On 01/06/2017 02:09 PM, Joseph Qi wrote:
Hi Eric,


On 17/1/5 23:31, 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().
As described cases above, shall we just add the tracking logic only for 
set/get_acl()?

The idea is to detect recursive locking on the running task stack. Take case 1) for example if ocfs2_permisssion()
is not changed:

ocfs2_permission() <=== take PR, ocfs2_holder is not added
   ocfs2_iop_get_acl <=== still take PR, because there is no lock holder on the 
tracking list

Thanks for your review;-)
Eric


Thanks,
Joseph

Signed-off-by: Eric Ren <z...@suse.com>
---
  fs/ocfs2/acl.c  | 39 ++++++++++++++++++++++++++++++++++-----
  fs/ocfs2/file.c | 44 ++++++++++++++++++++++++++++++++++----------
  2 files changed, 68 insertions(+), 15 deletions(-)

diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index bed1fcb..c539890 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_holder oh;
+    struct ocfs2_lock_res *lockres;
+
+    lockres = &OCFS2_I(inode)->ip_inode_lockres;
+    has_locked = (ocfs2_is_locked_by_me(lockres) != NULL);
+    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);
+
      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_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) != NULL);
+    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..62be75d 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_holder oh;
+    struct ocfs2_lock_res *lockres;
        trace_ocfs2_setattr(inode, dentry,
                  (unsigned long long)OCFS2_I(inode)->ip_blkno,
@@ -1173,13 +1176,20 @@ 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) != NULL);
+    if (had_lock)
+        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);
          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 +1270,8 @@ 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 +1289,10 @@ 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 +1334,31 @@ int ocfs2_getattr(struct vfsmount *mnt,
  int ocfs2_permission(struct inode *inode, int mask)
  {
      int ret;
+    int has_locked;
+    struct ocfs2_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) != NULL);
+    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);
      }
        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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