From: Gang He <ghe@suse.com> To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com Cc: Gang He <ghe@suse.com>, linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, akpm@linux-foundation.org Subject: [PATCH v2] ocfs2: ocfs2_downconvert_lock failure results in deadlock Date: Mon, 30 Aug 2021 12:46:21 +0800 [thread overview] Message-ID: <20210830044621.12544-1-ghe@suse.com> (raw) Usually, ocfs2_downconvert_lock() function always downconverts dlm lock to the expected level for satisfy dlm bast requests from the other nodes. But there is a rare situation. When dlm lock conversion is being canceled, ocfs2_downconvert_lock() function will return -EBUSY. You need to be aware that ocfs2_cancel_convert() function is asynchronous in fsdlm implementation. If we does not requeue this lockres entry, ocfs2 downconvert thread no longer handles this dlm lock bast request. Then, the other nodes will not get the dlm lock again, the current node's process will be blocked when acquire this dlm lock again. Signed-off-by: Gang He <ghe@suse.com> --- v2: keep error print in ocfs2_downconvert_lock function, add more detailed comments in code, add msleep to avoid repeated attempts. --- fs/ocfs2/dlmglue.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c index 48fd369c29a4..f8f561850470 100644 --- a/fs/ocfs2/dlmglue.c +++ b/fs/ocfs2/dlmglue.c @@ -16,6 +16,7 @@ #include <linux/debugfs.h> #include <linux/seq_file.h> #include <linux/time.h> +#include <linux/delay.h> #include <linux/quotaops.h> #include <linux/sched/signal.h> @@ -3912,6 +3913,17 @@ static int ocfs2_unblock_lock(struct ocfs2_super *osb, spin_unlock_irqrestore(&lockres->l_lock, flags); ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb, gen); + /* The dlm lock convert is being cancelled in background, + * ocfs2_cancel_convert() is asynchronous in fs/dlm, + * requeue it, try again later. + */ + if (ret == -EBUSY) { + ctl->requeue = 1; + mlog(ML_BASTS, "lockres %s, ReQ: Downconvert busy\n", + lockres->l_name); + ret = 0; + msleep(20); + } leave: if (ret) -- 2.12.3
WARNING: multiple messages have this Message-ID (diff)
From: Gang He <ghe@suse.com> To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com Subject: [Ocfs2-devel] [PATCH v2] ocfs2: ocfs2_downconvert_lock failure results in deadlock Date: Mon, 30 Aug 2021 12:46:21 +0800 [thread overview] Message-ID: <20210830044621.12544-1-ghe@suse.com> (raw) Usually, ocfs2_downconvert_lock() function always downconverts dlm lock to the expected level for satisfy dlm bast requests from the other nodes. But there is a rare situation. When dlm lock conversion is being canceled, ocfs2_downconvert_lock() function will return -EBUSY. You need to be aware that ocfs2_cancel_convert() function is asynchronous in fsdlm implementation. If we does not requeue this lockres entry, ocfs2 downconvert thread no longer handles this dlm lock bast request. Then, the other nodes will not get the dlm lock again, the current node's process will be blocked when acquire this dlm lock again. Signed-off-by: Gang He <ghe@suse.com> --- v2: keep error print in ocfs2_downconvert_lock function, add more detailed comments in code, add msleep to avoid repeated attempts. --- fs/ocfs2/dlmglue.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c index 48fd369c29a4..f8f561850470 100644 --- a/fs/ocfs2/dlmglue.c +++ b/fs/ocfs2/dlmglue.c @@ -16,6 +16,7 @@ #include <linux/debugfs.h> #include <linux/seq_file.h> #include <linux/time.h> +#include <linux/delay.h> #include <linux/quotaops.h> #include <linux/sched/signal.h> @@ -3912,6 +3913,17 @@ static int ocfs2_unblock_lock(struct ocfs2_super *osb, spin_unlock_irqrestore(&lockres->l_lock, flags); ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb, gen); + /* The dlm lock convert is being cancelled in background, + * ocfs2_cancel_convert() is asynchronous in fs/dlm, + * requeue it, try again later. + */ + if (ret == -EBUSY) { + ctl->requeue = 1; + mlog(ML_BASTS, "lockres %s, ReQ: Downconvert busy\n", + lockres->l_name); + ret = 0; + msleep(20); + } leave: if (ret) -- 2.12.3 _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel
next reply other threads:[~2021-08-30 4:46 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-30 4:46 Gang He [this message] 2021-08-30 4:46 ` [Ocfs2-devel] [PATCH v2] ocfs2: ocfs2_downconvert_lock failure results in deadlock Gang He 2021-08-30 11:05 ` Joseph Qi 2021-08-30 11:05 ` [Ocfs2-devel] " Joseph Qi
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