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mm: debug write deadlocks 

Allow CONFIG_DEBUG_VM to switch off the prefaulting logic, to simulate the
Makes the race much easier to hit.

This is useful for demonstration and testing purposes, but is removed in a
subsequent patch.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-10-16 01:24:56 -07:00 committed by Linus Torvalds
parent ae37461c70
commit 5fe1723706
1 changed files with 2 additions and 0 deletions
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2
mm/filemap.c
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@ -1878,6 +1878,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
if (maxlen > bytes) if (maxlen > bytes)
maxlen = bytes; maxlen = bytes;
#ifndef CONFIG_DEBUG_VM
/* /*
* Bring in the user page that we will copy from _first_. * Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the * Otherwise there's a nasty deadlock on copying from the
@ -1885,6 +1886,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
* up-to-date. * up-to-date.
*/ */
fault_in_pages_readable(buf, maxlen); fault_in_pages_readable(buf, maxlen);
#endif
page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec); page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
if (!page) { if (!page) {