linux-kernel - [PATCH 14/16] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves

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:	Mon, 16 Apr 2012 13:17:01 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>, Neil Brown <neilb@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Christie <michaelc@...wisc.edu>,
	Eric B Munson <emunson@...bm.net>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 14/16] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves

Set SOCK_MEMALLOC on the NBD socket to allow access to PFMEMALLOC
reserves so pages backed by NBD, particularly if swap related, can
be cleaned to prevent the machine being deadlocked. It is still
possible that the PFMEMALLOC reserves get depleted resulting in
deadlock but this can be resolved by the administrator by increasing
min_free_kbytes.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 drivers/block/nbd.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 061427a75d..76bc96f 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -154,6 +154,7 @@ static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
 	struct msghdr msg;
 	struct kvec iov;
 	sigset_t blocked, oldset;
+	unsigned long pflags = current->flags;
 
 	if (unlikely(!sock)) {
 		dev_err(disk_to_dev(nbd->disk),
@@ -167,8 +168,9 @@ static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
 	siginitsetinv(&blocked, sigmask(SIGKILL));
 	sigprocmask(SIG_SETMASK, &blocked, &oldset);
 
+	current->flags |= PF_MEMALLOC;
 	do {
-		sock->sk->sk_allocation = GFP_NOIO;
+		sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC;
 		iov.iov_base = buf;
 		iov.iov_len = size;
 		msg.msg_name = NULL;
@@ -214,6 +216,7 @@ static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
 	} while (size > 0);
 
 	sigprocmask(SIG_SETMASK, &oldset, NULL);
+	tsk_restore_flags(current, pflags, PF_MEMALLOC);
 
 	return result;
 }
@@ -405,6 +408,7 @@ static int nbd_do_it(struct nbd_device *nbd)
 
 	BUG_ON(nbd->magic != NBD_MAGIC);
 
+	sk_set_memalloc(nbd->sock->sk);
 	nbd->pid = task_pid_nr(current);
 	ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
 	if (ret) {
-- 
1.7.9.2

--
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/