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>

1 files changed, 16 insertions, 6 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 115d1646bf50..faff98f720de 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3227,12 +3227,14 @@ static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
         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 @@ u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags)
 
 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 @@ static void clear_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
         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,