nbd: set SOCK_MEMALLOC for access to PFMEMALLOC reserves (7f338fe4) · Commits · 戴 / test

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@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:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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) {

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