Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932735AbVKDM5M (ORCPT ); Fri, 4 Nov 2005 07:57:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932734AbVKDM5M (ORCPT ); Fri, 4 Nov 2005 07:57:12 -0500 Received: from mtagate4.de.ibm.com ([195.212.29.153]:41098 "EHLO mtagate4.de.ibm.com") by vger.kernel.org with ESMTP id S932735AbVKDM5K (ORCPT ); Fri, 4 Nov 2005 07:57:10 -0500 Date: Fri, 4 Nov 2005 13:57:05 +0100 From: Heiko Carstens To: Al Viro Cc: Andrew Morton , linux-kernel@vger.kernel.org, Andreas Herrmann Subject: Re: [PATCH resubmit] do_mount: reduce stack consumption Message-ID: <20051104125705.GB12476@osiris.boeblingen.de.ibm.com> References: <20051104105026.GA12476@osiris.boeblingen.de.ibm.com> <20051104114818.GG7992@ftp.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051104114818.GG7992@ftp.linux.org.uk> User-Agent: mutt-ng/devel (Linux) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5951 Lines: 211 > > This is a resubmit of Andreas' patch that reduces stackframe usage in > > do_mount. Problem is that without this patch we get a kernel stack > > overflow if we run with 4k stacks (s390 31 bit mode). > > See original stack back trace below and Andreas' patch and analysis > > here: > > http://www.ussg.iu.edu/hypermail/linux/kernel/0410.3/1844.html > > NAK. Rationale: too ugly. Ok, since I can only guess what you don't like: here is an updated patch that probably addresses a few things. If you don't like this one too, could you please explain what should be changed? Thanks, Heiko --- fs/namespace.c | 79 ++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 50 insertions(+), 29 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 2fa9fdf..c14fbfc 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -619,25 +619,30 @@ out_unlock: */ static int do_loopback(struct nameidata *nd, char *old_name, int recurse) { - struct nameidata old_nd; + struct nameidata *old_nd; struct vfsmount *mnt = NULL; int err = mount_is_safe(nd); if (err) return err; if (!old_name || !*old_name) return -EINVAL; - err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); + + old_nd = kmalloc(sizeof(*old_nd), GFP_KERNEL); + if (!old_nd) + return -ENOMEM; + + err = path_lookup(old_name, LOOKUP_FOLLOW, old_nd); if (err) - return err; + goto out; down_write(¤t->namespace->sem); err = -EINVAL; - if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd.mnt))) { + if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd->mnt))) { err = -ENOMEM; if (recurse) - mnt = copy_tree(old_nd.mnt, old_nd.dentry); + mnt = copy_tree(old_nd->mnt, old_nd->dentry); else - mnt = clone_mnt(old_nd.mnt, old_nd.dentry); + mnt = clone_mnt(old_nd->mnt, old_nd->dentry); } if (mnt) { @@ -656,7 +661,9 @@ static int do_loopback(struct nameidata } up_write(¤t->namespace->sem); - path_release(&old_nd); + path_release(old_nd); +out: + kfree(old_nd); return err; } @@ -693,22 +700,28 @@ static int do_remount(struct nameidata * static int do_move_mount(struct nameidata *nd, char *old_name) { - struct nameidata old_nd, parent_nd; + struct { + struct nameidata old_nd, parent_nd; + } *loc; struct vfsmount *p; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!old_name || !*old_name) return -EINVAL; - err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); + loc = kmalloc(sizeof(*loc), GFP_KERNEL); + if (!loc) + return -ENOMEM; + + err = path_lookup(old_name, LOOKUP_FOLLOW, &loc->old_nd); if (err) - return err; + goto path_out; down_write(¤t->namespace->sem); while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) ; err = -EINVAL; - if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) + if (!check_mnt(nd->mnt) || !check_mnt(loc->old_nd.mnt)) goto out; err = -ENOENT; @@ -721,28 +734,28 @@ static int do_move_mount(struct nameidat goto out2; err = -EINVAL; - if (old_nd.dentry != old_nd.mnt->mnt_root) + if (loc->old_nd.dentry != loc->old_nd.mnt->mnt_root) goto out2; - if (old_nd.mnt == old_nd.mnt->mnt_parent) + if (loc->old_nd.mnt == loc->old_nd.mnt->mnt_parent) goto out2; if (S_ISDIR(nd->dentry->d_inode->i_mode) != - S_ISDIR(old_nd.dentry->d_inode->i_mode)) + S_ISDIR(loc->old_nd.dentry->d_inode->i_mode)) goto out2; err = -ELOOP; for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent) - if (p == old_nd.mnt) + if (p == loc->old_nd.mnt) goto out2; err = 0; - detach_mnt(old_nd.mnt, &parent_nd); - attach_mnt(old_nd.mnt, nd); + detach_mnt(loc->old_nd.mnt, &loc->parent_nd); + attach_mnt(loc->old_nd.mnt, nd); /* if the mount is moved, it should no longer be expire * automatically */ - list_del_init(&old_nd.mnt->mnt_expire); + list_del_init(&loc->old_nd.mnt->mnt_expire); out2: spin_unlock(&vfsmount_lock); out1: @@ -750,8 +763,10 @@ out1: out: up_write(¤t->namespace->sem); if (!err) - path_release(&parent_nd); - path_release(&old_nd); + path_release(&loc->parent_nd); + path_release(&loc->old_nd); +path_out: + kfree(loc); return err; } @@ -1014,7 +1029,7 @@ int copy_mount_options(const void __user long do_mount(char * dev_name, char * dir_name, char *type_page, unsigned long flags, void *data_page) { - struct nameidata nd; + struct nameidata *nd; int retval = 0; int mnt_flags = 0; @@ -1041,27 +1056,33 @@ long do_mount(char * dev_name, char * di mnt_flags |= MNT_NOEXEC; flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_ACTIVE); + nd = kmalloc(sizeof(*nd), GFP_KERNEL); + if (!nd) + return -ENOMEM; + /* ... and get the mountpoint */ - retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); + retval = path_lookup(dir_name, LOOKUP_FOLLOW, nd); if (retval) - return retval; + goto path_out; - retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); + retval = security_sb_mount(dev_name, nd, type_page, flags, data_page); if (retval) goto dput_out; if (flags & MS_REMOUNT) - retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, + retval = do_remount(nd, flags & ~MS_REMOUNT, mnt_flags, data_page); else if (flags & MS_BIND) - retval = do_loopback(&nd, dev_name, flags & MS_REC); + retval = do_loopback(nd, dev_name, flags & MS_REC); else if (flags & MS_MOVE) - retval = do_move_mount(&nd, dev_name); + retval = do_move_mount(nd, dev_name); else - retval = do_new_mount(&nd, type_page, flags, mnt_flags, + retval = do_new_mount(nd, type_page, flags, mnt_flags, dev_name, data_page); dput_out: - path_release(&nd); + path_release(nd); +path_out: + kfree(nd); return retval; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/