Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764651AbXEVCcv (ORCPT ); Mon, 21 May 2007 22:32:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758963AbXEVCco (ORCPT ); Mon, 21 May 2007 22:32:44 -0400 Received: from sandeen.net ([209.173.210.139]:16037 "EHLO sandeen.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758803AbXEVCcn (ORCPT ); Mon, 21 May 2007 22:32:43 -0400 Message-ID: <46525648.8050807@sandeen.net> Date: Mon, 21 May 2007 21:32:40 -0500 From: Eric Sandeen User-Agent: Thunderbird 2.0.0.0 (Macintosh/20070326) MIME-Version: 1.0 To: Eric Sandeen CC: Andrew Morton , Linux Kernel Mailing List , Tejun Heo , Maneesh Soni , stable@kernel.org Subject: Re: [stable] [PATCH] - store sysfs inode nrs in s_ino to avoid readdir oopses References: <4651E0C9.3080609@redhat.com> <20070521153935.b549db8f.akpm@linux-foundation.org> <465236EF.40102@redhat.com> In-Reply-To: <465236EF.40102@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3867 Lines: 113 (2nd try, better(?) changelog, quilt refreshed(!) patch) -- Backport of ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/broken-out/gregkh-driver-sysfs-allocate-inode-number-using-ida.patch For regular files in sysfs, sysfs_readdir wants to traverse sysfs_dirent->s_dentry->d_inode->i_ino to get to the inode number. But, the dentry can be reclaimed under memory pressure, and there is no synchronization with readdir. This patch follows Tejun's scheme of allocating and storing an inode number in the new s_ino member of a sysfs_dirent, when dirents are created, and retrieving it from there for readdir, so that the pointer chain doesn't have to be traversed. Tejun's upstream patch uses a new-ish "ida" allocator which brings along some extra complexity; this -stable patch has a brain-dead incrementing counter which does not guarantee uniqueness, but because sysfs doesn't hash inodes as iunique expects, uniqueness wasn't guaranteed today anyway. Signed-off-by: Eric Sandeen Index: linux-2.6.21/fs/sysfs/dir.c =================================================================== --- linux-2.6.21.orig/fs/sysfs/dir.c +++ linux-2.6.21/fs/sysfs/dir.c @@ -30,6 +30,14 @@ static struct dentry_operations sysfs_de .d_iput = sysfs_d_iput, }; +static unsigned int sysfs_inode_counter; +ino_t sysfs_get_inum(void) +{ + if (unlikely(sysfs_inode_counter < 3)) + sysfs_inode_counter = 3; + return sysfs_inode_counter++; +} + /* * Allocates a new sysfs_dirent and links it to the parent sysfs_dirent */ @@ -41,6 +49,7 @@ static struct sysfs_dirent * __sysfs_new if (!sd) return NULL; + sd->s_ino = sysfs_get_inum(); atomic_set(&sd->s_count, 1); atomic_set(&sd->s_event, 1); INIT_LIST_HEAD(&sd->s_children); @@ -509,7 +518,7 @@ static int sysfs_readdir(struct file * f switch (i) { case 0: - ino = dentry->d_inode->i_ino; + ino = parent_sd->s_ino; if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0) break; filp->f_pos++; @@ -538,10 +547,7 @@ static int sysfs_readdir(struct file * f name = sysfs_get_name(next); len = strlen(name); - if (next->s_dentry) - ino = next->s_dentry->d_inode->i_ino; - else - ino = iunique(sysfs_sb, 2); + ino = next->s_ino; if (filldir(dirent, name, len, filp->f_pos, ino, dt_type(next)) < 0) Index: linux-2.6.21/fs/sysfs/inode.c =================================================================== --- linux-2.6.21.orig/fs/sysfs/inode.c +++ linux-2.6.21/fs/sysfs/inode.c @@ -140,6 +140,7 @@ struct inode * sysfs_new_inode(mode_t mo inode->i_mapping->a_ops = &sysfs_aops; inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info; inode->i_op = &sysfs_inode_operations; + inode->i_ino = sd->s_ino; lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key); if (sd->s_iattr) { Index: linux-2.6.21/fs/sysfs/mount.c =================================================================== --- linux-2.6.21.orig/fs/sysfs/mount.c +++ linux-2.6.21/fs/sysfs/mount.c @@ -33,6 +33,7 @@ static struct sysfs_dirent sysfs_root = .s_element = NULL, .s_type = SYSFS_ROOT, .s_iattr = NULL, + .s_ino = 1, }; static void sysfs_clear_inode(struct inode *inode) Index: linux-2.6.21/fs/sysfs/sysfs.h =================================================================== --- linux-2.6.21.orig/fs/sysfs/sysfs.h +++ linux-2.6.21/fs/sysfs/sysfs.h @@ -5,6 +5,7 @@ struct sysfs_dirent { void * s_element; int s_type; umode_t s_mode; + ino_t s_ino; struct dentry * s_dentry; struct iattr * s_iattr; atomic_t s_event; - 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/