linux-kernel - [PATCH 4/6] kill-the-BKL/reiserfs: release the write lock inside get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri,  1 May 2009 04:44:20 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jeff Mahoney <jeffm@...e.com>,
	ReiserFS Development List <reiserfs-devel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>,
	Alexander Beregalov <a.beregalov@...il.com>,
	Alessio Igor Bogani <abogani@...ware.it>,
	Jonathan Corbet <corbet@....net>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 4/6] kill-the-BKL/reiserfs: release the write lock inside get_neighbors()

get_neighbors() is used to get the left and/or right blocks
against a given one in order to balance a tree.

sb_bread() is used to read the buffer of these neighors blocks and
while it waits for this operation, it might sleep.

The bkl was released at this point, and then we can also release
the write lock before calling sb_bread().

This is safe because if the filesystem is changed after this
lock release, the function returns REPEAT_SEARCH (aka SCHEDULE_OCCURRED
in the function header comments) in order to repeat the neighbhor
research.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@...e.com>
Cc: Chris Mason <chris.mason@...cle.com>
Cc: Alexander Beregalov <a.beregalov@...il.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 fs/reiserfs/fix_node.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/fs/reiserfs/fix_node.c b/fs/reiserfs/fix_node.c
index bf5f2cb..3a685e3 100644
--- a/fs/reiserfs/fix_node.c
+++ b/fs/reiserfs/fix_node.c
@@ -1971,7 +1971,9 @@ static int get_neighbors(struct tree_balance *tb, int h)
 		     tb->FL[h]) ? tb->lkey[h] : B_NR_ITEMS(tb->
 								       FL[h]);
 		son_number = B_N_CHILD_NUM(tb->FL[h], child_position);
+		reiserfs_write_unlock(sb);
 		bh = sb_bread(sb, son_number);
+		reiserfs_write_lock(sb);
 		if (!bh)
 			return IO_ERROR;
 		if (FILESYSTEM_CHANGED_TB(tb)) {
@@ -2009,7 +2011,9 @@ static int get_neighbors(struct tree_balance *tb, int h)
 		child_position =
 		    (bh == tb->FR[h]) ? tb->rkey[h] + 1 : 0;
 		son_number = B_N_CHILD_NUM(tb->FR[h], child_position);
+		reiserfs_write_unlock(sb);
 		bh = sb_bread(sb, son_number);
+		reiserfs_write_lock(sb);
 		if (!bh)
 			return IO_ERROR;
 		if (FILESYSTEM_CHANGED_TB(tb)) {
-- 
1.6.2.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/