Date: Mon, 25 Nov 2013 19:38:33 +0100 From: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> To: Andriy Gapon <avg@freebsd.org> Cc: Jan Mikkelsen <janm@transactionware.com>, freebsd-stable@freebsd.org Subject: Re: Help with filing a [maybe] ZFS/mmap bug. Message-ID: <52939929.2090705@omnilan.de> In-Reply-To: <5289DFFD.7080607@FreeBSD.org> References: <20967.760.95825.310085@gargle.gargle.HOWL><51E80B30.1090004@FreeBSD.org><20968.10645.880772.30501@gargle.gargle.HOWL><520202E5.30300@FreeBSD.org><20994.55913.93606.436124@gargle.gargle.HOWL><FEE7BDCF7F494EE1BA0BE9424275AA91@multiplay.co.uk> <21111.12085.958991.356982@gargle.gargle.HOWL> <4EB902F80CE84DD2BF36C85EF4CE8EF8@multiplay.co.uk> <5284B8A5.8040604@FreeBSD.org> <52889105.7040404@FreeBSD.org> <4B5798F5-269A-4E71-9799-E1B4E0C1545F@transactionware.com> <5289DFFD.7080607@FreeBSD.org>
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Bez=FCglich Andriy Gapon's Nachricht vom 18.11.2013 10:38 (localtime):
> ...
>>> Here is a patch (for head) that should fix the described above issue:=
>>>
>>> diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops=
=2Ec
>>> b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
>>> index 2e2cbd6..4fcd571 100644
>>> --- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
>>> +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
>>> @@ -328,6 +328,20 @@ page_busy(vnode_t *vp, int64_t start, int64_t of=
f, int64_t
>>> nbytes)
>>> {
>>> vm_object_t obj;
>>> vm_page_t pp;
>>> + int64_t end;
>>> +
>>> + /*
>>> + * At present vm_page_clear_dirty extends the cleared range to DEV_=
BSIZE
>>> + * aligned boundaries, if the range is not aligned. As a result a
>>> + * DEV_BSIZE subrange with partially dirty data may get marked as c=
lean.
>>> + * It may happen that all DEV_BSIZE subranges are marked clean and =
thus
>>> + * the whole page would be considred clean despite have some dirty =
data.
>>> + * For this reason we should shrink the range to DEV_BSIZE aligned
>>> + * boundaries before calling vm_page_clear_dirty.
>>> + */
>>> + end =3D rounddown2(off + nbytes, DEV_BSIZE);
>>> + off =3D roundup2(off, DEV_BSIZE);
>>> + nbytes =3D end - off;
>>>
>>> obj =3D vp->v_object;
>>> zfs_vmobject_assert_wlocked(obj);
>>> @@ -362,7 +376,8 @@ page_busy(vnode_t *vp, int64_t start, int64_t off=
, int64_t
>>> nbytes)
>>> ASSERT3U(pp->valid, =3D=3D, VM_PAGE_BITS_ALL);
>>> vm_object_pip_add(obj, 1);
>>> pmap_remove_write(pp);
>>> - vm_page_clear_dirty(pp, off, nbytes);
>>> + if (nbytes !=3D 0)
>>> + vm_page_clear_dirty(pp, off, nbytes);
>>> }
>>> break;
>>> }
>>
>> 9.2 does not seem to have a rounddown2() macro.
> Thanks for the heads-up!
> You could use a plain rounddown() or just 'x & ~(DEV_BSIZE - 1)'.
Hello,
saw that this fix made it int 9-stable:
http://svnweb.freebsd.org/base/stable/9/sys/cddl/contrib/opensolaris/uts/=
common/fs/zfs/zfs_vnops.c?r1=3D255517&r2=3D258555
But it uses rounddown2(), so I guess it's not workit atm, right?
Thanks,
-Harry
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