ocfs2: fix deadlock issue when taking inode lock at vfs entry points
Commit 743b5f1434f5 ("ocfs2: take inode lock in ocfs2_iop_set/get_acl()")
results in a deadlock, as the author "Tariq Saeed" realized shortly
after the patch was merged. The discussion happened here
https://oss.oracle.com/pipermail/ocfs2-devel/2015-September/011085.html
The reason why taking cluster inode lock at vfs entry points opens up a
self deadlock window, is explained in the previous patch of this series.
So far, we have seen two different code paths that have this issue.
1. do_sys_open
may_open
inode_permission
ocfs2_permission
ocfs2_inode_lock() <=== take PR
generic_permission
get_acl
ocfs2_iop_get_acl
ocfs2_inode_lock() <=== take PR
2. fchmod|fchmodat
chmod_common
notify_change
ocfs2_setattr <=== take EX
posix_acl_chmod
get_acl
ocfs2_iop_get_acl <=== take PR
ocfs2_iop_set_acl <=== take EX
Fixes them by adding the tracking logic (in the previous patch) for these
funcs above, ocfs2_permission(), ocfs2_iop_[set|get]_acl(),
ocfs2_setattr().
Link: http://lkml.kernel.org/r/20170117100948.11657-3-zren@suse.com
Signed-off-by: Eric Ren <zren@suse.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Joseph Qi <jiangqi903@gmail.com>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index c488965..7b6a146 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1138,6 +1138,8 @@
handle_t *handle = NULL;
struct dquot *transfer_to[MAXQUOTAS] = { };
int qtype;
+ int had_lock;
+ struct ocfs2_lock_holder oh;
trace_ocfs2_setattr(inode, dentry,
(unsigned long long)OCFS2_I(inode)->ip_blkno,
@@ -1173,11 +1175,30 @@
}
}
- status = ocfs2_inode_lock(inode, &bh, 1);
- if (status < 0) {
- if (status != -ENOENT)
- mlog_errno(status);
+ had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);
+ if (had_lock < 0) {
+ status = had_lock;
goto bail_unlock_rw;
+ } else if (had_lock) {
+ /*
+ * As far as we know, ocfs2_setattr() could only be the first
+ * VFS entry point in the call chain of recursive cluster
+ * locking issue.
+ *
+ * For instance:
+ * chmod_common()
+ * notify_change()
+ * ocfs2_setattr()
+ * posix_acl_chmod()
+ * ocfs2_iop_get_acl()
+ *
+ * But, we're not 100% sure if it's always true, because the
+ * ordering of the VFS entry points in the call chain is out
+ * of our control. So, we'd better dump the stack here to
+ * catch the other cases of recursive locking.
+ */
+ mlog(ML_ERROR, "Another case of recursive locking:\n");
+ dump_stack();
}
inode_locked = 1;
@@ -1260,8 +1281,8 @@
bail_commit:
ocfs2_commit_trans(osb, handle);
bail_unlock:
- if (status) {
- ocfs2_inode_unlock(inode, 1);
+ if (status && inode_locked) {
+ ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
inode_locked = 0;
}
bail_unlock_rw:
@@ -1279,7 +1300,7 @@
mlog_errno(status);
}
if (inode_locked)
- ocfs2_inode_unlock(inode, 1);
+ ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
brelse(bh);
return status;
@@ -1320,21 +1341,32 @@
int ocfs2_permission(struct inode *inode, int mask)
{
- int ret;
+ int ret, had_lock;
+ struct ocfs2_lock_holder oh;
if (mask & MAY_NOT_BLOCK)
return -ECHILD;
- ret = ocfs2_inode_lock(inode, NULL, 0);
- if (ret) {
- if (ret != -ENOENT)
- mlog_errno(ret);
+ had_lock = ocfs2_inode_lock_tracker(inode, NULL, 0, &oh);
+ if (had_lock < 0) {
+ ret = had_lock;
goto out;
+ } else if (had_lock) {
+ /* See comments in ocfs2_setattr() for details.
+ * The call chain of this case could be:
+ * do_sys_open()
+ * may_open()
+ * inode_permission()
+ * ocfs2_permission()
+ * ocfs2_iop_get_acl()
+ */
+ mlog(ML_ERROR, "Another case of recursive locking:\n");
+ dump_stack();
}
ret = generic_permission(inode, mask);
- ocfs2_inode_unlock(inode, 0);
+ ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);
out:
return ret;
}