Date: Mon, 21 Aug 2006 13:21:51 +0000 (UTC) From: Tor Egge <Tor.Egge@cvsup.no.freebsd.org> To: kostikbel@gmail.com Cc: freebsd-fs@freebsd.org, tegge@freebsd.org Subject: Re: Deadlock between nfsd and snapshots. Message-ID: <20060821.132151.41668008.Tor.Egge@cvsup.no.freebsd.org> In-Reply-To: <20060818.202001.74745664.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>
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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. - Tor Egge
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