commit de98ced9e743656d108de41841797def0f5cb951
author Miao Xie <miaox@cn.fujitsu.com> Tue Jan 29 10:13:12 2013 +0000
committer Josef Bacik <jbacik@fusionio.com> Wed Feb 20 12:59:08 2013 -0500
tree 52314be4abe2cd2510712e8b629d58d8d01d5e0a
parent df0af1a57f72c74d53a9377c60ff20095afab97d

Btrfs: use seqlock to protect fs_info->avail_{data, metadata, system}_alloc_bits

There is no lock to protect
  fs_info->avail_{data, metadata, system}_alloc_bits,
it may introduce some problem, such as the wrong profile
information, so we add a seqlock to protect them.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/extent-tree.c

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 115d164..faff98f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3227,12 +3227,14 @@
 	u64 extra_flags = chunk_to_extended(flags) &
 				BTRFS_EXTENDED_PROFILE_MASK;
 
+	write_seqlock(&fs_info->profiles_lock);
 	if (flags & BTRFS_BLOCK_GROUP_DATA)
 		fs_info->avail_data_alloc_bits |= extra_flags;
 	if (flags & BTRFS_BLOCK_GROUP_METADATA)
 		fs_info->avail_metadata_alloc_bits |= extra_flags;
 	if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
 		fs_info->avail_system_alloc_bits |= extra_flags;
+	write_sequnlock(&fs_info->profiles_lock);
 }
 
 /*
@@ -3324,12 +3326,18 @@
 
 static u64 get_alloc_profile(struct btrfs_root *root, u64 flags)
 {
-	if (flags & BTRFS_BLOCK_GROUP_DATA)
-		flags |= root->fs_info->avail_data_alloc_bits;
-	else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
-		flags |= root->fs_info->avail_system_alloc_bits;
-	else if (flags & BTRFS_BLOCK_GROUP_METADATA)
-		flags |= root->fs_info->avail_metadata_alloc_bits;
+	unsigned seq;
+
+	do {
+		seq = read_seqbegin(&root->fs_info->profiles_lock);
+
+		if (flags & BTRFS_BLOCK_GROUP_DATA)
+			flags |= root->fs_info->avail_data_alloc_bits;
+		else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
+			flags |= root->fs_info->avail_system_alloc_bits;
+		else if (flags & BTRFS_BLOCK_GROUP_METADATA)
+			flags |= root->fs_info->avail_metadata_alloc_bits;
+	} while (read_seqretry(&root->fs_info->profiles_lock, seq));
 
 	return btrfs_reduce_alloc_profile(root, flags);
 }
@@ -7967,12 +7975,14 @@
 	u64 extra_flags = chunk_to_extended(flags) &
 				BTRFS_EXTENDED_PROFILE_MASK;
 
+	write_seqlock(&fs_info->profiles_lock);
 	if (flags & BTRFS_BLOCK_GROUP_DATA)
 		fs_info->avail_data_alloc_bits &= ~extra_flags;
 	if (flags & BTRFS_BLOCK_GROUP_METADATA)
 		fs_info->avail_metadata_alloc_bits &= ~extra_flags;
 	if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
 		fs_info->avail_system_alloc_bits &= ~extra_flags;
+	write_sequnlock(&fs_info->profiles_lock);
 }
 
 int btrfs_remove_block_group(struct btrfs_trans_handle *trans,