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From: Miao Xie <miaox@cn.fujitsu.com>
To: Linux Btrfs <linux-btrfs@vger.kernel.org>
Subject: [PATCH V2 02/10] Btrfs: use atomic for fs_info->last_trans_committed
Date: Tue, 29 Jan 2013 18:00:34 +0800	[thread overview]
Message-ID: <51079DC2.8090600@cn.fujitsu.com> (raw)
In-Reply-To: <51079D72.7000301@cn.fujitsu.com>

fs_info->last_trans_committed is a 64bit variant, and it can be
accessed by multi-task, if there is no lock or other methods to
protect it, we might get the wrong number, especially on 32bit
machine.(Even on 64bit machine, it is possible that the compiler
may split a 64bit operation into two 32bit operation.)

For example, Assuming ->last_trans_committed is 0x00000000ffffffff
at the beginning, then we want set it to 0x0000000100000000.
	Task0			Task1
	set low 32 bits
				load low 32 bits
				load high 32 bits
	set high 32 bits

The task will get 0, it is a wrong number.

We fix this problem by the atomic operation.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
Changelog v1 -> v2:
- modify the changelog and make it more clear and stringency.
---
 fs/btrfs/ctree.h        |  2 +-
 fs/btrfs/disk-io.c      |  2 +-
 fs/btrfs/file.c         |  2 +-
 fs/btrfs/ioctl.c        |  2 +-
 fs/btrfs/ordered-data.c |  2 +-
 fs/btrfs/scrub.c        |  2 +-
 fs/btrfs/transaction.c  |  5 +++--
 fs/btrfs/tree-log.c     | 16 +++++++++-------
 8 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c3edb22..34a60a8 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1279,7 +1279,7 @@ struct btrfs_fs_info {
 	struct btrfs_block_rsv empty_block_rsv;
 
 	atomic64_t generation;
-	u64 last_trans_committed;
+	atomic64_t last_trans_committed;
 
 	/*
 	 * this is updated to the current trans every time a full commit
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f03aebc..87ed05a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2502,7 +2502,7 @@ retry_root_backup:
 	}
 
 	atomic64_set(&fs_info->generation, generation);
-	fs_info->last_trans_committed = generation;
+	atomic64_set(&fs_info->last_trans_committed, generation);
 
 	ret = btrfs_recover_balance(fs_info);
 	if (ret) {
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 02409b6..910ea99 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1683,7 +1683,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	if (btrfs_inode_in_log(inode,
 	    atomic64_read(&root->fs_info->generation)) ||
 	    BTRFS_I(inode)->last_trans <=
-	    root->fs_info->last_trans_committed) {
+	    atomic64_read(&root->fs_info->last_trans_committed)) {
 		BTRFS_I(inode)->last_trans = 0;
 
 		/*
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index afbf3ac..3b6c339 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3114,7 +3114,7 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
 			return PTR_ERR(trans);
 
 		/* No running transaction, don't bother */
-		transid = root->fs_info->last_trans_committed;
+		transid = atomic64_read(&root->fs_info->last_trans_committed);
 		goto out;
 	}
 	transid = trans->transid;
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index f107312..f376621 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -975,7 +975,7 @@ void btrfs_add_ordered_operation(struct btrfs_trans_handle *trans,
 	 * if this file hasn't been changed since the last transaction
 	 * commit, we can safely return without doing anything
 	 */
-	if (last_mod < root->fs_info->last_trans_committed)
+	if (last_mod < atomic64_read(&root->fs_info->last_trans_committed))
 		return;
 
 	spin_lock(&root->fs_info->ordered_extent_lock);
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index bdbb94f..af0b566 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2703,7 +2703,7 @@ static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
 	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
 		return -EIO;
 
-	gen = root->fs_info->last_trans_committed;
+	gen = atomic64_read(&root->fs_info->last_trans_committed);
 
 	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
 		bytenr = btrfs_sb_offset(i);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 105d642..29fdf1c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -459,7 +459,8 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
 	int ret = 0;
 
 	if (transid) {
-		if (transid <= root->fs_info->last_trans_committed)
+		if (transid <=
+		    atomic64_read(&root->fs_info->last_trans_committed))
 			goto out;
 
 		ret = -EINVAL;
@@ -1730,7 +1731,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
 	cur_trans->commit_done = 1;
 
-	root->fs_info->last_trans_committed = cur_trans->transid;
+	atomic64_set(&root->fs_info->last_trans_committed, cur_trans->transid);
 
 	wake_up(&cur_trans->commit_wait);
 
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 9027bb1..7f42a53 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3397,7 +3397,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
 	INIT_LIST_HEAD(&extents);
 
 	write_lock(&tree->lock);
-	test_gen = root->fs_info->last_trans_committed;
+	test_gen = atomic64_read(&root->fs_info->last_trans_committed);
 
 	list_for_each_entry_safe(em, n, &tree->modified_extents, list) {
 		list_del_init(&em->list);
@@ -3502,7 +3502,8 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
 
 	/* Only run delayed items if we are a dir or a new file */
 	if (S_ISDIR(inode->i_mode) ||
-	    BTRFS_I(inode)->generation > root->fs_info->last_trans_committed) {
+	    BTRFS_I(inode)->generation >
+	    atomic64_read(&root->fs_info->last_trans_committed)) {
 		ret = btrfs_commit_inode_delayed_items(trans, inode);
 		if (ret) {
 			btrfs_free_path(path);
@@ -3744,7 +3745,8 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 	struct super_block *sb;
 	struct dentry *old_parent = NULL;
 	int ret = 0;
-	u64 last_committed = root->fs_info->last_trans_committed;
+	u64 last_committed = atomic64_read(
+			     &root->fs_info->last_trans_committed);
 
 	sb = inode->i_sb;
 
@@ -3754,7 +3756,7 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 	}
 
 	if (root->fs_info->last_trans_log_full_commit >
-	    root->fs_info->last_trans_committed) {
+	    atomic64_read(&root->fs_info->last_trans_committed)) {
 		ret = 1;
 		goto end_no_trans;
 	}
@@ -3806,7 +3808,7 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 			break;
 
 		if (BTRFS_I(inode)->generation >
-		    root->fs_info->last_trans_committed) {
+		    atomic64_read(&root->fs_info->last_trans_committed)) {
 			ret = btrfs_log_inode(trans, root, inode, inode_only);
 			if (ret)
 				goto end_trans;
@@ -4069,9 +4071,9 @@ int btrfs_log_new_name(struct btrfs_trans_handle *trans,
 	 * from hasn't been logged, we don't need to log it
 	 */
 	if (BTRFS_I(inode)->logged_trans <=
-	    root->fs_info->last_trans_committed &&
+	    atomic64_read(&root->fs_info->last_trans_committed) &&
 	    (!old_dir || BTRFS_I(old_dir)->logged_trans <=
-		    root->fs_info->last_trans_committed))
+		    atomic64_read(&root->fs_info->last_trans_committed)))
 		return 0;
 
 	return btrfs_log_inode_parent(trans, root, inode, parent, 1);
-- 
1.7.11.7


  reply	other threads:[~2013-01-29  9:59 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-29  9:59 [PATCH V2 01/10] Btrfs: use atomic for btrfs_fs_info->generation Miao Xie
2013-01-29 10:00 ` Miao Xie [this message]
2013-01-29 10:03 ` [PATCH V2 03/10] Btrfs: use atomic for fs_info->last_trans_log_full_commit Miao Xie
2013-01-29 10:05 ` [PATCH V2 04/10] Btrfs: add a comment for fs_info->max_inline Miao Xie
2013-01-29 10:07 ` [PATCH V2 05/10] Btrfs: protect fs_info->alloc_start Miao Xie
2013-01-29 10:09 ` [PATCH V2 06/10] Btrfs: use percpu counter for dirty metadata count Miao Xie
2013-01-29 10:10 ` [PATCH V2 07/10] Btrfs: use percpu counter for fs_info->delalloc_bytes Miao Xie
2013-01-29 10:11 ` [PATCH V2 08/10] Btrfs: use the inode own lock to protect its delalloc_bytes Miao Xie
2013-01-29 10:13 ` [PATCH V2 09/10] Btrfs: use seqlock to protect fs_info->avail_{data, metadata, system}_alloc_bits Miao Xie
2013-01-29 10:14 ` [PATCH V2 10/10] Btrfs: use bit operation for ->fs_state Miao Xie

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