When "read_only" is exposed as a mount option, it is redundant with the
standard option "ro" and gives users multiple ways to specify that a
bcachefs filesystem should be mounted read-only. This presents the risk
of having inconsistent options specified.
This can be seen when remounting a read-only filesystem in read-write
mode, using mount(8) from util-linux. Because mount(8) parses the
existing mount options from `/proc/mounts` and applies them when
remounting, it can end up applying both "read_only" and "rw":
$ mount img -o ro /mnt
$ strace mount -o remount,rw /mnt
...
fsconfig(4, FSCONFIG_SET_FLAG, "read_only", NULL, 0) = 0
fsconfig(4, FSCONFIG_SET_FLAG, "rw", NULL, 0) = 0
...
Making "read_only" no longer a mount option means this edge case cannot
occur.
Fixes: 62719cf33c3a ("bcachefs: Fix nochanges/read_only interaction")
Signed-off-by: Thomas Bertschinger <[email protected]>
---
fs/bcachefs/opts.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/bcachefs/opts.h b/fs/bcachefs/opts.h
index 25530e0bb2f3..f902793e1810 100644
--- a/fs/bcachefs/opts.h
+++ b/fs/bcachefs/opts.h
@@ -406,7 +406,7 @@ enum fsck_err_opts {
BCH2_NO_SB_OPT, BCH_SB_SECTOR, \
"offset", "Sector offset of superblock") \
x(read_only, u8, \
- OPT_FS|OPT_MOUNT, \
+ OPT_FS, \
OPT_BOOL(), \
BCH2_NO_SB_OPT, false, \
NULL, NULL) \
--
2.45.0
