Hi Guozhonghua,
The case you described can not happen.
slot is protected by super lock, which has already refreshed slot info.
Thanks,
Joseph
On 2015/12/25 11:14, Guozhonghua wrote:
> Hi Jiang,
>
>
>
> I think there is another scenario about slot overwritten issue.
>
> There are three nodes in the ocfs2 cluster. Node 3 had mounted with slot 1.
>
> Node 1 and node 2 execute mounting volume operation at the same time.
>
>
>
> N1 N2
>
> mount ocfs2 volume mount ocfs2 volume
>
> ocfs2_fill_super() ocfs2_fill_super()
>
> ocfs2_initialize_super ocfs2_initialize_super
>
> ... ... ... ...
>
> ocfs2_init_slot_info(osb); ocfs2_init_slot_info(osb);
>
> ocfs2_mount_volume ocfs2_mount_volume
>
> ocfs2_super_lock ocfs2_super_lock
>
> Gotten the super lock Waiting for the super lock
>
> Find slot 0 unused
>
> from memory
>
> update the slot 0 with 1
>
> ... ...
>
> locked journal 0
>
> mount finished.
>
> Gotten super lock and
>
>
> Also find slot 0 unused
>
>
> from memory,
>
>
> update the slot 0 with node num 2
>
>
> But Journal 0 is locked by N1
>
>
> Mounted hang up.
>
> ... ... ... ...
>
> umount volume ... ...
>
> cleare the slot 0 ... ...
>
> Gotten joural 0 lock
>
> mount finished.
>
> But
> here, the slot 0 is cleare by N1
>
>
>
> IF N1 mount again
>
> Same condition with N2
>
> and will hang up.
>
>
>
> In the function of ocfs2_mount_volume, I think the slot info should be
> refreshed after ocfs2_super_lock called.
>
> static int ocfs2_mount_volume(struct super_block *sb)
>
> {
>
> status = ocfs2_super_lock(osb, 1);
>
> ......
>
>
>
> + status = ocfs2_refresh_slot_info(osb);
>
> + if (status < 0) {
>
> + mlog_errno(status);
>
> + goto leave;
>
> + }
>
> ... ...
>
> }
>
>
>
> Another way is to move ocfs2_init_slot_info() function from
> ocfs2_initialize_super to replace ocfs2_refresh_slot_info as above.
>
>
>
>
>
> Message: 5
>
> Date: Wed, 23 Dec 2015 18:23:36 +0800
>
> From: jiangyiwen <jiangyi...@huawei.com <mailto:jiangyi...@huawei.com>>
>
> Subject: [Ocfs2-devel] [PATCH] ocfs2: fix slot overwritten if storage
>
> link down during mount
>
> To: Andrew Morton <a...@linux-foundation.org
> <mailto:a...@linux-foundation.org>>
>
> Cc: Mark Fasheh <mfas...@suse.de <mailto:mfas...@suse.de>>,
> ocfs2-devel@oss.oracle.com <mailto:ocfs2-devel@oss.oracle.com>
>
> Message-ID: <567a7628.5040...@huawei.com <mailto:567a7628.5040...@huawei.com>>
>
> Content-Type: text/plain; charset="utf-8"
>
>
>
> The following case will lead to slot overwritten.
>
>
>
> N1 N2
>
> mount ocfs2 volume, find and
>
> allocate slot 0, then set
>
> osb->slot_num to 0, begin to
>
> write slot info to disk
>
> mount ocfs2 volume, wait for super lock
>
> write block fail because of
>
> storage link down, unlock
>
> super lock
>
> got super lock and also allocate slot 0
>
> then unlock super lock
>
>
>
> mount fail and then dismount,
>
> since osb->slot_num is 0, try to
>
> put invalid slot to disk. And it
>
> will succeed if storage link
>
> restores.
>
> N2 slot info is now overwritten
>
>
>
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