Date: Wed, 4 Dec 2013 18:20:29 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Paolo Pinto <paolo.pinto@netasq.com> Cc: nicolas dumont <nicolas.dumont@netasq.com>, freebsd-geom@freebsd.org Subject: Re: geom_uzip, panic: bio_length in mdstart_vnode() Message-ID: <20131204162029.GV59496@kib.kiev.ua> In-Reply-To: <529F2748.2060900@netasq.com> References: <529F2748.2060900@netasq.com>
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On Wed, Dec 04, 2013 at 01:59:52PM +0100, Paolo Pinto wrote:
> Hi list!
>
> My kernel is compiled with option INVARIANTS and I get a reproducible
> kernel panic when trying to read data from a GEOM based compressed
> memory disk:
>
> Unread portion of the kernel message buffer:
> panic: bio_length 140288
> cpuid = 3
> KDB: stack backtrace:
> #0 0xffffffff80909726 at kdb_backtrace+0x66
> #1 0xffffffff808d0fa8 at panic+0x1d8
> #2 0xffffffff80595949 at mdstart_vnode+0x619
The issue is that geom_uzip creates bios which are larger than MAXPHYS.
As a workaround, the following patch should be enough. It only fires
assert when md really uses pbuf, and since geom_uzip knows nothing
about unmapped bio, the assertion must not trigger.
diff --git a/sys/dev/md/md.c b/sys/dev/md/md.c
index 8ae51d1..639677e 100644
--- a/sys/dev/md/md.c
+++ b/sys/dev/md/md.c
@@ -746,12 +746,12 @@ mdstart_vnode(struct md_s *sc, struct bio *bp)
return (error);
}
- KASSERT(bp->bio_length <= MAXPHYS, ("bio_length %jd",
- (uintmax_t)bp->bio_length));
if ((bp->bio_flags & BIO_UNMAPPED) == 0) {
pb = NULL;
aiov.iov_base = bp->bio_data;
} else {
+ KASSERT(bp->bio_length <= MAXPHYS, ("bio_length %jd",
+ (uintmax_t)bp->bio_length));
pb = getpbuf(&md_vnode_pbuf_freecnt);
pmap_qenter((vm_offset_t)pb->b_data, bp->bio_ma, bp->bio_ma_n);
aiov.iov_base = (void *)((vm_offset_t)pb->b_data +
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