If fs is frozen after mount and before the first file open, the
update of s_last_mounted bypasses freeze protection and prints out
a WARNING splat:
$ mount /vdf
$ fsfreeze -f /vdf
$ cat /vdf/foo
[ 31.578555] WARNING: CPU: 1 PID: 1415 at
fs/ext4/ext4_jbd2.c:53 ext4_journal_check_start+0x48/0x82
[ 31.614016] Call Trace:
[ 31.614997] __ext4_journal_start_sb+0xe4/0x1a4
[ 31.616771] ? ext4_file_open+0xb6/0x189
[ 31.618094] ext4_file_open+0xb6/0x189
This fix might not be free of open vs. freeze race, but it closes
a big hole.
[backport hint: to apply to stable tree, just need to repace
sb_rdonly(sb) with (sb->s_flags & MS_RDONLY)]
Fixes: bc0b0d6d69ee ("ext4: update the s_last_mounted field in the
superblock")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/ext4/file.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index fb6f023622fe..b78e5e6c0e51 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -392,8 +392,8 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
return -EIO;
- if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
- !sb_rdonly(sb))) {
+ if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED)) &&
+ !sb_rdonly(sb) && sb->s_writers.frozen == SB_UNFROZEN) {
sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
/*
* Sample where the filesystem has been mounted and
--
2.7.4
