From: Andrew Morton <akpm@osdl.org>
Date: Wed, 27 Jul 2005 18:43:54 +0000 (-0700)
Subject: [PATCH] check_user_page_readable() deadlock fix
X-Git-Tag: v2.6.13-rc4~25^2~138
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1aaf18ff9de1f37bf674236fc0779c3aaa65b998;p=pandora-kernel.git

[PATCH] check_user_page_readable() deadlock fix

Fix bug identifued by Richard Purdie <rpurdie@rpsys.net>.

oprofile calls check_user_page_readable() from interrupt context, so we
deadlock over various VFS locks.

But check_user_page_readable() doesn't imply either a read or a write of the
page's contents.  Change __follow_page() so that check_user_page_readable()
can tell __follow_page() that we're not accessing the page's contents, and use
that info to avoid the troublesome lock-takings.

Also, make follow_page() inline for the single callsite in memory.c to save a
bit of stack space.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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