Date: Tue, 5 Aug 2008 11:32:29 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: freebsd-fs@freebsd.org Subject: Re: doing vfs_hash_get when vnode locked Message-ID: <20080805083229.GB97161@deviant.kiev.zoral.com.ua> In-Reply-To: <Pine.GSO.4.63.0808041657200.3482@muncher.cs.uoguelph.ca> References: <Pine.GSO.4.63.0808041657200.3482@muncher.cs.uoguelph.ca>
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--qnuS/wU1MXEWeKjo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 04, 2008 at 05:04:58PM -0400, Rick Macklem wrote: > There's a place in my nfsv4 client where I need to vfs_hash_get() when > another blocked thread may be holding a lock on the vnode. (It's during > a recovery case where the other threads are blocked, so there isn't a > race problem, as far as I understand it.) >=20 > For FreeBSD7, all I did was call vfs_hash_get() with flags =3D=3D 0 and it > gave me what I wanted (the vnode for the file handle with a reference > count, but no lock). >=20 > For FreeBSD-CURRENT/8, this no longer works, because vfs_hash_get() calls > vget(), which calls _vn_lock() and _vn_lock() now complains if the lock > type field of "flags" is 0. I came up with a really ugly workaround, by > setting the flags arg. to LK_EXCLOTHER for vfs_hash_get() and then > providing my own VOP_LOCK1() which just VI_UNLOCK()s and returns 0 for > this case (doing the same as vop_stdlock() for other cases). Yuck!! >=20 > Is it possible to re-enable the case of _vn_lock() getting a locktype > field =3D=3D 0 (or defining one that says "just return 0 unless VI_DOOMED= "), > so I don't need the dirty hack? I do not quite understand what you really need there. The non-locked vnode may be reclaimed at any moment, so the check for !VI_DOOMED returns no useful information. --qnuS/wU1MXEWeKjo Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkiYEB0ACgkQC3+MBN1Mb4gt+gCfSgADScqDKFM/6MZ+P3odCjXZ l6QAoL9x78alOWSpFGCzB+CT70FB2JAM =x5zz -----END PGP SIGNATURE----- --qnuS/wU1MXEWeKjo--
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