Date: Mon, 21 Aug 2006 08:37:38 -0500 From: Eric Anderson <anderson@centtech.com> To: Tor Egge <Tor.Egge@cvsup.no.freebsd.org> Cc: freebsd-fs@freebsd.org, tegge@freebsd.org Subject: Re: Deadlock between nfsd and snapshots. Message-ID: <44E9B722.2040407@centtech.com> In-Reply-To: <20060821.132151.41668008.Tor.Egge@cvsup.no.freebsd.org> References: <20060817170314.GA17490@peter.osted.lan> <20060818164903.GF20768@deviant.kiev.zoral.com.ua> <20060818.202001.74745664.Tor.Egge@cvsup.no.freebsd.org> <20060821.132151.41668008.Tor.Egge@cvsup.no.freebsd.org>
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On 08/21/06 08:21, Tor Egge wrote: > I wrote: > >> The deadlock indicates that one or more of IN_CHANGE, IN_MODIFIED or >> IN_UPDATE was set on the inode, indicating a write operation >> (e.g. VOP_WRITE(), VOP_RENAME(), VOP_CREATE(), VOP_REMOVE(), VOP_LINK(), >> VOP_SYMLINK(), VOP_SETATTR(), VOP_MKDIR(), VOP_RMDIR(), VOP_MKNOD()) that was >> not protected by vn_start_write() or vn_start_secondary_write(). > > The most common "write" operation was probably VOP_GETATTR(). > > ufs_itimes(), called from ufs_getattr(), might set the IN_MODIFIED inode flag > if IN_ACCESS is set on the inode even if neither IN_CHANGE nor IN_UPDATE is > set, transitioning the inode flags into a state where ufs_inactive() calls the > blocking variant of vn_start_secondary_write(). > > calling ufs_itimes() with only a shared vnode lock might cause unsafe accesses > to the inode flags. Setting of IN_ACCESS at the end of ffs_read() and > ffs_extread() might also be unsafe. If DIRECTIO is enabled then O_DIRECT reads > might not even attempt to set the IN_ACCESS flag. Does this mean that setting the noatime flag on mount would dodge this? Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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