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Commit 7f338fe4 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

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: default avatarMel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 381760ea

drivers/block/nbd.c

+5 −1
Original line number Diff line number Diff line
@@ -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) {