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Date: Sat, 14 Apr 2001 12:59:40 -0300 (BRT)
From: Marcelo Tosatti <marcelo@conectiva.com.br>
To: Christoph Rohland <cr@sap.com>
Cc: "Stephen C. Tweedie" <sct@redhat.com>,
        Linus Torvalds <torvalds@transmeta.com>,
        Rik van Riel <riel@conectiva.com.br>,
        lkml <linux-kernel@vger.kernel.org>
Subject: shmem_getpage_locked() / swapin_readahead() race in 2.4.4-pre3
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Hi, 

There is a nasty race between shmem_getpage_locked() and
swapin_readahead() with the new shmem code (introduced in 2.4.3-ac3 and
merged in the main tree in 2.4.4-pre3): 

shmem_getpage_locked() finds a page in the swapcache and moves it to the
pagecache as an shmem page, freeing the swapcache and the swap map entry
for this page. (which causes a BUG() in mm/shmem.c:353 since the swap
map entry is being used) 

In the meanwhile, swapin_readahead() is allocating a page and adding it to
the swapcache.

I don't see any clean fix for this one.

Suggestions ? 



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