linux-ext4 - [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

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Date:   Tue, 30 Nov 2021 12:04:48 +0800
From:   zhanchengbin <zhanchengbin1@...wei.com>
To:     Theodore Ts'o <tytso@....edu>
CC:     <linux-ext4@...r.kernel.org>, <liuzhiqiang26@...wei.com>,
        <linfeilong@...wei.com>
Subject: [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

If there is a tmpfs with the same name as the disk, and mount before the 
disk,example:
	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0

Create a hard link /dev/sdd-ln for the disk and resize2fs it.The items in
/proc/mounts are traversed, When you get to tmpfs,file!=mnt->mnt_fsname,
Therefore, the stat(mnt->mnt_fsname, &st_buf) branch is used,However, the
values of file_rdev and st_buf.st_rdev are the same.As a result, the system
mistakenly considers that disk is mounted to /root/tmp.As a result,resize2fs
fails.

mkdir /root/tmp
mkdir /root/mnt
mkfs.ext4 -F -b 1024 -E "resize=10000000" /dev/sdd 32768
mount -t tmpfs /dev/sdd /root/tmp
mount /dev/sdd /root/mnt
ln /dev/sdd /dev/sdd-ln
resize2fs /dev/sdd-ln 6G

Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
Signed-off-by: guiyao@...wei.com
---
  lib/ext2fs/ismounted.c | 9 +++++++--
  1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index aee7d726..463a82a6 100644
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -98,6 +98,7 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  {
  	struct mntent 	*mnt;
  	struct stat	st_buf;
+	struct stat	dir_st_buf;
  	errcode_t	retval = 0;
  	dev_t		file_dev=0, file_rdev=0;
  	ino_t		file_ino=0;
@@ -144,8 +145,12 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
  			if (ext2fsP_is_disk_device(st_buf.st_mode)) {
  #ifndef __GNU__
-				if (file_rdev && (file_rdev == st_buf.st_rdev))
-					break;
+				if (file_rdev && (file_rdev == st_buf.st_rdev)) {
+					if (stat(mnt->mnt_dir, &dir_st_buf) != 0)
+						continue;
+					if (file_rdev == dir_st_buf.st_dev)
+						break;
+				}
  				if (check_loop_mounted(mnt->mnt_fsname,
  						st_buf.st_rdev, file_dev,
  						file_ino) == 1)
-- 
2.23.0