[PATCH] btrfs-progs: mkfs: skip failed mount check

[Qu Wenruo <wqu@suse.com>]

[BUG]
There is a bug report that, with very weird mount status, there can be
some mount source which can not be accessed:

  /hana/shared/QD2/global/hdb/security/ssfs secfs2 500G 57G 444G 12% /hana/shared/QD2/global/hdb/security/ssfs

Strace shows we can not access the above mount source:

 131065 stat("/hana/shared/QD2/global/hdb/security/ssfs", 0x7ffed17b8e20) = -1 EACCES (Permission denied)

And lead to failed mount check:

 131065 write(2, "ERROR: ", 7)      = 7
 131065 write(2, "cannot check mount status of /de"..., 56) = 56
 131065 write(2, "\n", 1)        = 1

[CAUSE]
The mounted check is based on libblid, which gives the mount source, and
for non-btrfs mounts, we call path_is_reg_or_block_device() to check if
we even need to continue checking.

But in above case, the mount source is secfs2, and we can not access the
source.

So we error out causing the check_mounted() to return error.

[FIX]
There is never any guarantee we can access the mount source, but on the
other hand, I do not want to ignore all access failure for the mount
source.

So this patch would let test_status_for_mkfs() to only skip
check_mounted() error if @force_overwrite is true.

This would still keep the old strict checks on whether the target is
already mounted, but if the end user really knows that certain mount
source do not need to be checked, they can always pass "-f" option to
skip the false alerts.

Link: https://bugzilla.suse.com/show_bug.cgi?id=1223799
Reported-by: Jiri Belka <jiri.belka@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 mkfs/common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mkfs/common.c b/mkfs/common.c
index 3c48a6c120e7..314520397662 100644
--- a/mkfs/common.c
+++ b/mkfs/common.c
@@ -1129,6 +1129,12 @@ bool test_status_for_mkfs(const char *file, bool force_overwrite)
 	ret = check_mounted(file);
 	if (ret < 0) {
 		errno = -ret;
+		if (force_overwrite) {
+			error(
+		"cannot check mount status of %s (%m), skipping the check.",
+			      file);
+			return false;
+		}
 		error("cannot check mount status of %s: %m", file);
 		return true;
 	}
-- 
2.45.0