Eric Ren
2017-Jan-16 03:06 UTC
[Ocfs2-devel] [PATCH 2/2] ocfs2: fix deadlocks when taking inode lock at vfs entry points
Hi Junxiao, On 01/16/2017 10:46 AM, Junxiao Bi wrote:>>> If had_lock==true, it is a bug? I think we should BUG_ON for it, that >>> can help us catch bug at the first time. >> Good idea! But I'm not sure if "ocfs2_setattr" is always the first one >> who takes the cluster lock. >> It's harder for me to name all the possible paths;-/ > The BUG_ON() can help catch the path where ocfs2_setattr is not the > first one.Yes, I understand. But, the problem is that the vfs entries calling order is out of our control. I don't want to place an assertion where I'm not 100% sure it's absolutely right;-) Thanks, Eric> > Thanks, > Junxiao. > >>> >>>> + 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); >>> The same thing as ocfs2_setattr. >> OK. I will think over your suggestions! >> >> Thanks, >> Eric >> >>> Thanks, >>> Junxiao. >>>> + 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; >>>> } >>>> >
Junxiao Bi
2017-Jan-16 03:13 UTC
[Ocfs2-devel] [PATCH 2/2] ocfs2: fix deadlocks when taking inode lock at vfs entry points
On 01/16/2017 11:06 AM, Eric Ren wrote:> Hi Junxiao, > > On 01/16/2017 10:46 AM, Junxiao Bi wrote: >>>> If had_lock==true, it is a bug? I think we should BUG_ON for it, that >>>> can help us catch bug at the first time. >>> Good idea! But I'm not sure if "ocfs2_setattr" is always the first one >>> who takes the cluster lock. >>> It's harder for me to name all the possible paths;-/ >> The BUG_ON() can help catch the path where ocfs2_setattr is not the >> first one. > Yes, I understand. But, the problem is that the vfs entries calling > order is out of our control. > I don't want to place an assertion where I'm not 100% sure it's > absolutely right;-)If it is not the first one, is it another recursive locking bug? In this case, if you don't like BUG_ON(), you can dump the call trace and print some warning message. Thanks, Junxiao.> > Thanks, > Eric > >> >> Thanks, >> Junxiao. >> >>>> >>>>> + 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); >>>> The same thing as ocfs2_setattr. >>> OK. I will think over your suggestions! >>> >>> Thanks, >>> Eric >>> >>>> Thanks, >>>> Junxiao. >>>>> + 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; >>>>> } >>>>> >> >