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Do not cluster with B_LOCKED buffers.

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This is an odd one.  This patch appears to fix a panic related to background
bitmap writes (for FFS), though neither Kirk, Ian, or I can figure out how
B_CLUSTEROK could possibly be set on a bitmap block to cause the clustering
code to improperly cluster with a buffer undergoing a background write.

In anycase, the clustering code is very fragile and this patch helps with
that, as well as possibly fixing a bug Andre was having.

Suggested by: Ian Dowse <iedowse@maths.tcd.ie>
Testing by: Andre Albsmeier <andre.albsmeier@mchp.siemens.de>
This commit is contained in:
Matthew Dillon 2001-01-19 05:31:07 +00:00
parent 08812b3925
commit bcc740c453
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=71230
1 changed files with 20 additions and 4 deletions
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24
sys/kern/vfs_cluster.c
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@ -399,15 +399,22 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
tbp = getblk(vp, lbn + i, size, 0, 0);
if ((tbp->b_flags & B_CACHE) ||
/*
* If the buffer is already fully valid or locked
* (which could also mean that a background write is
* in progress), or the buffer is not backed by VMIO,
* stop.
*/
if ((tbp->b_flags & (B_CACHE|B_LOCKED)) ||
(tbp->b_flags & B_VMIO) == 0) {
bqrelse(tbp);
break;
}
for (j = 0;j < tbp->b_npages; j++)
for (j = 0;j < tbp->b_npages; j++) {
if (tbp->b_pages[j]->valid)
break;
}
if (j != tbp->b_npages) {
bqrelse(tbp);
@ -710,8 +717,13 @@ cluster_wbuild(vp, size, start_lbn, len)
while (len > 0) {
s = splbio();
/*
* If the buffer is not delayed-write (i.e. dirty), or it
* is delayed-write but either locked or inval, it cannot
* partake in teh clustered write.
*/
if (((tbp = gbincore(vp, start_lbn)) == NULL) ||
((tbp->b_flags & (B_INVAL | B_DELWRI)) != B_DELWRI) ||
((tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) != B_DELWRI) ||
BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) {
++start_lbn;
--len;
@ -784,12 +796,16 @@ cluster_wbuild(vp, size, start_lbn, len)
/*
* If it IS in core, but has different
* characteristics, don't cluster with it.
* characteristics, or is locked (which
* means it could be undergoing a background
* I/O or be in a weird state), then don't
* cluster with it.
*/
if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
B_INVAL | B_DELWRI | B_NEEDCOMMIT))
!= (B_DELWRI | B_CLUSTEROK |
(bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
(tbp->b_flags & B_LOCKED) ||
tbp->b_wcred != bp->b_wcred ||
BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT)) {
splx(s);