diff options
authorJeff Mahoney <jeffm@suse.com>2013-05-31 15:51:17 -0400
committerJan Kara <jack@suse.cz>2013-05-31 23:14:20 +0200
commita1457c0ce976bad1356b9b0437f2a5c3ab8a9cfc (patch)
parent4a8570112b76a63ad21cfcbe2783f98f7fd5ba1b (diff)
reiserfs: fix deadlock with nfs racing on create/lookup
Reiserfs is currently able to be deadlocked by having two NFS clients where one has removed and recreated a file and another is accessing the file with an open file handle. If one client deletes and recreates a file with timing such that the recreated file obtains the same [dirid, objectid] pair as the original file while another client accesses the file via file handle, the create and lookup can race and deadlock if the lookup manages to create the in-memory inode first. The create thread, in insert_inode_locked4, will hold the write lock while waiting on the other inode to be unlocked. The lookup thread, anywhere in the iget path, will release and reacquire the write lock while it schedules. If it needs to reacquire the lock while the create thread has it, it will never be able to make forward progress because it needs to reacquire the lock before ultimately unlocking the inode. This patch drops the write lock across the insert_inode_locked4 call so that the ordering of inode_wait -> write lock is retained. Since this would have been the case before the BKL push-down, this is safe. Signed-off-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Jan Kara <jack@suse.cz>
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index 77d6d47abc8..f844533792e 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -1811,11 +1811,16 @@ int reiserfs_new_inode(struct reiserfs_transaction_handle *th,
memcpy(INODE_PKEY(inode), &(ih.ih_key), KEY_SIZE);
args.dirid = le32_to_cpu(ih.ih_key.k_dir_id);
- if (insert_inode_locked4(inode, args.objectid,
- reiserfs_find_actor, &args) < 0) {
+ reiserfs_write_unlock(inode->i_sb);
+ err = insert_inode_locked4(inode, args.objectid,
+ reiserfs_find_actor, &args);
+ reiserfs_write_lock(inode->i_sb);
+ if (err) {
err = -EINVAL;
goto out_bad_inode;
if (old_format_only(sb))
/* not a perfect generation count, as object ids can be reused, but
** this is as good as reiserfs can do right now.