Ext2fs locking

From: Benhanokh Gabriel (gabrielo@cs.huji.ac.il)
Date: Wed Apr 26 2000 - 08:52:52 EST


i'm trying to write a pure block allocator(i.e. it only allocates
blocks, and doesn't read any of them) for the ext2fs.

to do this i need to lock the blocks-bitmap of the blocks-group i'm
working on before alloacting.

the problem is that i failed to find a way to lock ONLY the
blocks-bitmap, in the ext2fs code i saw that the only lock they use is
lock_super which locks the whole super-block( is it ?).
this seems like an over-kill for this stuff.

one more thing
the lock_super code is as follows ( extracted from locks.h )

extern inline void lock_super(struct super_block * sb)
        if (sb->s_lock)
        sb->s_lock = 1;

this code doesn't seem to implement a real lock, so does this code
assumes atomicy of this call ?
is it depends on the fact that only one process can be at the kernel at
a time?
how can i force a lock which will work on SMP machine?

Gabriel Benhanokh

please CC me for any answer as i'm not register to the mailing list (
slow connection...)

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