Hi!

On 01/16/2017 02:58 PM, Junxiao Bi wrote:
On 01/16/2017 02:42 PM, Eric Ren wrote:
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().

Changes since v1:
1. Let ocfs2_is_locked_by_me() just return true/false to indicate if the
process gets the cluster lock - suggested by: Joseph Qi <jiangqi...@gmail.com>
and Junxiao Bi <junxiao...@oracle.com>.

2. Change "struct ocfs2_holder" to a more meaningful name "ocfs2_lock_holder",
suggested by: Junxiao Bi <junxiao...@oracle.com>.

3. Add debugging output at ocfs2_setattr() and ocfs2_permission() to
catch exceptional cases, suggested by: Junxiao Bi <junxiao...@oracle.com>.

Signed-off-by: Eric Ren <z...@suse.com>
---
  fs/ocfs2/acl.c  | 39 +++++++++++++++++++++++++----
  fs/ocfs2/file.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++--------
  2 files changed, 100 insertions(+), 15 deletions(-)

diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index bed1fcb..3e47262 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -284,16 +284,31 @@ int ocfs2_iop_set_acl(struct inode *inode, struct 
posix_acl *acl, int type)
  {
        struct buffer_head *bh = NULL;
        int status = 0;
-
-       status = ocfs2_inode_lock(inode, &bh, 1);
+       int arg_flags = 0, has_locked;
+       struct ocfs2_lock_holder oh;
+       struct ocfs2_lock_res *lockres;
+
+       lockres = &OCFS2_I(inode)->ip_inode_lockres;
+       has_locked = ocfs2_is_locked_by_me(lockres);
+       if (has_locked)
+               arg_flags = OCFS2_META_LOCK_GETBH;
+       status = ocfs2_inode_lock_full(inode, &bh, 1, arg_flags);
        if (status < 0) {
                if (status != -ENOENT)
                        mlog_errno(status);
                return status;
        }
+       if (!has_locked)
+               ocfs2_add_holder(lockres, &oh);
+
Same code pattern showed here and *get_acl, can it be abstracted to one
function?
The same issue for *setattr and *permission. Sorry for not mention that
in last review.

Good idea! I will do it in the next version;-)

Thanks,
Eric


Thanks,
Junxiao.
        status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);
-       ocfs2_inode_unlock(inode, 1);
+
+       if (!has_locked) {
+               ocfs2_remove_holder(lockres, &oh);
+               ocfs2_inode_unlock(inode, 1);
+       }
        brelse(bh);
+
        return status;
  }
@@ -303,21 +318,35 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
        struct buffer_head *di_bh = NULL;
        struct posix_acl *acl;
        int ret;
+       int arg_flags = 0, has_locked;
+       struct ocfs2_lock_holder oh;
+       struct ocfs2_lock_res *lockres;
osb = OCFS2_SB(inode->i_sb);
        if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
                return NULL;
-       ret = ocfs2_inode_lock(inode, &di_bh, 0);
+
+       lockres = &OCFS2_I(inode)->ip_inode_lockres;
+       has_locked = ocfs2_is_locked_by_me(lockres);
+       if (has_locked)
+               arg_flags = OCFS2_META_LOCK_GETBH;
+       ret = ocfs2_inode_lock_full(inode, &di_bh, 0, arg_flags);
        if (ret < 0) {
                if (ret != -ENOENT)
                        mlog_errno(ret);
                return ERR_PTR(ret);
        }
+       if (!has_locked)
+               ocfs2_add_holder(lockres, &oh);
acl = ocfs2_get_acl_nolock(inode, type, di_bh); - ocfs2_inode_unlock(inode, 0);
+       if (!has_locked) {
+               ocfs2_remove_holder(lockres, &oh);
+               ocfs2_inode_unlock(inode, 0);
+       }
        brelse(di_bh);
+
        return acl;
  }
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index c488965..b620c25 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1138,6 +1138,9 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr 
*attr)
        handle_t *handle = NULL;
        struct dquot *transfer_to[MAXQUOTAS] = { };
        int qtype;
+       int arg_flags = 0, had_lock;
+       struct ocfs2_lock_holder oh;
+       struct ocfs2_lock_res *lockres;
trace_ocfs2_setattr(inode, dentry,
                            (unsigned long long)OCFS2_I(inode)->ip_blkno,
@@ -1173,13 +1176,41 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr 
*attr)
                }
        }
- status = ocfs2_inode_lock(inode, &bh, 1);
+       lockres = &OCFS2_I(inode)->ip_inode_lockres;
+       had_lock = ocfs2_is_locked_by_me(lockres);
+       if (had_lock) {
+               arg_flags = OCFS2_META_LOCK_GETBH;
+
+               /*
+                * 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();
+       }
+       status = ocfs2_inode_lock_full(inode, &bh, 1, arg_flags);
        if (status < 0) {
                if (status != -ENOENT)
                        mlog_errno(status);
                goto bail_unlock_rw;
        }
-       inode_locked = 1;
+       if (!had_lock) {
+               ocfs2_add_holder(lockres, &oh);
+               inode_locked = 1;
+       }
if (size_change) {
                status = inode_newsize_ok(inode, attr->ia_size);
@@ -1260,7 +1291,8 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr 
*attr)
  bail_commit:
        ocfs2_commit_trans(osb, handle);
  bail_unlock:
-       if (status) {
+       if (status && inode_locked) {
+               ocfs2_remove_holder(lockres, &oh);
                ocfs2_inode_unlock(inode, 1);
                inode_locked = 0;
        }
@@ -1278,8 +1310,10 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr 
*attr)
                if (status < 0)
                        mlog_errno(status);
        }
-       if (inode_locked)
+       if (inode_locked) {
+               ocfs2_remove_holder(lockres, &oh);
                ocfs2_inode_unlock(inode, 1);
+       }
brelse(bh);
        return status;
@@ -1321,20 +1355,42 @@ int ocfs2_getattr(struct vfsmount *mnt,
  int ocfs2_permission(struct inode *inode, int mask)
  {
        int ret;
+       int has_locked;
+       struct ocfs2_lock_holder oh;
+       struct ocfs2_lock_res *lockres;
if (mask & MAY_NOT_BLOCK)
                return -ECHILD;
- ret = ocfs2_inode_lock(inode, NULL, 0);
-       if (ret) {
-               if (ret != -ENOENT)
-                       mlog_errno(ret);
-               goto out;
+       lockres = &OCFS2_I(inode)->ip_inode_lockres;
+       has_locked = ocfs2_is_locked_by_me(lockres);
+       if (!has_locked) {
+               ret = ocfs2_inode_lock(inode, NULL, 0);
+               if (ret) {
+                       if (ret != -ENOENT)
+                               mlog_errno(ret);
+                       goto out;
+               }
+               ocfs2_add_holder(lockres, &oh);
+       } else {
+               /* 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);
+       if (!has_locked) {
+               ocfs2_remove_holder(lockres, &oh);
+               ocfs2_inode_unlock(inode, 0);
+       }
  out:
        return ret;
  }



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