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>

5 files changed, 7 insertions, 16 deletions

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 634608d2a6d0..9b9b15fd5204 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -51,6 +51,9 @@ struct btrfs_inode {
         /* held while logging the inode in tree-log.c */
         struct mutex log_mutex;
 
+        /* held while doing delalloc reservations */
+        struct mutex delalloc_mutex;
+
         /* used to order data wrt metadata */
         struct btrfs_ordered_inode_tree ordered_tree;
 
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",
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 619742d37166..5977987abdb1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2239,14 +2239,7 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
                                 continue;
                         }
                         nr_truncate++;
-                        /*
-                         * Need to hold the imutex for reservation purposes, not
-                         * a huge deal here but I have a WARN_ON in
-                         * btrfs_delalloc_reserve_space to catch offenders.
-                         */
-                        mutex_lock(&inode->i_mutex);
                         ret = btrfs_truncate(inode);
-                        mutex_unlock(&inode->i_mutex);
                 } else {
                         nr_unlink++;
                 }
@@ -6411,10 +6404,7 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
         u64 page_start;
         u64 page_end;
 
-        /* Need this to keep space reservations serialized */
-        mutex_lock(&inode->i_mutex);
         ret  = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
-        mutex_unlock(&inode->i_mutex);
         if (!ret)
                 ret = btrfs_update_time(vma->vm_file);
         if (ret) {
@@ -6758,6 +6748,7 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
         extent_io_tree_init(&ei->io_tree, &inode->i_data);
         extent_io_tree_init(&ei->io_failure_tree, &inode->i_data);
         mutex_init(&ei->log_mutex);
+        mutex_init(&ei->delalloc_mutex);
         btrfs_ordered_inode_tree_init(&ei->ordered_tree);
         INIT_LIST_HEAD(&ei->i_orphan);
         INIT_LIST_HEAD(&ei->delalloc_inodes);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7fdf22c2dc0d..6834be4c8709 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -868,10 +868,8 @@ static int cluster_pages_for_defrag(struct inode *inode,
                 return 0;
         file_end = (isize - 1) >> PAGE_CACHE_SHIFT;
 
-        mutex_lock(&inode->i_mutex);
         ret = btrfs_delalloc_reserve_space(inode,
                                            num_pages << PAGE_CACHE_SHIFT);
-        mutex_unlock(&inode->i_mutex);
         if (ret)
                 return ret;
 again:
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index efe9f792544d..8c1aae2c845d 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2949,9 +2949,7 @@ static int relocate_file_extent_cluster(struct inode *inode,
         index = (cluster->start - offset) >> PAGE_CACHE_SHIFT;
         last_index = (cluster->end - offset) >> PAGE_CACHE_SHIFT;
         while (index <= last_index) {
-                mutex_lock(&inode->i_mutex);
                 ret = btrfs_delalloc_reserve_metadata(inode, PAGE_CACHE_SIZE);
-                mutex_unlock(&inode->i_mutex);
                 if (ret)
                         goto out;