vfs_op_exit(): assert that mnt_vfs_ops stays non-zero for unmount or suspend

[kib]

Summary

Tested by: pho

[mjg]

sys/kern/vfs_mount.c

1771

did you mean to put this after the decrement? as is it always passes since it is already asserted that the count is at least 1

i think for now it will most sense to change it into an if statement and include the same debug info as the already existing panic

[kib]

Correct the check, it must be > 1.
Add info similar to the above panic.

[kib]

sys/kern/vfs_mount.c

1771

So I have a question, why vfs_op_enter() and vfs_op_exit_locked() do panic() instead of using KASSERT? What makes these conditions so special?

BTW, panic() format string must not end with "\n", and lines in vfs_op_enter() are too long.

[mjg]

sys/kern/vfs_mount.c

1771

It follows other checks in the area, for example see all the panics in vfs_mount_destroy. I don't have a strong opinion one way or the other. This probably should get a MOUNTASSERT or whatever the name in a vain similar to VNASSERT.