Re: 1352 NUL bytes at the end of a page? (was Re: Assertion `s &&s->tree' failed: The saga continues.)

[Andrew Morton]

Linus Torvalds <torvalds@xxxxxxxx> wrote:
>
> Andrew, the obvious culprit would be the memset() in fs/buffer.c 
>  (block_write_full_page() 

There is one race.

If an application does mmap(MAP_SHARED) of, say, a 2048 byte file and then
extends it:

	p = mmap(..., fd, ...);
	ftructate(fd, 4096);
	p[3000] = 1;

A racing block_write_full_page() could fail to notice the extended i_size
and would decide to zap those 2048 bytes anyway.	
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