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authorColy Li <colyli@suse.de>2017-01-24 15:18:46 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-06-17 06:39:38 +0200
commit202776694c2ae6b76e4e1d7b7f01d604f8d16089 (patch)
parent50ef0e2e9abe8dcaf9cbb54babec9134f4f0ca5f (diff)
romfs: use different way to generate fsid for BLOCK or MTD
[ Upstream commit f598f82e204ec0b17797caaf1b0311c52d43fb9a ] 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. Link: http://lkml.kernel.org/r/1482928596-115155-1-git-send-email-colyli@suse.de Signed-off-by: Coly Li <colyli@suse.de> Reported-by: Nong Li <nongli1031@gmail.com> Tested-by: Nong Li <nongli1031@gmail.com> Cc: Richard Weinberger <richard.weinberger@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 22 insertions, 1 deletions
diff --git a/fs/romfs/super.c b/fs/romfs/super.c
index 268733cda397..5f4f1882dc7d 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -74,6 +74,7 @@
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
+#include <linux/major.h>
#include "internal.h"
static struct kmem_cache *romfs_inode_cachep;
@@ -415,7 +416,22 @@ 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,
+ * 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;
@@ -488,6 +504,11 @@ 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;
+ /* Use same dev ID from the underlying mtdblock device */
+ if (sb->s_mtd)
+ sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
/* read the image superblock and check it */
rsb = kmalloc(512, GFP_KERNEL);
if (!rsb)