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    SubjectRe: [PATCH 2/2] ocfs2: fix deadlocks when taking inode lock at vfs entry points
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    On 01/06/2017 03:14 PM, Joseph Qi wrote:
    >
    >
    > 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.
    Oh, sorry, I get your point this time. I think we need to check it if there are more than
    one processes that hold
    PR lock on the same resource. If I don't understand you correctly, please tell me why you
    think it's not neccessary
    to check before getting lock?

    Thanks,
    Eric
    >
    > Thanks,
    > Joseph
    >>
    >> Thanks for your review;-)
    >> Eric
    >>
    >>>
    >>> Thanks,
    >>> Joseph
    >>>>
    >>>> Signed-off-by: Eric Ren <zren@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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