Btrfs: add a delalloc mutex to inodes for delalloc reservations

I was using i_mutex for this, but we're getting bogus lockdep warnings by doing
that and theres no real way to get rid of those, so just stop using i_mutex to
protect delalloc metadata reservations and use a delalloc mutex instead.  This
shouldn't be contended often at all, only if you are writing and mmap writing to
the file at the same time.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 556f9aa25bb7..e0ad5f0f895e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4345,12 +4345,11 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
         /* Need to be holding the i_mutex here if we aren't free space cache */
         if (btrfs_is_free_space_inode(root, inode))
                 flush = 0;
-        else
-                WARN_ON(!mutex_is_locked(&inode->i_mutex));
 
         if (flush && btrfs_transaction_in_commit(root->fs_info))
                 schedule_timeout(1);
 
+        mutex_lock(&BTRFS_I(inode)->delalloc_mutex);
         num_bytes = ALIGN(num_bytes, root->sectorsize);
 
         spin_lock(&BTRFS_I(inode)->lock);
@@ -4405,6 +4404,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
                                                       btrfs_ino(inode),
                                                       to_free, 0);
                 }
+                mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
                 return ret;
         }
 
@@ -4415,6 +4415,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
         }
         BTRFS_I(inode)->reserved_extents += nr_extents;
         spin_unlock(&BTRFS_I(inode)->lock);
+        mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
 
         if (to_reserve)
                 trace_btrfs_space_reservation(root->fs_info,"delalloc",