[PATCH 4.19 063/125] ext4: handle option set by mount flags correctly

Greg Kroah-Hartman
2020-09-01T16:54:32Z

From: Lukas Czerner <lczerner@redhat.com>

[ Upstream commit f25391ebb475d3ffb3aa61bb90e3594c841749ef ]

Currently there is a problem with mount options that can be both set by
vfs using mount flags or by a string parsing in ext4.

i_version/iversion options gets lost after remount, for example

$ mount -o i_version /dev/pmem0 /mnt
$ grep pmem0 /proc/self/mountinfo | grep i_version
310 95 259:0 / /mnt rw,relatime shared:163 - ext4 /dev/pmem0 rw,seclabel,i_version
$ mount -o remount,ro /mnt
$ grep pmem0 /proc/self/mountinfo | grep i_version

nolazytime gets ignored by ext4 on remount, for example

$ mount -o lazytime /dev/pmem0 /mnt
$ grep pmem0 /proc/self/mountinfo | grep lazytime
310 95 259:0 / /mnt rw,relatime shared:163 - ext4 /dev/pmem0 rw,lazytime,seclabel
$ mount -o remount,nolazytime /mnt
$ grep pmem0 /proc/self/mountinfo | grep lazytime
310 95 259:0 / /mnt rw,relatime shared:163 - ext4 /dev/pmem0 rw,lazytime,seclabel

Fix it by applying the SB_LAZYTIME and SB_I_VERSION flags from *flags to
s_flags before we parse the option and use the resulting state of the
same flags in *flags at the end of successful remount.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/20200723150526.19931-1-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/super.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 23ef8fbdb582f..03ebb0b385467 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5249,7 +5249,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
{
struct ext4_super_block *es;
struct ext4_sb_info *sbi = EXT4_SB(sb);
- unsigned long old_sb_flags;
+ unsigned long old_sb_flags, vfs_flags;
struct ext4_mount_options old_opts;
int enable_quota = 0;
ext4_group_t g;
@@ -5292,6 +5292,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
if (sbi->s_journal && sbi->s_journal->j_task->io_context)
journal_ioprio = sbi->s_journal->j_task->io_context->ioprio;

+ /*
+ * Some options can be enabled by ext4 and/or by VFS mount flag
+ * either way we need to make sure it matches in both *flags and
+ * s_flags. Copy those selected flags from *flags to s_flags
+ */
+ vfs_flags = SB_LAZYTIME | SB_I_VERSION;
+ sb->s_flags = (sb->s_flags & ~vfs_flags) | (*flags & vfs_flags);
+
if (!parse_options(data, sb, NULL, &journal_ioprio, 1)) {
err = -EINVAL;
goto restore_opts;
@@ -5345,9 +5353,6 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
}

- if (*flags & SB_LAZYTIME)
- sb->s_flags |= SB_LAZYTIME;
-
if ((bool)(*flags & SB_RDONLY) != sb_rdonly(sb)) {
if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) {
err = -EROFS;
@@ -5487,7 +5492,13 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
}
#endif

- *flags = (*flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME);
+ /*
+ * Some options can be enabled by ext4 and/or by VFS mount flag
+ * either way we need to make sure it matches in both *flags and
+ * s_flags. Copy those selected flags from s_flags to *flags
+ */
+ *flags = (*flags & ~vfs_flags) | (sb->s_flags & vfs_flags);
+
ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data);
kfree(orig_data);
return 0;
--
2.25.1