Re: [patch] truncate fixes

From: Andrea Arcangeli (
Date: Sun Jan 06 2002 - 22:16:36 EST

On Sun, Jan 06, 2002 at 06:53:30PM -0800, Andrew Morton wrote:
> Andrea Arcangeli wrote:
> >
> > I prefer my fix that simply recalls the ->truncate callback if -ENOSPC
> > is returned by prepare_write. vmtruncate seems way overkill,
> No opinion on that here. This is what was in -ac. Perhaps Al can
> comment?
> > and after
> > calling ->truncate the __block_prepare_changes above won't be necessary
> > because the leftover will be correctly deallocated (no need to clear
> > them out and to mark them dirty, they will just go away before any
> > readpage can see them).
> No, this code is needed if the write is _inside_ i_size, to an
> uninstantiated block. truncate won't remove those blocks, and we've
> gone and added them to the file.

I see, I got mistaken because here we're not in a i_sem-less writepage, so
in those cases I wanted to always deallocate the blocks rather than
lefting zeroed leftovers. if the leftover blocks are over i_size (common
case I was thinking about incidentally :) that's automatica with
->truncate, but if they aren't over i_size that's not enough and we miss
a lowlevel API to decallocate a range of blocks, so your patch is the
only way indeed.

> -

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