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, 1 insertions, 10 deletions

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);