From fede766f28dd766d4e8feb321fdb19edb21ef6fb Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Fri, 27 Apr 2012 14:23:22 -0400
Subject: [PATCH] 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>
---
fs/btrfs/inode.c | 30 +-----------------------------
1 file changed, 1 insertion(+), 29 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d953f8820464..3ce7805d1117 100644
--- 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.
*
--
2.34.1