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Remove pthread rwlocks from vmd(8)'s qcow code.

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The users of this code are single threaded today. The locks also
don't look to fully protect key state in qcow images. If/when virtio
block emulation ends up with multiple virtqueues, this will need
to be revisited.

ok mlarkin@, hshoexer@
This commit is contained in:
dv
2026-03-28 16:22:04 +00:00
parent b39c1312a5
commit 2ec97aa487
1 changed files with 2 additions and 12 deletions
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14
usr.sbin/vmd/vioqcow2.c
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@@ -1,4 +1,4 @@
/* $OpenBSD: vioqcow2.c,v 1.26 2025/12/02 02:31:10 dv Exp $ */
/* $OpenBSD: vioqcow2.c,v 1.27 2026/03/28 16:22:04 dv Exp $ */
/*
* Copyright (c) 2018 Ori Bernstein <ori@eigenstate.org>
@@ -67,7 +67,6 @@ struct qcheader {
} __packed;
struct qcdisk {
pthread_rwlock_t lock;
struct qcdisk *base;
struct qcheader header;
@@ -214,7 +213,6 @@ qc2_open(struct qcdisk *disk, int *fds, size_t nfd)
off_t i;
int version, fd;
pthread_rwlock_init(&disk->lock, NULL);
fd = fds[0];
disk->fd = fd;
disk->base = NULL;
@@ -480,7 +478,6 @@ xlate(struct qcdisk *disk, off_t off, int *inplace)
*/
if (inplace)
*inplace = 0;
pthread_rwlock_rdlock(&disk->lock);
if (off < 0)
goto err;
@@ -491,10 +488,8 @@ xlate(struct qcdisk *disk, off_t off, int *inplace)
l2tab = disk->l1[l1off];
l2tab &= ~QCOW2_INPLACE;
if (l2tab == 0) {
pthread_rwlock_unlock(&disk->lock);
if (l2tab == 0)
return 0;
}
l2off = (off / disk->clustersz) % l2sz;
pread(disk->fd, &buf, sizeof(buf), l2tab + l2off * 8);
cluster = be64toh(buf);
@@ -506,14 +501,12 @@ xlate(struct qcdisk *disk, off_t off, int *inplace)
*inplace = !!(cluster & QCOW2_INPLACE);
if (cluster & QCOW2_COMPRESSED)
fatalx("%s: compressed clusters unsupported", __func__);
pthread_rwlock_unlock(&disk->lock);
clusteroff = 0;
cluster &= ~QCOW2_INPLACE;
if (cluster)
clusteroff = off % disk->clustersz;
return cluster + clusteroff;
err:
pthread_rwlock_unlock(&disk->lock);
return -1;
}
@@ -531,8 +524,6 @@ mkcluster(struct qcdisk *disk, struct qcdisk *base, off_t off, off_t src_phys)
off_t l2sz, l1off, l2tab, l2off, cluster, clusteroff, orig;
uint64_t buf;
pthread_rwlock_wrlock(&disk->lock);
cluster = -1;
/* L1 entries always exist */
l2sz = disk->clustersz / 8;
@@ -581,7 +572,6 @@ mkcluster(struct qcdisk *disk, struct qcdisk *base, off_t off, off_t src_phys)
fatalx("%s: could not write l1", __func__);
inc_refs(disk, cluster, 1);
pthread_rwlock_unlock(&disk->lock);
clusteroff = off % disk->clustersz;
if (cluster + clusteroff < disk->clustersz)
fatalx("write would clobber header");