[PATCH 3.10 028/268] ocfs2: fix BUG_ON() in ocfs2_ci_checkpointed()

From: Willy Tarreau
Date: Mon Jun 19 2017 - 15:35:50 EST

From: Tariq Saeed <tariq.x.saeed@xxxxxxxxxx>

commit 3d46a44a0c01b15d385ccaae24b56f619613c256 upstream.

PID: 614 TASK: ffff882a739da580 CPU: 3 COMMAND: "ocfs2dc"
#0 [ffff882ecc3759b0] machine_kexec at ffffffff8103b35d
#1 [ffff882ecc375a20] crash_kexec at ffffffff810b95b5
#2 [ffff882ecc375af0] oops_end at ffffffff815091d8
#3 [ffff882ecc375b20] die at ffffffff8101868b
#4 [ffff882ecc375b50] do_trap at ffffffff81508bb0
#5 [ffff882ecc375ba0] do_invalid_op at ffffffff810165e5
#6 [ffff882ecc375c40] invalid_op at ffffffff815116fb
[exception RIP: ocfs2_ci_checkpointed+208]
RIP: ffffffffa0a7e940 RSP: ffff882ecc375cf0 RFLAGS: 00010002
RAX: 0000000000000001 RBX: 000000000000654b RCX: ffff8812dc83f1f8
RDX: 00000000000017d9 RSI: ffff8812dc83f1f8 RDI: ffffffffa0b2c318
RBP: ffff882ecc375d20 R8: ffff882ef6ecfa60 R9: ffff88301f272200
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffffffffff
R13: ffff8812dc83f4f0 R14: 0000000000000000 R15: ffff8812dc83f1f8
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#7 [ffff882ecc375d28] ocfs2_check_meta_downconvert at ffffffffa0a7edbd [ocfs2]
#8 [ffff882ecc375d38] ocfs2_unblock_lock at ffffffffa0a84af8 [ocfs2]
#9 [ffff882ecc375dc8] ocfs2_process_blocked_lock at ffffffffa0a85285 [ocfs2]
assert is tripped because the tran is not checkpointed and the lock level is PR.

Some time ago, chmod command had been executed. As result, the following call
chain left the inode cluster lock in PR state, latter on causing the assert.
system_call_fastpath
-> my_chmod
-> sys_chmod
-> sys_fchmodat
-> notify_change
-> ocfs2_setattr
-> posix_acl_chmod
-> ocfs2_iop_set_acl
-> ocfs2_set_acl
-> ocfs2_acl_set_mode
Here is how.
1119 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
1120 {
1247 ocfs2_inode_unlock(inode, 1); <<< WRONG thing to do.
..
1258 if (!status && attr->ia_valid & ATTR_MODE) {
1259 status = posix_acl_chmod(inode, inode->i_mode);

519 posix_acl_chmod(struct inode *inode, umode_t mode)
520 {
..
539 ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);

287 int ocfs2_iop_set_acl(struct inode *inode, struct posix_acl *acl, ...
288 {
289 return ocfs2_set_acl(NULL, inode, NULL, type, acl, NULL, NULL);

224 int ocfs2_set_acl(handle_t *handle,
225 struct inode *inode, ...
231 {
..
252 ret = ocfs2_acl_set_mode(inode, di_bh,
253 handle, mode);

168 static int ocfs2_acl_set_mode(struct inode *inode, struct buffer_head ...
170 {
183 if (handle == NULL) {
>>> BUG: inode lock not held in ex at this point <<<
184 handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb),
185 OCFS2_INODE_UPDATE_CREDITS);

ocfs2_setattr.#1247 we unlock and at #1259 call posix_acl_chmod. When we reach
ocfs2_acl_set_mode.#181 and do trans, the inode cluster lock is not held in EX
mode (it should be). How this could have happended?

We are the lock master, were holding lock EX and have released it in
ocfs2_setattr.#1247. Note that there are no holders of this lock at
this point. Another node needs the lock in PR, and we downconvert from
EX to PR. So the inode lock is PR when do the trans in
ocfs2_acl_set_mode.#184. The trans stays in core (not flushed to disc).
Now another node want the lock in EX, downconvert thread gets kicked
(the one that tripped assert abovt), finds an unflushed trans but the
lock is not EX (it is PR). If the lock was at EX, it would have flushed
the trans ocfs2_ci_checkpointed -> ocfs2_start_checkpoint before
downconverting (to NULL) for the request.

ocfs2_setattr must not drop inode lock ex in this code path. If it
does, takes it again before the trans, say in ocfs2_set_acl, another
cluster node can get in between, execute another setattr, overwriting
the one in progress on this node, resulting in a mode acl size combo
that is a mix of the two.

Orabug: 20189959
Signed-off-by: Tariq Saeed <tariq.x.saeed@xxxxxxxxxx>
Reviewed-by: Mark Fasheh <mfasheh@xxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Joseph Qi <joseph.qi@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
fs/ocfs2/file.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 496af7f..86ed0f4 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1104,6 +1104,7 @@ out:
int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
{
int status = 0, size_change;
+ int inode_locked = 0;
struct inode *inode = dentry->d_inode;
struct super_block *sb = inode->i_sb;
struct ocfs2_super *osb = OCFS2_SB(sb);
@@ -1149,6 +1150,7 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
mlog_errno(status);
goto bail_unlock_rw;
}
+ inode_locked = 1;

if (size_change && attr->ia_size != i_size_read(inode)) {
status = inode_newsize_ok(inode, attr->ia_size);
@@ -1229,7 +1231,10 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
bail_commit:
ocfs2_commit_trans(osb, handle);
bail_unlock:
- ocfs2_inode_unlock(inode, 1);
+ if (status) {
+ ocfs2_inode_unlock(inode, 1);
+ inode_locked = 0;
+ }
bail_unlock_rw:
if (size_change)
ocfs2_rw_unlock(inode, 1);
@@ -1245,6 +1250,8 @@ bail:
if (status < 0)
mlog_errno(status);
}
+ if (inode_locked)
+ ocfs2_inode_unlock(inode, 1);

return status;
}
--
2.8.0.rc2.1.gbe9624a