From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:52570 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbcL1Mgv (ORCPT ); Wed, 28 Dec 2016 07:36:51 -0500 From: Coly Li To: linux-fsdevel@vger.kernel.org Cc: nongli1031@gmail.com, Coly Li , Andrew Morton , Richard Weinberger , linux-mtd@lists.infradead.org Subject: [PATCH v3] romfs: use different way to generate fsid for BLOCK or MTD Date: Wed, 28 Dec 2016 20:36:36 +0800 Message-Id: <1482928596-115155-1-git-send-email-colyli@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 'Commit 8a59f5d25265 ("fs/romfs: return f_fsid for statfs(2)")' generates a 64bit id from sb->s_bdev->bd_dev. This is only correct when romfs is defined with CONFIG_ROMFS_ON_BLOCK. If romfs is only defined with CONFIG_ROMFS_ON_MTD, sb->s_bdev is NULL, referencing sb->s_bdev->bd_dev will triger an oops. Richard Weinberger points out that when CONFIG_ROMFS_BACKED_BY_BOTH=y, both CONFIG_ROMFS_ON_BLOCK and CONFIG_ROMFS_ON_MTD are defined. Therefore when calling huge_encode_dev() to generate a 64bit id, I use the follow order to choose parameter, - CONFIG_ROMFS_ON_BLOCK defined use sb->s_bdev->bd_dev - CONFIG_ROMFS_ON_BLOCK undefined and CONFIG_ROMFS_ON_MTD defined use sb->s_dev when, - both CONFIG_ROMFS_ON_BLOCK and CONFIG_ROMFS_ON_MTD undefined leave id as 0 When CONFIG_ROMFS_ON_MTD is defined and sb->s_mtd is not NULL, sb->s_dev is set to a device ID generated by MTD_BLOCK_MAJOR and mtd index, otherwise sb->s_dev is 0. This is a try-best effort to generate a uniq file system ID, if all the above conditions are not meet, f_fsid of this romfs instance will be 0. Generally only one romfs can be built on single MTD block device, this method is enough to identify multiple romfs instances in a computer. Signed-off-by: Coly Li Reported-by: Nong Li Tested-by: Nong Li Cc: Andrew Morton Cc: Richard Weinberger Cc: linux-fsdevel@vger.kernel.org Cc: linux-mtd@lists.infradead.org --- fs/romfs/super.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/fs/romfs/super.c b/fs/romfs/super.c index d0f8a38..0186fe6 100644 --- a/fs/romfs/super.c +++ b/fs/romfs/super.c @@ -74,6 +74,7 @@ #include #include #include +#include #include "internal.h" static struct kmem_cache *romfs_inode_cachep; @@ -416,7 +417,22 @@ static void romfs_destroy_inode(struct inode *inode) static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) { struct super_block *sb = dentry->d_sb; - u64 id = huge_encode_dev(sb->s_bdev->bd_dev); + u64 id = 0; + + /* When calling huge_encode_dev(), + * use sb->s_bdev->bd_dev when, + * - CONFIG_ROMFS_ON_BLOCK defined + * use sb->s_dev when, + * - CONFIG_ROMFS_ON_BLOCK undefined and + * - CONFIG_ROMFS_ON_MTD defined + * leave id as 0 when, + * - CONFIG_ROMFS_ON_BLOCK undefined and + * - CONFIG_ROMFS_ON_MTD undefined + */ + if (sb->s_bdev) + id = huge_encode_dev(sb->s_bdev->bd_dev); + else if (sb->s_dev) + id = huge_encode_dev(sb->s_dev); buf->f_type = ROMFS_MAGIC; buf->f_namelen = ROMFS_MAXFN; @@ -489,6 +505,11 @@ static int romfs_fill_super(struct super_block *sb, void *data, int silent) sb->s_flags |= MS_RDONLY | MS_NOATIME; sb->s_op = &romfs_super_ops; +#ifdef CONFIG_ROMFS_ON_MTD + /* Use same dev ID from the underlying mtdblock device */ + if (sb->s_mtd) + sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); +#endif /* read the image superblock and check it */ rsb = kmalloc(512, GFP_KERNEL); if (!rsb) -- 2.6.6