Date: Mon, 25 Nov 2013 21:10:44 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> Cc: Jan Mikkelsen <janm@transactionware.com>, freebsd-stable@FreeBSD.org Subject: Re: Help with filing a [maybe] ZFS/mmap bug. Message-ID: <5293A0B4.9070507@FreeBSD.org> In-Reply-To: <52939929.2090705@omnilan.de> 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> <52939929.2090705@omnilan.de>
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on 25/11/2013 20:38 Harald Schmalzbauer said the following:
> Bezüglich 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.c
>>>> 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 off, 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 clean.
>>>> + * 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 = rounddown2(off + nbytes, DEV_BSIZE);
>>>> + off = roundup2(off, DEV_BSIZE);
>>>> + nbytes = end - off;
>>>>
>>>> obj = 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, ==, VM_PAGE_BITS_ALL);
>>>> vm_object_pip_add(obj, 1);
>>>> pmap_remove_write(pp);
>>>> - vm_page_clear_dirty(pp, off, nbytes);
>>>> + if (nbytes != 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=255517&r2=258555
>
> But it uses rounddown2(), so I guess it's not workit atm, right?
Yeah, sorry about this.
I had a headsup and made a note to myself about it, but then got distracted at
the actual mfc time.
Should be fixed now.
--
Andriy Gapon
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