Date: Mon, 8 Nov 2010 22:51:39 +0530 From: Aditya Sarawgi <sarawgi.aditya@gmail.com> To: Gleb Kurtsou <gleb.kurtsou@gmail.com> Cc: freebsd-fs@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: The state of Giant lock in the file systems? Message-ID: <20101108172136.GA2066@earth> In-Reply-To: <20101108143130.GA2799@tops> References: <ib8qda$nat$1@dough.gmane.org> <20101108143130.GA2799@tops>
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On Mon, Nov 08, 2010 at 04:31:30PM +0200, Gleb Kurtsou wrote: > On (08/11/2010 13:28), Ivan Voras wrote: > > I was looking at fusefs sources and there is a dance it does with the > > Giant lock which looks fishy. > It's intended to be fishy. No kernel level locks should be held before > returning to userland, in other words on each syscall vnode is locked (+ > Gaint lock for fs if needed), than it's unlocked by filesystem and > relocked upon callback from userspace. puffs is MPSAFE if that could be > of any help for you. > > > Grepping for "-ir giant" in /sys/fs on 8-stable shows only a handful of > > mentionings, but if I understand it correctly only these "active" instances: > > > > 1) one set of mtx_assert() calls on it in pseudofs, which I can't figure > > out what they're guarding > > 2) some manual locking and unlocking in nfsclient which appears to only > > guard printf() (???) > Somewhat unrelated, but. Does NFS client unlock vnodes while > sending/waiting for RCP reply? I thought it does, but I'm not sure. > > > 3) some more locking in nfsserver which apparently is only there to > > guard the underlying local file system > > 4) coda, which appears to be the only one marked with D_NEEDGIANT, but > > doesn't do much of its own interfacing with it > > > > Except for these, is there any more magic that would need to be resolved > > to excise Giant from VFS? > Kostik was working on it. > > > Would it be correct to think that coda is the single biggest obstacle? > Filesystem should be marked as MPSAFE, it's not D_NEEDGIANT flag but > MNTK_MPSAFE. A lot of filesystems are still locked by Gaint, i.e ext2fs, > smbfs, nwfs, ntfs, etc. > ext2fs on 9-CURRENT is MPSAFE. > > > > _______________________________________________ > > freebsd-fs@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
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