[Ocfs2-devel] [PATCH 2/2] ocfs2: fix deadlocks when taking inode lock at vfs entry points
Joseph Qi
jiangqi903 at gmail.com
Thu Jan 5 23:14:38 PST 2017
On 17/1/6 14:56, Eric Ren wrote:
> 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
I mean we have no need to check if locked by me, just do inode lock and
add holder.
This will make code more clean, IMO.
Thanks,
Joseph
>
> Thanks for your review;-)
> Eric
>
>>
>> Thanks,
>> Joseph
>>>
>>> Signed-off-by: Eric Ren <zren at 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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