From babe30fe8db62b79f7e3df4144acc344b3672f60 Mon Sep 17 00:00:00 2001 From: Thomas Bertschinger Date: Sun, 26 May 2024 13:08:20 -0600 Subject: [PATCH] bcachefs: don't expose "read_only" as a mount option 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 Signed-off-by: Kent Overstreet --- 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 b197ec90d4cb..c9da6267894b 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) \