Attachment 153037 Details for Bug 237126 – patch posted to rhkernel on 04/19

patch posted to rhkernel on 04/19

dlm-lkid-format.patch (text/plain), 2.00 KB, created by David Teigland on 2007-04-19 17:36:50 UTC

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Creator: David Teigland

Created: 2007-04-19 17:36:50 UTC

Size: 2.00 KB

patch

obsolete

>[PATCH] dlm: change lkid format
>
>bz 237126
>
>A lock id is a uint32 and is used as an opaque reference to the lock.  For
>userland apps, the lkid is passed up, through libdlm, as the return value
>from a write() on the dlm device.  This created a problem when the high
>bit was 1, making the lkid look like an error.  This is fixed by changing
>how the lkid is composed.  The low 16 bits identified the hash bucket for
>the lock and the high 16 bits were a per-bucket counter (which eventually
>hit 0x8000 causing the problem).  These are simply swapped around; the
>number of hash table buckets is far below 0x8000, making all lkid's
>positive when viewed as signed.
>
>Index: linux-2.6.21-rc5-quilt/fs/dlm/lock.c
>===================================================================
>--- linux-2.6.21-rc5-quilt.orig/fs/dlm/lock.c	2007-04-02 11:01:12.000000000 -0500
>+++ linux-2.6.21-rc5-quilt/fs/dlm/lock.c	2007-04-02 11:10:32.000000000 -0500
>@@ -580,7 +580,7 @@
> 	/* counter can roll over so we must verify lkid is not in use */
> 
> 	while (lkid == 0) {
>-		lkid = bucket | (ls->ls_lkbtbl[bucket].counter++ << 16);
>+		lkid = (bucket << 16) | ls->ls_lkbtbl[bucket].counter++;
> 
> 		list_for_each_entry(tmp, &ls->ls_lkbtbl[bucket].list,
> 				    lkb_idtbl_list) {
>@@ -601,8 +601,8 @@
> 
> static struct dlm_lkb *__find_lkb(struct dlm_ls *ls, uint32_t lkid)
> {
>-	uint16_t bucket = lkid & 0xFFFF;
> 	struct dlm_lkb *lkb;
>+	uint16_t bucket = (lkid >> 16);
> 
> 	list_for_each_entry(lkb, &ls->ls_lkbtbl[bucket].list, lkb_idtbl_list) {
> 		if (lkb->lkb_id == lkid)
>@@ -614,7 +614,7 @@
> static int find_lkb(struct dlm_ls *ls, uint32_t lkid, struct dlm_lkb **lkb_ret)
> {
> 	struct dlm_lkb *lkb;
>-	uint16_t bucket = lkid & 0xFFFF;
>+	uint16_t bucket = (lkid >> 16);
> 
> 	if (bucket >= ls->ls_lkbtbl_size)
> 		return -EBADSLT;
>@@ -644,7 +644,7 @@
> 
> static int __put_lkb(struct dlm_ls *ls, struct dlm_lkb *lkb)
> {
>-	uint16_t bucket = lkb->lkb_id & 0xFFFF;
>+	uint16_t bucket = (lkb->lkb_id >> 16);
> 
> 	write_lock(&ls->ls_lkbtbl[bucket].lock);
> 	if (kref_put(&lkb->lkb_ref, kill_lkb)) {

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Attachments on bug 237126: 153037