From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from server.coly.li ([162.144.45.48]:39330 "EHLO server.coly.li" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750714AbdAWPem (ORCPT ); Mon, 23 Jan 2017 10:34:42 -0500 Subject: Re: [PATCH v3] romfs: use different way to generate fsid for BLOCK or MTD To: Coly Li , linux-fsdevel@vger.kernel.org, Andrew Morton References: <1482928596-115155-1-git-send-email-colyli@suse.de> Cc: nongli1031@gmail.com, Richard Weinberger , linux-mtd@lists.infradead.org From: Coly Li Message-ID: <09fe6908-348c-8f8b-c201-6e5d596b910f@coly.li> Date: Mon, 23 Jan 2017 22:52:09 +0800 MIME-Version: 1.0 In-Reply-To: <1482928596-115155-1-git-send-email-colyli@suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hi Andrew, This fix is verified by Nong Li, it works well in all three conditions, - CONFIG_ROMFS_ON_BLOCK defined - CONFIG_ROMFS_ON_BLOCK undefined and CONFIG_ROMFS_ON_MTD defined - both CONFIG_ROMFS_ON_BLOCK and CONFIG_ROMFS_ON_MTD undefined Last time the original patch was picked by you, could you please take care it again this time. Thanks in advance. Coly Li On 2016/12/28 下午8:36, Coly Li wrote: > '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) > -- Coly Li