Date: Fri, 21 Mar 2008 14:50:42 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Jeff Roberson <jroberson@chesapeake.net> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/ufs/ffs ffs_vnops.c Message-ID: <20080321125042.GU10374@deviant.kiev.zoral.com.ua> In-Reply-To: <20080321024123.P910@desktop> References: <200803211233.m2LCX1Bm099652@repoman.freebsd.org> <20080321024123.P910@desktop>
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--XQjj8pZWZgZH7jIp Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 21, 2008 at 02:44:39AM -1000, Jeff Roberson wrote: > On Fri, 21 Mar 2008, Konstantin Belousov wrote: >=20 > >kib 2008-03-21 12:33:00 UTC > > > > FreeBSD src repository > > > > Modified files: > > sys/ufs/ffs ffs_vnops.c > > Log: > > Reduce the acquisition of the vnode interlock in the ffs_read() and > > ffs_extread() when setting the IN_ACCESS flag by checking whether the > > IN_ACCESS is already set. The possible race there is admissible. >=20 > I don't believe there is a race because we should always hold an exclusiv= e=20 > vnode lock and the vnode interlock when clearing. The exclusive node loc= k=20 We may hold only the shared vnode lock and the interlock when clearing, in the ufs_itimes(). > would prevent ffs_read() from executing entirely, so we don't have to=20 > worry about races with clearing the bit. Races to set the bit are handle= d=20 > by the vnode interlock. Yes, the race I meant is the clearing of the IN_ACCESS while performing unlocked read for check. It may be considered as a race, may be not. >=20 > I should also mention that while this may seem innocuous enough this=20 > figured heavily in LOCK_PROFILING for a real workload. >=20 > Thanks, > Jeff >=20 > > > > Tested by: pho > > Submitted by: jeff > > > > Revision Changes Path > > 1.180 +4 -2 src/sys/ufs/ffs/ffs_vnops.c > > --XQjj8pZWZgZH7jIp Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) iEYEARECAAYFAkfjryEACgkQC3+MBN1Mb4g30gCdGd/A6EpvJbh7AkRTO2CTwO9A RpYAoPdV5Rylxa89yArpBdTxgilOlUop =dhol -----END PGP SIGNATURE----- --XQjj8pZWZgZH7jIp--
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