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Message-Id: <20170117063054.30519-3-zren@suse.com>
Date: Tue, 17 Jan 2017 14:30:54 +0800
From: Eric Ren <zren@...e.com>
To: ocfs2-devel@....oracle.com
Cc: akpm@...ux-foundation.org, mfasheh@...sity.com, jlbec@...lplan.org,
ghe@...e.com, junxiao.bi@...cle.com, jiangqi903@...il.com,
sfr@...b.auug.org.au, hch@....de, linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/2] 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().
Changes since v1:
- Let ocfs2_is_locked_by_me() just return true/false to indicate if the
process gets the cluster lock - suggested by: Joseph Qi <jiangqi903@...il.com>
and Junxiao Bi <junxiao.bi@...cle.com>.
- Change "struct ocfs2_holder" to a more meaningful name "ocfs2_lock_holder",
suggested by: Junxiao Bi.
- Add debugging output at ocfs2_setattr() and ocfs2_permission() to
catch exceptional cases, suggested by: Junxiao Bi.
Changes since v2:
- Use new wrappers of tracking logic code, suggested by: Junxiao Bi.
Signed-off-by: Eric Ren <zren@...e.com>
---
fs/ocfs2/acl.c | 29 +++++++++++++----------------
fs/ocfs2/file.c | 58 ++++++++++++++++++++++++++++++++++++++++++++-------------
2 files changed, 58 insertions(+), 29 deletions(-)
diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index bed1fcb..dc22ba8 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -283,16 +283,14 @@ int ocfs2_set_acl(handle_t *handle,
int ocfs2_iop_set_acl(struct inode *inode, struct posix_acl *acl, int type)
{
struct buffer_head *bh = NULL;
- int status = 0;
+ int status, had_lock;
+ struct ocfs2_lock_holder oh;
- status = ocfs2_inode_lock(inode, &bh, 1);
- if (status < 0) {
- if (status != -ENOENT)
- mlog_errno(status);
- return status;
- }
+ had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);
+ if (had_lock < 0)
+ return had_lock;
status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);
- ocfs2_inode_unlock(inode, 1);
+ ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
brelse(bh);
return status;
}
@@ -302,21 +300,20 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
struct ocfs2_super *osb;
struct buffer_head *di_bh = NULL;
struct posix_acl *acl;
- int ret;
+ int had_lock;
+ struct ocfs2_lock_holder oh;
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);
- if (ret < 0) {
- if (ret != -ENOENT)
- mlog_errno(ret);
- return ERR_PTR(ret);
- }
+
+ had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 0, &oh);
+ if (had_lock < 0)
+ return ERR_PTR(had_lock);
acl = ocfs2_get_acl_nolock(inode, type, di_bh);
- ocfs2_inode_unlock(inode, 0);
+ ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);
brelse(di_bh);
return acl;
}
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 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
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 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
}
}
- 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 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
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 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
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_getattr(struct vfsmount *mnt,
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;
}
--
2.10.2
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