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Btrfs: avoid deadlocks from GFP_KERNEL allocations during btrfs_real_readdir

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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>
This commit is contained in:
Chris Mason 2012-04-27 14:23:22 -04:00
parent 7654b72417
commit fede766f28
1 changed files with 0 additions and 28 deletions
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28
fs/btrfs/inode.c
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@ -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.
*