for later changes.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>

Conflicts:
	fs/btrfs/ctree.h
	fs/btrfs/super.c
---
 fs/btrfs/ctree.h       | 49 +------------------------------------------------
 fs/btrfs/disk-io.c     |  8 +++-----
 fs/btrfs/inode-map.c   |  2 +-
 fs/btrfs/super.c       | 14 +++-----------
 fs/btrfs/sysfs.c       | 34 +++++++++++++++++++++-------------
 fs/btrfs/transaction.c | 38 ++++++--------------------------------
 fs/btrfs/transaction.h |  2 --
 7 files changed, 35 insertions(+), 112 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 7e60741..5f99743 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1411,11 +1411,6 @@ struct btrfs_fs_info {
 	 */
 	u64 last_trans_log_full_commit;
 	unsigned long mount_opt;
-	/*
-	 * Track requests for actions that need to be done during transaction
-	 * commit (like for some mount options).
-	 */
-	unsigned long pending_changes;
 	unsigned long compress_type:4;
 	int commit_interval;
 	/*
@@ -2113,6 +2108,7 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
 #define BTRFS_MOUNT_RESCAN_UUID_TREE	(1 << 23)
+#define	BTRFS_MOUNT_CHANGE_INODE_CACHE	(1 << 24)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(8192)
@@ -2138,49 +2134,6 @@ struct btrfs_ioctl_defrag_range_args {
 }
 
 /*
- * Requests for changes that need to be done during transaction commit.
- *
- * Internal mount options that are used for special handling of the real
- * mount options (eg. cannot be set during remount and have to be set during
- * transaction commit)
- */
-
-#define BTRFS_PENDING_SET_INODE_MAP_CACHE	(0)
-#define BTRFS_PENDING_CLEAR_INODE_MAP_CACHE	(1)
-#define BTRFS_PENDING_COMMIT			(2)
-
-#define btrfs_test_pending(info, opt)	\
-	test_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
-#define btrfs_set_pending(info, opt)	\
-	set_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
-#define btrfs_clear_pending(info, opt)	\
-	clear_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
-
-/*
- * Helpers for setting pending mount option changes.
- *
- * Expects corresponding macros
- * BTRFS_PENDING_SET_ and CLEAR_ + short mount option name
- */
-#define btrfs_set_pending_and_info(info, opt, fmt, args...)            \
-do {                                                                   \
-       if (!btrfs_raw_test_opt((info)->mount_opt, opt)) {              \
-               btrfs_info((info), fmt, ##args);                        \
-               btrfs_set_pending((info), SET_##opt);                   \
-               btrfs_clear_pending((info), CLEAR_##opt);               \
-       }                                                               \
-} while(0)
-
-#define btrfs_clear_pending_and_info(info, opt, fmt, args...)          \
-do {                                                                   \
-       if (btrfs_raw_test_opt((info)->mount_opt, opt)) {               \
-               btrfs_info((info), fmt, ##args);                        \
-               btrfs_set_pending((info), CLEAR_##opt);                 \
-               btrfs_clear_pending((info), SET_##opt);                 \
-       }                                                               \
-} while(0)
-
-/*
  * Inode flags
  */
 #define BTRFS_INODE_NODATASUM		(1 << 0)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8c63419..2d3c8b7 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2832,11 +2832,9 @@ retry_root_backup:
 		btrfs_set_opt(fs_info->mount_opt, SSD);
 	}
 
-	/*
-	 * Mount does not set all options immediatelly, we can do it now and do
-	 * not have to wait for transaction commit
-	 */
-	btrfs_apply_pending_changes(fs_info);
+	/* Set the real inode map cache flag */
+	if (btrfs_test_opt(tree_root, CHANGE_INODE_CACHE))
+		btrfs_set_opt(tree_root->fs_info->mount_opt, INODE_MAP_CACHE);
 
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 74faea3..81efd83 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -178,7 +178,7 @@ static void start_caching(struct btrfs_root *root)
 			  root->root_key.objectid);
 	if (IS_ERR(tsk)) {
 		btrfs_warn(root->fs_info, "failed to start inode caching task");
-		btrfs_clear_pending_and_info(root->fs_info, INODE_MAP_CACHE,
+		btrfs_clear_and_info(root, CHANGE_INODE_CACHE,
 				"disabling inode map caching");
 	}
 }
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 60f7cbe..b0c45b2 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -993,17 +993,9 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 	trans = btrfs_attach_transaction_barrier(root);
 	if (IS_ERR(trans)) {
 		/* no transaction, don't bother */
-		if (PTR_ERR(trans) == -ENOENT) {
-			/*
-			 * Exit unless we have some pending changes
-			 * that need to go through commit
-			 */
-			if (fs_info->pending_changes == 0)
-				return 0;
-			trans = btrfs_start_transaction(root, 0);
-		} else {
-			return PTR_ERR(trans);
-		}
+		if (PTR_ERR(trans) == -ENOENT)
+			return 0;
+		return PTR_ERR(trans);
 	}
 	return btrfs_commit_transaction(trans, root);
 }
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 92db3f6..b2e7bb4 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -111,6 +111,7 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_feature_attr *fa = to_btrfs_feature_attr(a);
+	struct btrfs_trans_handle *trans;
 	u64 features, set, clear;
 	unsigned long val;
 	int ret;
@@ -152,6 +153,10 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 	btrfs_info(fs_info, "%s %s feature flag",
 		   val ? "Setting" : "Clearing", fa->kobj_attr.attr.name);
 
+	trans = btrfs_start_transaction(fs_info->fs_root, 0);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
 	spin_lock(&fs_info->super_lock);
 	features = get_features(fs_info, fa->feature_set);
 	if (val)
@@ -161,11 +166,9 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 	set_features(fs_info, fa->feature_set, features);
 	spin_unlock(&fs_info->super_lock);
 
-	/*
-	 * We don't want to do full transaction commit from inside sysfs
-	 */
-	btrfs_set_pending(fs_info, COMMIT);
-	wake_up_process(fs_info->transaction_kthread);
+	ret = btrfs_commit_transaction(trans, fs_info->fs_root);
+	if (ret)
+		return ret;
 
 	return count;
 }
@@ -369,6 +372,9 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 				 const char *buf, size_t len)
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root = fs_info->fs_root;
+	int ret;
 	size_t p_len;
 
 	if (fs_info->sb->s_flags & MS_RDONLY)
@@ -383,18 +389,20 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 	if (p_len >= BTRFS_LABEL_SIZE)
 		return -EINVAL;
 
-	spin_lock(&fs_info->super_lock);
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	spin_lock(&root->fs_info->super_lock);
 	memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
 	memcpy(fs_info->super_copy->label, buf, p_len);
-	spin_unlock(&fs_info->super_lock);
+	spin_unlock(&root->fs_info->super_lock);
+	ret = btrfs_commit_transaction(trans, root);
 
-	/*
-	 * We don't want to do full transaction commit from inside sysfs
-	 */
-	btrfs_set_pending(fs_info, COMMIT);
-	wake_up_process(fs_info->transaction_kthread);
+	if (!ret)
+		return len;
 
-	return len;
+	return ret;
 }
 BTRFS_ATTR_RW(label, btrfs_label_show, btrfs_label_store);
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a605d4e..295a135 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1938,10 +1938,13 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	}
 
 	/*
-	 * Since the transaction is done, we can apply the pending changes
-	 * before the next transaction.
+	 * Since the transaction is done, we should set the inode map cache flag
+	 * before any other comming transaction.
 	 */
-	btrfs_apply_pending_changes(root->fs_info);
+	if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
+		btrfs_set_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
+	else
+		btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
 
 	/* commit_fs_roots gets rid of all the tree log roots, it is now
 	 * safe to free the root of tree log roots
@@ -2112,32 +2115,3 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
 
 	return (ret < 0) ? 0 : 1;
 }
-
-void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
-{
-	unsigned long prev;
-	unsigned long bit;
-
-	prev = cmpxchg(&fs_info->pending_changes, 0, 0);
-	if (!prev)
-		return;
-
-	bit = 1 << BTRFS_PENDING_SET_INODE_MAP_CACHE;
-	if (prev & bit)
-		btrfs_set_opt(fs_info->mount_opt, INODE_MAP_CACHE);
-	prev &= ~bit;
-
-	bit = 1 << BTRFS_PENDING_CLEAR_INODE_MAP_CACHE;
-	if (prev & bit)
-		btrfs_clear_opt(fs_info->mount_opt, INODE_MAP_CACHE);
-	prev &= ~bit;
-
-	bit = 1 << BTRFS_PENDING_COMMIT;
-	if (prev & bit)
-		btrfs_debug(fs_info, "pending commit done");
-	prev &= ~bit;
-
-	if (prev)
-		btrfs_warn(fs_info,
-			"unknown pending changes left 0x%lx, ignoring", prev);
-}
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 00ed29c..fd400a3 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -170,6 +170,4 @@ int btrfs_wait_marked_extents(struct btrfs_root *root,
 int btrfs_transaction_blocked(struct btrfs_fs_info *info);
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
 void btrfs_put_transaction(struct btrfs_transaction *transaction);
-void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info);
-
 #endif
-- 
2.2.2

[PATCH v4 2/8] btrfs: Introduce per-transaction mount_opt to keep mount option consistent during transaction.

[Qu Wenruo]

Before this patch, mount_opt is not consistent during a transaction.
btrfs_parse_options() can race with transaction.

Now each transaction will keep a copy of fs_info->mount_opt upon
creation, and new btrfs_test_trans_opt() macro is introduced to get the
mount_opt in the transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/transaction.c | 1 +
 fs/btrfs/transaction.h | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 295a135..846e1b8 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -210,6 +210,7 @@ loop:
 		return -EROFS;
 	}
 
+	cur_trans->mount_opt = fs_info->mount_opt;
 	atomic_set(&cur_trans->num_writers, 1);
 	extwriter_counter_init(cur_trans, type);
 	init_waitqueue_head(&cur_trans->writer_wait);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index fd400a3..4052879 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -52,6 +52,7 @@ struct btrfs_transaction {
 	struct list_head list;
 	struct extent_io_tree dirty_pages;
 	unsigned long start_time;
+	unsigned long mount_opt;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
 	struct list_head pending_snapshots;
@@ -126,6 +127,9 @@ struct btrfs_pending_snapshot {
 	struct list_head list;
 };
 
+#define btrfs_test_trans_opt(trans, opt)	\
+	(btrfs_raw_test_opt(trans->transaction->mount_opt, opt))
+
 static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
 					      struct inode *inode)
 {
-- 
2.2.2

[PATCH v4 2/8] btrfs: Make btrfs_parse_options() parse mount option in a atomic way

[Qu Wenruo]

Current btrfs_parse_options() is not atomic, which can set and clear a
bit, especially for nospace_cache case.

For example, if a fs is mounted with nospace_cache,
btrfs_parse_options() will set SPACE_CACHE bit first(since
cache_generation is non-zeo) and clear the SPACE_CACHE bit due to
nospace_cache mount option.
So under heavy operations and remount a nospace_cache btrfs, there is a
windows for commit to create space cache.

This bug can be reproduced by fstest/btrfs/071 073 074 with
nospace_cache mount option. It has about 50% chance to create space
cache, and about 10% chance to create wrong space cache, which can't
pass btrfsck.

This patch will do the mount option parse in a copy-and-update method.
First copy the mount_opt from fs_info to new_opt, and only update
options in new_opt. At last, copy the new_opt back to
fs_info->mount_opt.

This patch is already good enough to fix the above nospace_cache +
remount bug, but need later patch to make sure mount options does not
change during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/ctree.h |  16 ++++----
 fs/btrfs/super.c | 115 +++++++++++++++++++++++++++++--------------------------
 2 files changed, 69 insertions(+), 62 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5f99743..26bb47b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2119,18 +2119,18 @@ struct btrfs_ioctl_defrag_range_args {
 #define btrfs_test_opt(root, opt)	((root)->fs_info->mount_opt & \
 					 BTRFS_MOUNT_##opt)
 
-#define btrfs_set_and_info(root, opt, fmt, args...)			\
+#define btrfs_set_and_info(fs_info, val, opt, fmt, args...)		\
 {									\
-	if (!btrfs_test_opt(root, opt))					\
-		btrfs_info(root->fs_info, fmt, ##args);			\
-	btrfs_set_opt(root->fs_info->mount_opt, opt);			\
+	if (!btrfs_raw_test_opt(val, opt))				\
+		btrfs_info(fs_info, fmt, ##args);			\
+	btrfs_set_opt(val, opt);					\
 }
 
-#define btrfs_clear_and_info(root, opt, fmt, args...)			\
+#define btrfs_clear_and_info(fs_info, val, opt, fmt, args...)		\
 {									\
-	if (btrfs_test_opt(root, opt))					\
-		btrfs_info(root->fs_info, fmt, ##args);			\
-	btrfs_clear_opt(root->fs_info->mount_opt, opt);			\
+	if (btrfs_raw_test_opt(val, opt))				\
+		btrfs_info(fs_info, fmt, ##args);			\
+	btrfs_clear_opt(val, opt);					\
 }
 
 /*
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b0c45b2..490fe1f 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -395,10 +395,13 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 	int ret = 0;
 	char *compress_type;
 	bool compress_force = false;
+	unsigned long new_opt;
+
+	new_opt = info->mount_opt;
 
 	cache_gen = btrfs_super_cache_generation(root->fs_info->super_copy);
 	if (cache_gen)
-		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+		btrfs_set_opt(new_opt, SPACE_CACHE);
 
 	if (!options)
 		goto out;
@@ -422,7 +425,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		switch (token) {
 		case Opt_degraded:
 			btrfs_info(root->fs_info, "allowing degraded mounts");
-			btrfs_set_opt(info->mount_opt, DEGRADED);
+			btrfs_set_opt(new_opt, DEGRADED);
 			break;
 		case Opt_subvol:
 		case Opt_subvolid:
@@ -434,7 +437,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			 */
 			break;
 		case Opt_nodatasum:
-			btrfs_set_and_info(root, NODATASUM,
+			btrfs_set_and_info(info, new_opt, NODATASUM,
 					   "setting nodatasum");
 			break;
 		case Opt_datasum:
@@ -444,8 +447,8 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				else
 					btrfs_info(root->fs_info, "setting datasum");
 			}
-			btrfs_clear_opt(info->mount_opt, NODATACOW);
-			btrfs_clear_opt(info->mount_opt, NODATASUM);
+			btrfs_clear_opt(new_opt, NODATACOW);
+			btrfs_clear_opt(new_opt, NODATASUM);
 			break;
 		case Opt_nodatacow:
 			if (!btrfs_test_opt(root, NODATACOW)) {
@@ -457,13 +460,13 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 					btrfs_info(root->fs_info, "setting nodatacow");
 				}
 			}
-			btrfs_clear_opt(info->mount_opt, COMPRESS);
-			btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
-			btrfs_set_opt(info->mount_opt, NODATACOW);
-			btrfs_set_opt(info->mount_opt, NODATASUM);
+			btrfs_clear_opt(new_opt, COMPRESS);
+			btrfs_clear_opt(new_opt, FORCE_COMPRESS);
+			btrfs_set_opt(new_opt, NODATACOW);
+			btrfs_set_opt(new_opt, NODATASUM);
 			break;
 		case Opt_datacow:
-			btrfs_clear_and_info(root, NODATACOW,
+			btrfs_clear_and_info(info, new_opt, NODATACOW,
 					     "setting datacow");
 			break;
 		case Opt_compress_force:
@@ -477,20 +480,20 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			    strcmp(args[0].from, "zlib") == 0) {
 				compress_type = "zlib";
 				info->compress_type = BTRFS_COMPRESS_ZLIB;
-				btrfs_set_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, NODATACOW);
-				btrfs_clear_opt(info->mount_opt, NODATASUM);
+				btrfs_set_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, NODATACOW);
+				btrfs_clear_opt(new_opt, NODATASUM);
 			} else if (strcmp(args[0].from, "lzo") == 0) {
 				compress_type = "lzo";
 				info->compress_type = BTRFS_COMPRESS_LZO;
-				btrfs_set_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, NODATACOW);
-				btrfs_clear_opt(info->mount_opt, NODATASUM);
+				btrfs_set_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, NODATACOW);
+				btrfs_clear_opt(new_opt, NODATASUM);
 				btrfs_set_fs_incompat(info, COMPRESS_LZO);
 			} else if (strncmp(args[0].from, "no", 2) == 0) {
 				compress_type = "no";
-				btrfs_clear_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
+				btrfs_clear_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, FORCE_COMPRESS);
 				compress_force = false;
 			} else {
 				ret = -EINVAL;
@@ -498,7 +501,8 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			}
 
 			if (compress_force) {
-				btrfs_set_and_info(root, FORCE_COMPRESS,
+				btrfs_set_and_info(info, new_opt,
+						   FORCE_COMPRESS,
 						   "force %s compression",
 						   compress_type);
 			} else {
@@ -512,29 +516,29 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				 * flag, otherwise, there is no way for users
 				 * to disable forcible compression separately.
 				 */
-				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
+				btrfs_clear_opt(new_opt, FORCE_COMPRESS);
 			}
 			break;
 		case Opt_ssd:
-			btrfs_set_and_info(root, SSD,
+			btrfs_set_and_info(info, new_opt, SSD,
 					   "use ssd allocation scheme");
 			break;
 		case Opt_ssd_spread:
-			btrfs_set_and_info(root, SSD_SPREAD,
+			btrfs_set_and_info(info, new_opt, SSD_SPREAD,
 					   "use spread ssd allocation scheme");
-			btrfs_set_opt(info->mount_opt, SSD);
+			btrfs_set_opt(new_opt, SSD);
 			break;
 		case Opt_nossd:
-			btrfs_set_and_info(root, NOSSD,
-					     "not using ssd allocation scheme");
-			btrfs_clear_opt(info->mount_opt, SSD);
+			btrfs_set_and_info(info, new_opt, NOSSD,
+					   "not using ssd allocation scheme");
+			btrfs_clear_opt(new_opt, SSD);
 			break;
 		case Opt_barrier:
-			btrfs_clear_and_info(root, NOBARRIER,
+			btrfs_clear_and_info(info, new_opt, NOBARRIER,
 					     "turning on barriers");
 			break;
 		case Opt_nobarrier:
-			btrfs_set_and_info(root, NOBARRIER,
+			btrfs_set_and_info(info, new_opt, NOBARRIER,
 					   "turning off barriers");
 			break;
 		case Opt_thread_pool:
@@ -594,19 +598,19 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 			break;
 		case Opt_notreelog:
-			btrfs_set_and_info(root, NOTREELOG,
+			btrfs_set_and_info(info, new_opt, NOTREELOG,
 					   "disabling tree log");
 			break;
 		case Opt_treelog:
-			btrfs_clear_and_info(root, NOTREELOG,
+			btrfs_clear_and_info(info, new_opt, NOTREELOG,
 					     "enabling tree log");
 			break;
 		case Opt_flushoncommit:
-			btrfs_set_and_info(root, FLUSHONCOMMIT,
+			btrfs_set_and_info(info, new_opt, FLUSHONCOMMIT,
 					   "turning on flush-on-commit");
 			break;
 		case Opt_noflushoncommit:
-			btrfs_clear_and_info(root, FLUSHONCOMMIT,
+			btrfs_clear_and_info(info, new_opt, FLUSHONCOMMIT,
 					     "turning off flush-on-commit");
 			break;
 		case Opt_ratio:
@@ -623,71 +627,71 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			}
 			break;
 		case Opt_discard:
-			btrfs_set_and_info(root, DISCARD,
+			btrfs_set_and_info(info, new_opt, DISCARD,
 					   "turning on discard");
 			break;
 		case Opt_nodiscard:
-			btrfs_clear_and_info(root, DISCARD,
+			btrfs_clear_and_info(info, new_opt, DISCARD,
 					     "turning off discard");
 			break;
 		case Opt_space_cache:
-			btrfs_set_and_info(root, SPACE_CACHE,
+			btrfs_set_and_info(info, new_opt, SPACE_CACHE,
 					   "enabling disk space caching");
 			break;
 		case Opt_rescan_uuid_tree:
-			btrfs_set_opt(info->mount_opt, RESCAN_UUID_TREE);
+			btrfs_set_opt(new_opt, RESCAN_UUID_TREE);
 			break;
 		case Opt_no_space_cache:
-			btrfs_clear_and_info(root, SPACE_CACHE,
+			btrfs_clear_and_info(info, new_opt, SPACE_CACHE,
 					     "disabling disk space caching");
 			break;
 		case Opt_inode_cache:
-			btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
+			btrfs_set_and_info(info, new_opt, INODE_MAP_CACHE,
 					   "enabling inode map caching");
 			break;
 		case Opt_noinode_cache:
-			btrfs_clear_pending_and_info(info, INODE_MAP_CACHE,
+			btrfs_clear_and_info(info, new_opt, INODE_MAP_CACHE,
 					     "disabling inode map caching");
 			break;
 		case Opt_clear_cache:
-			btrfs_set_and_info(root, CLEAR_CACHE,
+			btrfs_set_and_info(info, new_opt, CLEAR_CACHE,
 					   "force clearing of disk cache");
 			break;
 		case Opt_user_subvol_rm_allowed:
-			btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
+			btrfs_set_opt(new_opt, USER_SUBVOL_RM_ALLOWED);
 			break;
 		case Opt_enospc_debug:
-			btrfs_set_opt(info->mount_opt, ENOSPC_DEBUG);
+			btrfs_set_opt(new_opt, ENOSPC_DEBUG);
 			break;
 		case Opt_noenospc_debug:
-			btrfs_clear_opt(info->mount_opt, ENOSPC_DEBUG);
+			btrfs_clear_opt(new_opt, ENOSPC_DEBUG);
 			break;
 		case Opt_defrag:
-			btrfs_set_and_info(root, AUTO_DEFRAG,
+			btrfs_set_and_info(info, new_opt, AUTO_DEFRAG,
 					   "enabling auto defrag");
 			break;
 		case Opt_nodefrag:
-			btrfs_clear_and_info(root, AUTO_DEFRAG,
+			btrfs_clear_and_info(info, new_opt, AUTO_DEFRAG,
 					     "disabling auto defrag");
 			break;
 		case Opt_recovery:
 			btrfs_info(root->fs_info, "enabling auto recovery");
-			btrfs_set_opt(info->mount_opt, RECOVERY);
+			btrfs_set_opt(new_opt, RECOVERY);
 			break;
 		case Opt_skip_balance:
-			btrfs_set_opt(info->mount_opt, SKIP_BALANCE);
+			btrfs_set_opt(new_opt, SKIP_BALANCE);
 			break;
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 		case Opt_check_integrity_including_extent_data:
 			btrfs_info(root->fs_info,
 				   "enabling check integrity including extent data");
-			btrfs_set_opt(info->mount_opt,
+			btrfs_set_opt(new_opt,
 				      CHECK_INTEGRITY_INCLUDING_EXTENT_DATA);
-			btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
+			btrfs_set_opt(new_opt, CHECK_INTEGRITY);
 			break;
 		case Opt_check_integrity:
 			btrfs_info(root->fs_info, "enabling check integrity");
-			btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
+			btrfs_set_opt(new_opt, CHECK_INTEGRITY);
 			break;
 		case Opt_check_integrity_print_mask:
 			ret = match_int(&args[0], &intarg);
@@ -713,10 +717,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 #endif
 		case Opt_fatal_errors:
 			if (strcmp(args[0].from, "panic") == 0)
-				btrfs_set_opt(info->mount_opt,
+				btrfs_set_opt(new_opt,
 					      PANIC_ON_FATAL_ERROR);
 			else if (strcmp(args[0].from, "bug") == 0)
-				btrfs_clear_opt(info->mount_opt,
+				btrfs_clear_opt(new_opt,
 					      PANIC_ON_FATAL_ERROR);
 			else {
 				ret = -EINVAL;
@@ -752,8 +756,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		}
 	}
 out:
-	if (!ret && btrfs_test_opt(root, SPACE_CACHE))
-		btrfs_info(root->fs_info, "disk space caching is enabled");
+	if (!ret) {
+		if (btrfs_raw_test_opt(new_opt, SPACE_CACHE))
+			btrfs_info(info, "disk space caching is enabled");
+		info->mount_opt = new_opt;
+	}
 	kfree(orig);
 	return ret;
 }
-- 
2.2.2

[PATCH v4 3/8] btrfs: Introduce per-transaction mount_opt to keep mount option consistent during transaction.

[Qu Wenruo]

Before this patch, mount_opt is not consistent during a transaction.
btrfs_parse_options() can race with transaction.

Now each transaction will keep a copy of fs_info->mount_opt upon
creation, and new btrfs_test_trans_opt() macro is introduced to get the
mount_opt in the transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/transaction.c | 1 +
 fs/btrfs/transaction.h | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 295a135..846e1b8 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -210,6 +210,7 @@ loop:
 		return -EROFS;
 	}
 
+	cur_trans->mount_opt = fs_info->mount_opt;
 	atomic_set(&cur_trans->num_writers, 1);
 	extwriter_counter_init(cur_trans, type);
 	init_waitqueue_head(&cur_trans->writer_wait);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index fd400a3..4052879 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -52,6 +52,7 @@ struct btrfs_transaction {
 	struct list_head list;
 	struct extent_io_tree dirty_pages;
 	unsigned long start_time;
+	unsigned long mount_opt;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
 	struct list_head pending_snapshots;
@@ -126,6 +127,9 @@ struct btrfs_pending_snapshot {
 	struct list_head list;
 };
 
+#define btrfs_test_trans_opt(trans, opt)	\
+	(btrfs_raw_test_opt(trans->transaction->mount_opt, opt))
+
 static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
 					      struct inode *inode)
 {
-- 
2.2.2

[PATCH v4 3/8] btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under transaction protect.

[Qu Wenruo]

Convert btrfs_test_opt() to btrfs_test_trans_opt() if it's called under
transaction protection.
This will ensure SPACE_CACHE bit is consistent during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/extent-tree.c | 2 +-
 fs/btrfs/transaction.c | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1511658..c968d12 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3260,7 +3260,7 @@ again:
 
 	spin_lock(&block_group->lock);
 	if (block_group->cached != BTRFS_CACHE_FINISHED ||
-	    !btrfs_test_opt(root, SPACE_CACHE) ||
+	    !btrfs_test_trans_opt(trans, SPACE_CACHE) ||
 	    block_group->delalloc_bytes) {
 		/*
 		 * don't bother trying to write stuff out _if_
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 846e1b8..aec5a5a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1507,7 +1507,8 @@ static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-static void update_super_roots(struct btrfs_root *root)
+static void update_super_roots(struct btrfs_trans_handle *trans,
+			       struct btrfs_root *root)
 {
 	struct btrfs_root_item *root_item;
 	struct btrfs_super_block *super;
@@ -1523,7 +1524,7 @@ static void update_super_roots(struct btrfs_root *root)
 	super->root = root_item->bytenr;
 	super->generation = root_item->generation;
 	super->root_level = root_item->level;
-	if (btrfs_test_opt(root, SPACE_CACHE))
+	if (btrfs_test_trans_opt(trans, SPACE_CACHE))
 		super->cache_generation = root_item->generation;
 	if (root->fs_info->update_uuid_tree_gen)
 		super->uuid_tree_generation = root_item->generation;
@@ -1987,7 +1988,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	switch_commit_roots(cur_trans, root->fs_info);
 
 	assert_qgroups_uptodate(trans);
-	update_super_roots(root);
+	update_super_roots(trans, root);
 
 	btrfs_set_super_log_root(root->fs_info->super_copy, 0);
 	btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
-- 
2.2.2

[PATCH v4 4/8] btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE if it's under transaction protect.

[Qu Wenruo]

Convert btrfs_test_opt() to btrfs_test_trans_opt() if it's called under
transaction protection.

This will ensure SPACE_CACHE bit is consistent during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/ctree.h            | 1 -
 fs/btrfs/disk-io.c          | 4 ----
 fs/btrfs/free-space-cache.c | 2 +-
 fs/btrfs/inode-map.c        | 5 +++--
 fs/btrfs/transaction.c      | 9 ---------
 5 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5f99743..f72acf5 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2108,7 +2108,6 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
 #define BTRFS_MOUNT_RESCAN_UUID_TREE	(1 << 23)
-#define	BTRFS_MOUNT_CHANGE_INODE_CACHE	(1 << 24)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(8192)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2d3c8b7..f4d168d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2832,10 +2832,6 @@ retry_root_backup:
 		btrfs_set_opt(fs_info->mount_opt, SSD);
 	}
 
-	/* Set the real inode map cache flag */
-	if (btrfs_test_opt(tree_root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(tree_root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
 		ret = btrfsic_mount(tree_root, fs_devices,
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index d6c03f7..2b9cabf 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3348,7 +3348,7 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
 	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
 	int ret;
 
-	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+	if (!btrfs_test_trans_opt(trans, INODE_MAP_CACHE))
 		return 0;
 
 	ret = __btrfs_write_out_cache(root, inode, ctl, NULL, trans, path, 0);
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 81efd83..49b089c 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -178,7 +178,8 @@ static void start_caching(struct btrfs_root *root)
 			  root->root_key.objectid);
 	if (IS_ERR(tsk)) {
 		btrfs_warn(root->fs_info, "failed to start inode caching task");
-		btrfs_clear_and_info(root, CHANGE_INODE_CACHE,
+		btrfs_clear_and_info(root->fs_info, root->fs_info->mount_opt,
+				INODE_MAP_CACHE,
 				"disabling inode map caching");
 	}
 }
@@ -405,7 +406,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	if (btrfs_root_refs(&root->root_item) == 0)
 		return 0;
 
-	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+	if (!btrfs_test_trans_opt(trans, INODE_MAP_CACHE))
 		return 0;
 
 	path = btrfs_alloc_path();
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index aec5a5a..dd9e7af 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1939,15 +1939,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 		goto scrub_continue;
 	}
 
-	/*
-	 * Since the transaction is done, we should set the inode map cache flag
-	 * before any other comming transaction.
-	 */
-	if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-	else
-		btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 	/* commit_fs_roots gets rid of all the tree log roots, it is now
 	 * safe to free the root of tree log roots
 	 */
-- 
2.2.2

[PATCH v4 4/8] btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under transaction protect.

[Qu Wenruo]

Convert btrfs_test_opt() to btrfs_test_trans_opt() if it's called under
transaction protection.
This will ensure SPACE_CACHE bit is consistent during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/extent-tree.c | 2 +-
 fs/btrfs/transaction.c | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1511658..c968d12 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3260,7 +3260,7 @@ again:
 
 	spin_lock(&block_group->lock);
 	if (block_group->cached != BTRFS_CACHE_FINISHED ||
-	    !btrfs_test_opt(root, SPACE_CACHE) ||
+	    !btrfs_test_trans_opt(trans, SPACE_CACHE) ||
 	    block_group->delalloc_bytes) {
 		/*
 		 * don't bother trying to write stuff out _if_
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 846e1b8..aec5a5a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1507,7 +1507,8 @@ static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-static void update_super_roots(struct btrfs_root *root)
+static void update_super_roots(struct btrfs_trans_handle *trans,
+			       struct btrfs_root *root)
 {
 	struct btrfs_root_item *root_item;
 	struct btrfs_super_block *super;
@@ -1523,7 +1524,7 @@ static void update_super_roots(struct btrfs_root *root)
 	super->root = root_item->bytenr;
 	super->generation = root_item->generation;
 	super->root_level = root_item->level;
-	if (btrfs_test_opt(root, SPACE_CACHE))
+	if (btrfs_test_trans_opt(trans, SPACE_CACHE))
 		super->cache_generation = root_item->generation;
 	if (root->fs_info->update_uuid_tree_gen)
 		super->uuid_tree_generation = root_item->generation;
@@ -1987,7 +1988,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	switch_commit_roots(cur_trans, root->fs_info);
 
 	assert_qgroups_uptodate(trans);
-	update_super_roots(root);
+	update_super_roots(trans, root);
 
 	btrfs_set_super_log_root(root->fs_info->super_copy, 0);
 	btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
-- 
2.2.2

[PATCH v4 5/8] btrfs: Make btrfs_parse_options() parse mount option in a atomic way

[Qu Wenruo]

Current btrfs_parse_options() is not atomic, which can set and clear a
bit, especially for nospace_cache case.

For example, if a fs is mounted with nospace_cache,
btrfs_parse_options() will set SPACE_CACHE bit first(since
cache_generation is non-zeo) and clear the SPACE_CACHE bit due to
nospace_cache mount option.
So under heavy operations and remount a nospace_cache btrfs, there is a
windows for commit to create space cache.

This bug can be reproduced by fstest/btrfs/071 073 074 with
nospace_cache mount option. It has about 50% chance to create space
cache, and about 10% chance to create wrong space cache, which can't
pass btrfsck.

This patch will do the mount option parse in a copy-and-update method.
First copy the mount_opt from fs_info to new_opt, and only update
options in new_opt. At last, copy the new_opt back to
fs_info->mount_opt.

This patch is already good enough to fix the above nospace_cache +
remount bug, but need later patch to make sure mount options does not
change during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/ctree.h |  16 ++++----
 fs/btrfs/super.c | 115 +++++++++++++++++++++++++++++--------------------------
 2 files changed, 69 insertions(+), 62 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f72acf5..fa04db9 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2118,18 +2118,18 @@ struct btrfs_ioctl_defrag_range_args {
 #define btrfs_test_opt(root, opt)	((root)->fs_info->mount_opt & \
 					 BTRFS_MOUNT_##opt)
 
-#define btrfs_set_and_info(root, opt, fmt, args...)			\
+#define btrfs_set_and_info(fs_info, val, opt, fmt, args...)		\
 {									\
-	if (!btrfs_test_opt(root, opt))					\
-		btrfs_info(root->fs_info, fmt, ##args);			\
-	btrfs_set_opt(root->fs_info->mount_opt, opt);			\
+	if (!btrfs_raw_test_opt(val, opt))				\
+		btrfs_info(fs_info, fmt, ##args);			\
+	btrfs_set_opt(val, opt);					\
 }
 
-#define btrfs_clear_and_info(root, opt, fmt, args...)			\
+#define btrfs_clear_and_info(fs_info, val, opt, fmt, args...)		\
 {									\
-	if (btrfs_test_opt(root, opt))					\
-		btrfs_info(root->fs_info, fmt, ##args);			\
-	btrfs_clear_opt(root->fs_info->mount_opt, opt);			\
+	if (btrfs_raw_test_opt(val, opt))				\
+		btrfs_info(fs_info, fmt, ##args);			\
+	btrfs_clear_opt(val, opt);					\
 }
 
 /*
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b0c45b2..490fe1f 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -395,10 +395,13 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 	int ret = 0;
 	char *compress_type;
 	bool compress_force = false;
+	unsigned long new_opt;
+
+	new_opt = info->mount_opt;
 
 	cache_gen = btrfs_super_cache_generation(root->fs_info->super_copy);
 	if (cache_gen)
-		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+		btrfs_set_opt(new_opt, SPACE_CACHE);
 
 	if (!options)
 		goto out;
@@ -422,7 +425,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		switch (token) {
 		case Opt_degraded:
 			btrfs_info(root->fs_info, "allowing degraded mounts");
-			btrfs_set_opt(info->mount_opt, DEGRADED);
+			btrfs_set_opt(new_opt, DEGRADED);
 			break;
 		case Opt_subvol:
 		case Opt_subvolid:
@@ -434,7 +437,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			 */
 			break;
 		case Opt_nodatasum:
-			btrfs_set_and_info(root, NODATASUM,
+			btrfs_set_and_info(info, new_opt, NODATASUM,
 					   "setting nodatasum");
 			break;
 		case Opt_datasum:
@@ -444,8 +447,8 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				else
 					btrfs_info(root->fs_info, "setting datasum");
 			}
-			btrfs_clear_opt(info->mount_opt, NODATACOW);
-			btrfs_clear_opt(info->mount_opt, NODATASUM);
+			btrfs_clear_opt(new_opt, NODATACOW);
+			btrfs_clear_opt(new_opt, NODATASUM);
 			break;
 		case Opt_nodatacow:
 			if (!btrfs_test_opt(root, NODATACOW)) {
@@ -457,13 +460,13 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 					btrfs_info(root->fs_info, "setting nodatacow");
 				}
 			}
-			btrfs_clear_opt(info->mount_opt, COMPRESS);
-			btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
-			btrfs_set_opt(info->mount_opt, NODATACOW);
-			btrfs_set_opt(info->mount_opt, NODATASUM);
+			btrfs_clear_opt(new_opt, COMPRESS);
+			btrfs_clear_opt(new_opt, FORCE_COMPRESS);
+			btrfs_set_opt(new_opt, NODATACOW);
+			btrfs_set_opt(new_opt, NODATASUM);
 			break;
 		case Opt_datacow:
-			btrfs_clear_and_info(root, NODATACOW,
+			btrfs_clear_and_info(info, new_opt, NODATACOW,
 					     "setting datacow");
 			break;
 		case Opt_compress_force:
@@ -477,20 +480,20 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			    strcmp(args[0].from, "zlib") == 0) {
 				compress_type = "zlib";
 				info->compress_type = BTRFS_COMPRESS_ZLIB;
-				btrfs_set_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, NODATACOW);
-				btrfs_clear_opt(info->mount_opt, NODATASUM);
+				btrfs_set_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, NODATACOW);
+				btrfs_clear_opt(new_opt, NODATASUM);
 			} else if (strcmp(args[0].from, "lzo") == 0) {
 				compress_type = "lzo";
 				info->compress_type = BTRFS_COMPRESS_LZO;
-				btrfs_set_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, NODATACOW);
-				btrfs_clear_opt(info->mount_opt, NODATASUM);
+				btrfs_set_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, NODATACOW);
+				btrfs_clear_opt(new_opt, NODATASUM);
 				btrfs_set_fs_incompat(info, COMPRESS_LZO);
 			} else if (strncmp(args[0].from, "no", 2) == 0) {
 				compress_type = "no";
-				btrfs_clear_opt(info->mount_opt, COMPRESS);
-				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
+				btrfs_clear_opt(new_opt, COMPRESS);
+				btrfs_clear_opt(new_opt, FORCE_COMPRESS);
 				compress_force = false;
 			} else {
 				ret = -EINVAL;
@@ -498,7 +501,8 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			}
 
 			if (compress_force) {
-				btrfs_set_and_info(root, FORCE_COMPRESS,
+				btrfs_set_and_info(info, new_opt,
+						   FORCE_COMPRESS,
 						   "force %s compression",
 						   compress_type);
 			} else {
@@ -512,29 +516,29 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				 * flag, otherwise, there is no way for users
 				 * to disable forcible compression separately.
 				 */
-				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
+				btrfs_clear_opt(new_opt, FORCE_COMPRESS);
 			}
 			break;
 		case Opt_ssd:
-			btrfs_set_and_info(root, SSD,
+			btrfs_set_and_info(info, new_opt, SSD,
 					   "use ssd allocation scheme");
 			break;
 		case Opt_ssd_spread:
-			btrfs_set_and_info(root, SSD_SPREAD,
+			btrfs_set_and_info(info, new_opt, SSD_SPREAD,
 					   "use spread ssd allocation scheme");
-			btrfs_set_opt(info->mount_opt, SSD);
+			btrfs_set_opt(new_opt, SSD);
 			break;
 		case Opt_nossd:
-			btrfs_set_and_info(root, NOSSD,
-					     "not using ssd allocation scheme");
-			btrfs_clear_opt(info->mount_opt, SSD);
+			btrfs_set_and_info(info, new_opt, NOSSD,
+					   "not using ssd allocation scheme");
+			btrfs_clear_opt(new_opt, SSD);
 			break;
 		case Opt_barrier:
-			btrfs_clear_and_info(root, NOBARRIER,
+			btrfs_clear_and_info(info, new_opt, NOBARRIER,
 					     "turning on barriers");
 			break;
 		case Opt_nobarrier:
-			btrfs_set_and_info(root, NOBARRIER,
+			btrfs_set_and_info(info, new_opt, NOBARRIER,
 					   "turning off barriers");
 			break;
 		case Opt_thread_pool:
@@ -594,19 +598,19 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 			break;
 		case Opt_notreelog:
-			btrfs_set_and_info(root, NOTREELOG,
+			btrfs_set_and_info(info, new_opt, NOTREELOG,
 					   "disabling tree log");
 			break;
 		case Opt_treelog:
-			btrfs_clear_and_info(root, NOTREELOG,
+			btrfs_clear_and_info(info, new_opt, NOTREELOG,
 					     "enabling tree log");
 			break;
 		case Opt_flushoncommit:
-			btrfs_set_and_info(root, FLUSHONCOMMIT,
+			btrfs_set_and_info(info, new_opt, FLUSHONCOMMIT,
 					   "turning on flush-on-commit");
 			break;
 		case Opt_noflushoncommit:
-			btrfs_clear_and_info(root, FLUSHONCOMMIT,
+			btrfs_clear_and_info(info, new_opt, FLUSHONCOMMIT,
 					     "turning off flush-on-commit");
 			break;
 		case Opt_ratio:
@@ -623,71 +627,71 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			}
 			break;
 		case Opt_discard:
-			btrfs_set_and_info(root, DISCARD,
+			btrfs_set_and_info(info, new_opt, DISCARD,
 					   "turning on discard");
 			break;
 		case Opt_nodiscard:
-			btrfs_clear_and_info(root, DISCARD,
+			btrfs_clear_and_info(info, new_opt, DISCARD,
 					     "turning off discard");
 			break;
 		case Opt_space_cache:
-			btrfs_set_and_info(root, SPACE_CACHE,
+			btrfs_set_and_info(info, new_opt, SPACE_CACHE,
 					   "enabling disk space caching");
 			break;
 		case Opt_rescan_uuid_tree:
-			btrfs_set_opt(info->mount_opt, RESCAN_UUID_TREE);
+			btrfs_set_opt(new_opt, RESCAN_UUID_TREE);
 			break;
 		case Opt_no_space_cache:
-			btrfs_clear_and_info(root, SPACE_CACHE,
+			btrfs_clear_and_info(info, new_opt, SPACE_CACHE,
 					     "disabling disk space caching");
 			break;
 		case Opt_inode_cache:
-			btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
+			btrfs_set_and_info(info, new_opt, INODE_MAP_CACHE,
 					   "enabling inode map caching");
 			break;
 		case Opt_noinode_cache:
-			btrfs_clear_pending_and_info(info, INODE_MAP_CACHE,
+			btrfs_clear_and_info(info, new_opt, INODE_MAP_CACHE,
 					     "disabling inode map caching");
 			break;
 		case Opt_clear_cache:
-			btrfs_set_and_info(root, CLEAR_CACHE,
+			btrfs_set_and_info(info, new_opt, CLEAR_CACHE,
 					   "force clearing of disk cache");
 			break;
 		case Opt_user_subvol_rm_allowed:
-			btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
+			btrfs_set_opt(new_opt, USER_SUBVOL_RM_ALLOWED);
 			break;
 		case Opt_enospc_debug:
-			btrfs_set_opt(info->mount_opt, ENOSPC_DEBUG);
+			btrfs_set_opt(new_opt, ENOSPC_DEBUG);
 			break;
 		case Opt_noenospc_debug:
-			btrfs_clear_opt(info->mount_opt, ENOSPC_DEBUG);
+			btrfs_clear_opt(new_opt, ENOSPC_DEBUG);
 			break;
 		case Opt_defrag:
-			btrfs_set_and_info(root, AUTO_DEFRAG,
+			btrfs_set_and_info(info, new_opt, AUTO_DEFRAG,
 					   "enabling auto defrag");
 			break;
 		case Opt_nodefrag:
-			btrfs_clear_and_info(root, AUTO_DEFRAG,
+			btrfs_clear_and_info(info, new_opt, AUTO_DEFRAG,
 					     "disabling auto defrag");
 			break;
 		case Opt_recovery:
 			btrfs_info(root->fs_info, "enabling auto recovery");
-			btrfs_set_opt(info->mount_opt, RECOVERY);
+			btrfs_set_opt(new_opt, RECOVERY);
 			break;
 		case Opt_skip_balance:
-			btrfs_set_opt(info->mount_opt, SKIP_BALANCE);
+			btrfs_set_opt(new_opt, SKIP_BALANCE);
 			break;
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 		case Opt_check_integrity_including_extent_data:
 			btrfs_info(root->fs_info,
 				   "enabling check integrity including extent data");
-			btrfs_set_opt(info->mount_opt,
+			btrfs_set_opt(new_opt,
 				      CHECK_INTEGRITY_INCLUDING_EXTENT_DATA);
-			btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
+			btrfs_set_opt(new_opt, CHECK_INTEGRITY);
 			break;
 		case Opt_check_integrity:
 			btrfs_info(root->fs_info, "enabling check integrity");
-			btrfs_set_opt(info->mount_opt, CHECK_INTEGRITY);
+			btrfs_set_opt(new_opt, CHECK_INTEGRITY);
 			break;
 		case Opt_check_integrity_print_mask:
 			ret = match_int(&args[0], &intarg);
@@ -713,10 +717,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 #endif
 		case Opt_fatal_errors:
 			if (strcmp(args[0].from, "panic") == 0)
-				btrfs_set_opt(info->mount_opt,
+				btrfs_set_opt(new_opt,
 					      PANIC_ON_FATAL_ERROR);
 			else if (strcmp(args[0].from, "bug") == 0)
-				btrfs_clear_opt(info->mount_opt,
+				btrfs_clear_opt(new_opt,
 					      PANIC_ON_FATAL_ERROR);
 			else {
 				ret = -EINVAL;
@@ -752,8 +756,11 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		}
 	}
 out:
-	if (!ret && btrfs_test_opt(root, SPACE_CACHE))
-		btrfs_info(root->fs_info, "disk space caching is enabled");
+	if (!ret) {
+		if (btrfs_raw_test_opt(new_opt, SPACE_CACHE))
+			btrfs_info(info, "disk space caching is enabled");
+		info->mount_opt = new_opt;
+	}
 	kfree(orig);
 	return ret;
 }
-- 
2.2.2

[PATCH v4 5/8] btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE if it's under transaction protect.

[Qu Wenruo]

Convert btrfs_test_opt() to btrfs_test_trans_opt() if it's called under
transaction protection.

This will ensure SPACE_CACHE bit is consistent during transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/ctree.h            | 1 -
 fs/btrfs/disk-io.c          | 4 ----
 fs/btrfs/free-space-cache.c | 2 +-
 fs/btrfs/inode-map.c        | 5 +++--
 fs/btrfs/transaction.c      | 9 ---------
 5 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 26bb47b..fa04db9 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2108,7 +2108,6 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
 #define BTRFS_MOUNT_RESCAN_UUID_TREE	(1 << 23)
-#define	BTRFS_MOUNT_CHANGE_INODE_CACHE	(1 << 24)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(8192)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2d3c8b7..f4d168d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2832,10 +2832,6 @@ retry_root_backup:
 		btrfs_set_opt(fs_info->mount_opt, SSD);
 	}
 
-	/* Set the real inode map cache flag */
-	if (btrfs_test_opt(tree_root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(tree_root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
 		ret = btrfsic_mount(tree_root, fs_devices,
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index d6c03f7..2b9cabf 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3348,7 +3348,7 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
 	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
 	int ret;
 
-	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+	if (!btrfs_test_trans_opt(trans, INODE_MAP_CACHE))
 		return 0;
 
 	ret = __btrfs_write_out_cache(root, inode, ctl, NULL, trans, path, 0);
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 81efd83..49b089c 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -178,7 +178,8 @@ static void start_caching(struct btrfs_root *root)
 			  root->root_key.objectid);
 	if (IS_ERR(tsk)) {
 		btrfs_warn(root->fs_info, "failed to start inode caching task");
-		btrfs_clear_and_info(root, CHANGE_INODE_CACHE,
+		btrfs_clear_and_info(root->fs_info, root->fs_info->mount_opt,
+				INODE_MAP_CACHE,
 				"disabling inode map caching");
 	}
 }
@@ -405,7 +406,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	if (btrfs_root_refs(&root->root_item) == 0)
 		return 0;
 
-	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+	if (!btrfs_test_trans_opt(trans, INODE_MAP_CACHE))
 		return 0;
 
 	path = btrfs_alloc_path();
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index aec5a5a..dd9e7af 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1939,15 +1939,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 		goto scrub_continue;
 	}
 
-	/*
-	 * Since the transaction is done, we should set the inode map cache flag
-	 * before any other comming transaction.
-	 */
-	if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
-		btrfs_set_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-	else
-		btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
-
 	/* commit_fs_roots gets rid of all the tree log roots, it is now
 	 * safe to free the root of tree log roots
 	 */
-- 
2.2.2

[PATCH v4 6/8] vfs: Add get_vfsmount_sb() function to get vfsmount from a given sb.

[Qu Wenruo]

There are sysfs interfaces in some fs, only btrfs yet, which will modify
on-disk data.
Unlike normal file operation routine we can use mnt_want_write_file() to
protect the operation, change through sysfs won't to be binded to any file
in the filesystem.
So we can only extract the first vfsmount of a superblock and pass it to
mnt_want_write() to do the protection.

Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/namespace.c        | 25 +++++++++++++++++++++++++
 include/linux/mount.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index cd1e968..5a16a62 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1105,6 +1105,31 @@ struct vfsmount *mntget(struct vfsmount *mnt)
 }
 EXPORT_SYMBOL(mntget);
 
+/*
+ * get a vfsmount from a given sb
+ *
+ * This is especially used for case where change fs' sysfs interface
+ * will lead to a write, e.g. Change label through sysfs in btrfs.
+ * So vfs can get a vfsmount and then use mnt_want_write() to protect.
+ */
+struct vfsmount *get_vfsmount_sb(struct super_block *sb)
+{
+	struct vfsmount *ret_vfs = NULL;
+	struct mount *mnt;
+	int ret = 0;
+
+	lock_mount_hash();
+	if (list_empty(&sb->s_mounts))
+		goto out;
+	mnt = list_entry(sb->s_mounts.next, struct mount, mnt_instance);
+	ret_vfs = &mnt->mnt;
+	ret_vfs = mntget(ret_vfs);
+out:
+	unlock_mount_hash();
+	return ret_vfs;
+}
+EXPORT_SYMBOL(get_vfsmount_sb);
+
 struct vfsmount *mnt_clone_internal(struct path *path)
 {
 	struct mount *p;
diff --git a/include/linux/mount.h b/include/linux/mount.h
index c2c561d..cf1b0f5 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -79,6 +79,7 @@ extern void mnt_drop_write_file(struct file *file);
 extern void mntput(struct vfsmount *mnt);
 extern struct vfsmount *mntget(struct vfsmount *mnt);
 extern struct vfsmount *mnt_clone_internal(struct path *path);
+extern struct vfsmount *get_vfsmount_sb(struct super_block *sb);
 extern int __mnt_is_readonly(struct vfsmount *mnt);
 
 struct path;
-- 
2.2.2

[PATCH v4 7/8] btrfs: Use mnt_want_write() to protect label change.

[Qu Wenruo]

Use the new vfs API get_vfsmount_sb() to get a vfsmount and use it to
do the write protection of the label change transaction.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/sysfs.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index b2e7bb4..cdfa6b9 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -25,6 +25,7 @@
 #include <linux/bug.h>
 #include <linux/genhd.h>
 #include <linux/debugfs.h>
+#include <linux/mount.h>
 
 #include "ctree.h"
 #include "disk-io.h"
@@ -374,11 +375,10 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = fs_info->fs_root;
+	struct vfsmount *vfsmount;
 	int ret;
 	size_t p_len;
 
-	if (fs_info->sb->s_flags & MS_RDONLY)
-		return -EROFS;
 
 	/*
 	 * p_len is the len until the first occurrence of either
@@ -389,9 +389,21 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 	if (p_len >= BTRFS_LABEL_SIZE)
 		return -EINVAL;
 
+	vfsmount = get_vfsmount_sb(fs_info->sb);
+	if (!vfsmount)
+		return -EINVAL;
+
+	ret = mnt_want_write(vfsmount);
+	if (ret) {
+		mntput(vfsmount);
+		return ret;
+	}
+
 	trans = btrfs_start_transaction(root, 0);
-	if (IS_ERR(trans))
-		return PTR_ERR(trans);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out;
+	}
 
 	spin_lock(&root->fs_info->super_lock);
 	memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
@@ -399,9 +411,11 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
 	spin_unlock(&root->fs_info->super_lock);
 	ret = btrfs_commit_transaction(trans, root);
 
+out:
+	mnt_drop_write(vfsmount);
+	mntput(vfsmount);
 	if (!ret)
 		return len;
-
 	return ret;
 }
 BTRFS_ATTR_RW(label, btrfs_label_show, btrfs_label_store);
-- 
2.2.2

[PATCH v4 8/8] btrfs: Use mnt_want_write() to protect sysfs feature change.

[Qu Wenruo]

Just like label change, use mnt_want_write() to do a correct protection.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/sysfs.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index cdfa6b9..71e50ba 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -113,6 +113,7 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_feature_attr *fa = to_btrfs_feature_attr(a);
 	struct btrfs_trans_handle *trans;
+	struct vfsmount *vfsmount;
 	u64 features, set, clear;
 	unsigned long val;
 	int ret;
@@ -154,9 +155,20 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 	btrfs_info(fs_info, "%s %s feature flag",
 		   val ? "Setting" : "Clearing", fa->kobj_attr.attr.name);
 
+	vfsmount = get_vfsmount_sb(fs_info->sb);
+	if (!vfsmount)
+		return -EINVAL;
+
+	ret = mnt_want_write(vfsmount);
+	if (ret) {
+		mntput(vfsmount);
+		return ret;
+	}
 	trans = btrfs_start_transaction(fs_info->fs_root, 0);
-	if (IS_ERR(trans))
-		return PTR_ERR(trans);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out;
+	}
 
 	spin_lock(&fs_info->super_lock);
 	features = get_features(fs_info, fa->feature_set);
@@ -168,10 +180,13 @@ static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
 	spin_unlock(&fs_info->super_lock);
 
 	ret = btrfs_commit_transaction(trans, fs_info->fs_root);
-	if (ret)
-		return ret;
 
-	return count;
+out:
+	mnt_drop_write(vfsmount);
+	mntput(vfsmount);
+	if (!ret)
+		return count;
+	return ret;
 }
 
 static umode_t btrfs_feature_visible(struct kobject *kobj,
-- 
2.2.2

Re: [PATCH v4 0/8] Fix freeze/sysfs deadlock in better method.

[Qu Wenruo]

Oh, I'm very sorry for the patchset which includes other 
unrelated/out-of-date patches.

I'll resend them with correct patchese.

Thanks,
Qu
-------- Original Message --------
Subject: [PATCH v4 0/8] Fix freeze/sysfs deadlock in better method.
From: Qu Wenruo <quwenruo@cn.fujitsu.com>
To: <linux-btrfs@vger.kernel.org>
Date: 2015年01月29日 09:27
> Patchset to solve the previous found freeze/sysfs deadlock.
>
> Unlike previous pending_changes, which uses transaction commits to
> ensure mount option doesn't change during transaction.
> This idea is great in concept, but will introduce extra and somewhat
> duplicated ro/freeze check, and the original synchronized behavior is
> also changed.
>
> [Per-transaction mount option]
> This patch use the RCU-like concept, which will copy the mount_opt from
> fs_info into btrfs_transaction, and each btrfs_test_opt() for specific
> mount option bit(SPACE_CACHE/INODE_MAP_CACHE) should be changed to
> btrfs_test_trans_opt().
> So mount option during transaction won't be changed, and also, no extra
> read_only or freeze check is needed, the commit routine is also
> untouched.
>
> [Use VFS protect for sysfs change]
> The 6th patch will introduce a new help function get_vfsmount_sb() to
> get a vfsmount from a sb, with this vfsmount, we can use vfs level
> mnt_want_write() to do a comprehensive protection other than the cheap
> ro/freeze check.
>
> Qu Wenruo (8):
>    Revert "btrfs: add support for processing pending changes" related
>      commits
>    btrfs: Make btrfs_parse_options() parse mount option in a atomic way
>    btrfs: Introduce per-transaction mount_opt to keep mount option
>      consistent during transaction.
>    btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under
>         transaction protect.
>    btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE if it's under
>         transaction protect.
>    vfs: Add get_vfsmount_sb() function to get vfsmount from a given sb.
>    btrfs: Use mnt_want_write() to protect label change.
>    btrfs: Use mnt_want_write() to protect sysfs feature change.
>
>   fs/btrfs/ctree.h            |  64 +++-------------------
>   fs/btrfs/disk-io.c          |   6 ---
>   fs/btrfs/extent-tree.c      |   2 +-
>   fs/btrfs/free-space-cache.c |   2 +-
>   fs/btrfs/inode-map.c        |   5 +-
>   fs/btrfs/super.c            | 129 ++++++++++++++++++++++----------------------
>   fs/btrfs/sysfs.c            |  73 ++++++++++++++++++-------
>   fs/btrfs/transaction.c      |  43 ++-------------
>   fs/btrfs/transaction.h      |   6 ++-
>   fs/namespace.c              |  25 +++++++++
>   include/linux/mount.h       |   1 +
>   11 files changed, 167 insertions(+), 189 deletions(-)
>