jiangyiwen
2014-Jun-13 08:51 UTC
[Ocfs2-devel] [patch V2] ocfs2: fix a tiny race when running dirop_fileop_racer
When running dirop_fileop_racer we found a dead lock case.
2 nodes, say Node A and Node B, mount the same ocfs2 volume. Create
/race/16/1 in the filesystem, and let the inode number of dir 16 is less
than the inode number of dir race.
Node A Node B
mv /race/16/1 /race/
right after Node A has got the
EX mode of /race/16/, and tries to
get EX mode of /race
ls /race/16/
In this case, Node A has got the EX mode of /race/16/, and wants to get EX
mode of /race/. Node B has got the PR mode of /race/, and wants to get
the PR mode of /race/16/. Since EX and PR are mutually exclusive, dead
lock happens.
This patch fixes this case by locking in ancestor order before trying
inode number order.
Signed-off-by: Yiwen Jiang <jiangyiwen at huawei.com>
Signed-off-by: Joseph Qi <joseph.qi at huawei.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
fs/ocfs2/namei.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++--
fs/ocfs2/ocfs2_trace.h | 2 ++
2 files changed, 96 insertions(+), 2 deletions(-)
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 2060fc3..7011f9e 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -991,6 +991,65 @@ leave:
return status;
}
+static int ocfs2_check_if_ancestor(struct ocfs2_super *osb,
+ u64 src_inode_no, u64 dest_inode_no)
+{
+ int ret = 0, i = 0;
+ u64 parent_inode_no = 0;
+ u64 child_inode_no = src_inode_no;
+ struct inode *child_inode;
+
+#define MAX_LOOKUP_TIMES 32
+ while (1) {
+ child_inode = ocfs2_iget(osb, child_inode_no, 0, 0);
+ if (IS_ERR(child_inode)) {
+ ret = PTR_ERR(child_inode);
+ break;
+ }
+
+ ret = ocfs2_inode_lock(child_inode, NULL, 0);
+ if (ret < 0) {
+ iput(child_inode);
+ if (ret != -ENOENT)
+ mlog_errno(ret);
+ break;
+ }
+
+ ret = ocfs2_lookup_ino_from_name(child_inode, "..", 2,
+ &parent_inode_no);
+ ocfs2_inode_unlock(child_inode, 0);
+ iput(child_inode);
+ if (ret < 0) {
+ ret = -ENOENT;
+ break;
+ }
+
+ if (parent_inode_no == dest_inode_no) {
+ ret = 1;
+ break;
+ }
+
+ if (parent_inode_no == osb->root_inode->i_ino) {
+ ret = 0;
+ break;
+ }
+
+ child_inode_no = parent_inode_no;
+
+ if (++i >= MAX_LOOKUP_TIMES) {
+ mlog(ML_NOTICE, "max lookup times reached, filesystem "
+ "may have nested directories, "
+ "src inode: %llu, dest inode: %llu.\n",
+ (unsigned long long)src_inode_no,
+ (unsigned long long)dest_inode_no);
+ ret = 0;
+ break;
+ }
+ }
+
+ return ret;
+}
+
/*
* The only place this should be used is rename!
* if they have the same id, then the 1st one is the only one locked.
@@ -1002,6 +1061,7 @@ static int ocfs2_double_lock(struct ocfs2_super *osb,
struct inode *inode2)
{
int status;
+ int inode1_is_ancestor, inode2_is_ancestor;
struct ocfs2_inode_info *oi1 = OCFS2_I(inode1);
struct ocfs2_inode_info *oi2 = OCFS2_I(inode2);
struct buffer_head **tmpbh;
@@ -1015,9 +1075,26 @@ static int ocfs2_double_lock(struct ocfs2_super *osb,
if (*bh2)
*bh2 = NULL;
- /* we always want to lock the one with the lower lockid first. */
+ /* we always want to lock the one with the lower lockid first.
+ * and if they are nested, we lock ancestor first */
if (oi1->ip_blkno != oi2->ip_blkno) {
- if (oi1->ip_blkno < oi2->ip_blkno) {
+ inode1_is_ancestor = ocfs2_check_if_ancestor(osb, oi2->ip_blkno,
+ oi1->ip_blkno);
+ if (inode1_is_ancestor < 0) {
+ status = inode1_is_ancestor;
+ goto bail;
+ }
+
+ inode2_is_ancestor = ocfs2_check_if_ancestor(osb, oi1->ip_blkno,
+ oi2->ip_blkno);
+ if (inode2_is_ancestor < 0) {
+ status = inode2_is_ancestor;
+ goto bail;
+ }
+
+ if ((inode1_is_ancestor == 1) ||
+ (oi1->ip_blkno < oi2->ip_blkno &&
+ inode2_is_ancestor == 0)) {
/* switch id1 and id2 around */
tmpbh = bh2;
bh2 = bh1;
@@ -1134,6 +1211,21 @@ static int ocfs2_rename(struct inode *old_dir,
goto bail;
}
rename_lock = 1;
+
+ /* here we cannot guarantee the inodes haven't just been
+ * changed, so check if they are nested again */
+ status = ocfs2_check_if_ancestor(osb, new_dir->i_ino,
+ old_inode->i_ino);
+ if (status < 0) {
+ mlog_errno(status);
+ goto bail;
+ } else if (status == 1) {
+ status = -EPERM;
+ trace_ocfs2_rename_not_permitted(
+ (unsigned long long)old_inode->i_ino,
+ (unsigned long long)new_dir->i_ino);
+ goto bail;
+ }
}
/* if old and new are the same, this'll just do one lock. */
diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h
index 1b60c62..6cb019b 100644
--- a/fs/ocfs2/ocfs2_trace.h
+++ b/fs/ocfs2/ocfs2_trace.h
@@ -2292,6 +2292,8 @@ TRACE_EVENT(ocfs2_rename,
__entry->new_len, __get_str(new_name))
);
+DEFINE_OCFS2_ULL_ULL_EVENT(ocfs2_rename_not_permitted);
+
TRACE_EVENT(ocfs2_rename_target_exists,
TP_PROTO(int new_len, const char *new_name),
TP_ARGS(new_len, new_name),
--
1.8.4.3
Mark Fasheh
2014-Jun-13 21:19 UTC
[Ocfs2-devel] [patch V2] ocfs2: fix a tiny race when running dirop_fileop_racer
On Fri, Jun 13, 2014 at 04:51:33PM +0800, jiangyiwen wrote:> When running dirop_fileop_racer we found a dead lock case. > > 2 nodes, say Node A and Node B, mount the same ocfs2 volume. Create > /race/16/1 in the filesystem, and let the inode number of dir 16 is less > than the inode number of dir race. > > Node A Node B > mv /race/16/1 /race/ > right after Node A has got the > EX mode of /race/16/, and tries to > get EX mode of /race > ls /race/16/ > > In this case, Node A has got the EX mode of /race/16/, and wants to get EX > mode of /race/. Node B has got the PR mode of /race/, and wants to get > the PR mode of /race/16/. Since EX and PR are mutually exclusive, dead > lock happens. > > This patch fixes this case by locking in ancestor order before trying > inode number order. > > Signed-off-by: Yiwen Jiang <jiangyiwen at huawei.com> > Signed-off-by: Joseph Qi <joseph.qi at huawei.com> > Signed-off-by: Andrew Morton <akpm at linux-foundation.org>Reviewed-by: Mark Fasheh <mfasheh at suse.de> --Mark -- Mark Fasheh