Btrfs: avoid deadlocks from GFP_KERNEL allocations during btrfs_real_readdir

Btrfs has an optimization where it will preallocate dentries during
readdir to fill in enough information to open the inode without an extra
lookup.

But, we're calling d_alloc, which is doing GFP_KERNEL allocations, and
that leads to deadlocks because our readdir code has tree locks held.

For now, disable this optimization.  We'll fix the gfp mask in the next
merge window.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d953f8820464e40f95b2c992ab25f648b890289a..3ce7805d1117eedf36cd3338543e7209474fba7f 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4192,7 +4192,6 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
        struct btrfs_path *path;
        struct list_head ins_list;
        struct list_head del_list;
-       struct qstr q;
        int ret;
        struct extent_buffer *leaf;
        int slot;
@@ -4283,7 +4282,6 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
 
                while (di_cur < di_total) {
                        struct btrfs_key location;
-                       struct dentry *tmp;
 
                        if (verify_dir_item(root, leaf, di))
                                break;
@@ -4304,33 +4302,7 @@ static int btrfs_real_readdir(struct file *filp, void *dirent,
                        d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
                        btrfs_dir_item_key_to_cpu(leaf, di, &location);
 
-                       q.name = name_ptr;
-                       q.len = name_len;
-                       q.hash = full_name_hash(q.name, q.len);
-                       tmp = d_lookup(filp->f_dentry, &q);
-                       if (!tmp) {
-                               struct btrfs_key *newkey;
-
-                               newkey = kzalloc(sizeof(struct btrfs_key),
-                                                GFP_NOFS);
-                               if (!newkey)
-                                       goto no_dentry;
-                               tmp = d_alloc(filp->f_dentry, &q);
-                               if (!tmp) {
-                                       kfree(newkey);
-                                       dput(tmp);
-                                       goto no_dentry;
-                               }
-                               memcpy(newkey, &location,
-                                      sizeof(struct btrfs_key));
-                               tmp->d_fsdata = newkey;
-                               tmp->d_flags |= DCACHE_NEED_LOOKUP;
-                               d_rehash(tmp);
-                               dput(tmp);
-                       } else {
-                               dput(tmp);
-                       }
-no_dentry:
+
                        /* is this a reference to our own snapshot? If so
                         * skip it.
                         *