NetBSD Problem Report #45676
From yamt@NetBSD.org Fri Dec 2 12:13:28 2011
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Date: Fri, 2 Dec 2011 12:13:28 +0000 (UTC)
From: yamt@NetBSD.org
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To: gnats-bugs@NetBSD.org
Subject: ffs/wapbl problems
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>Number: 45676
>Category: kern
>Synopsis: ffs/wapbl problems
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: jdolecek
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Fri Dec 02 12:15:00 +0000 2011
>Last-Modified: Wed Apr 05 18:42:50 +0000 2017
>Originator: YAMAMOTO Takashi
>Release: NetBSD current
>Organization:
>Environment:
>Description:
1. ffs_full_fsync has code to skip wapbl_flush if vp->v_dirtyblkhd is
empty. i don't think it's a safe optimization because the buffer
which contains dinode would hang on devvp, not this vp. probably
another per-vnode/inode field is necessary to remember if the log is
involved for the file.
2. ffs_full_fsync and ffs_fsync skip wapbl_flush for FSYNC_DATAONLY.
it seems wrong because block pointers should be written out.
3. ffs_full_fsync and ffs_fsync does not obey FSYNC_CACHE when wapbl
is used but wapbl_flush is not necessary.
4. ffs_full_fsync and ffs_fsync should be merged as now softdep has
gone.
5. wapbl_flush issues two DIOCCACHESYNC calls which are typically
very expensive. while i'm not sure why _only_ this part of code
needs this level of guarantee, at least it should be reduced to
a single call, probably using a checksum as the comment in
wapbl_write_commit suggests.
6. wapbl should have underlying device requirements documented
somewhere. (torn writes, disk cache behaviour, etc)
>How-To-Repeat:
code inspection.
>Fix:
>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: kern-bug-people->jdolecek
Responsible-Changed-By: jdolecek@NetBSD.org
Responsible-Changed-When: Wed, 05 Apr 2017 18:42:50 +0000
Responsible-Changed-Why:
Collecting WAPBL reports.
>Unformatted:
(Contact us)
$NetBSD: query-full-pr,v 1.39 2013/11/01 18:47:49 spz Exp $
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