Re: lock/unlock_super and inode bitmaps.

Theodore Y. Ts'o (tytso@mit.edu)
Wed, 27 Oct 1999 17:26:14 -0400


Date: Wed, 27 Oct 1999 16:29:02 +0100 (BST)
From: Tigran Aivazian <tigran@sco.COM>

Another case, where I really don't like the way Linux relies on big kernel
lock is registering/unregistering filesystems. Currently it is only done
either in initialization context or from module_init/cleanup which means
we either don't need a lock or have a big kernel lock respectively. I
would have preferred to see file_systems protected by a read-write lock
whereby register/unregister take a write and all others take a read. When
I wanted to do it I hit the obstacle - the way mount_root() walks through
it sleeping on the way (in read_super())...

Umm... it's not like registering/unregistering filesystems is a very
common activity. If we need to take the Big Lock while we register a
filesystem, it's hardly going to hurt anyone. It's not like this is
done thousands of times a second. :-)

- Ted

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