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![Mel Gorman](/assets/img/avatar_default.png)
__GFP_WAIT has been used to identify atomic context in callers that hold spinlocks or are in interrupts. They are expected to be high priority and have access one of two watermarks lower than "min" which can be referred to as the "atomic reserve". __GFP_HIGH users get access to the first lower watermark and can be called the "high priority reserve". Over time, callers had a requirement to not block when fallback options were available. Some have abused __GFP_WAIT leading to a situation where an optimisitic allocation with a fallback option can access atomic reserves. This patch uses __GFP_ATOMIC to identify callers that are truely atomic, cannot sleep and have no alternative. High priority users continue to use __GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify callers that want to wake kswapd for background reclaim. __GFP_WAIT is redefined as a caller that is willing to enter direct reclaim and wake kswapd for background reclaim. This patch then converts a number of sites o __GFP_ATOMIC is used by callers that are high priority and have memory pools for those requests. GFP_ATOMIC uses this flag. o Callers that have a limited mempool to guarantee forward progress clear __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall into this category where kswapd will still be woken but atomic reserves are not used as there is a one-entry mempool to guarantee progress. o Callers that are checking if they are non-blocking should use the helper gfpflags_allow_blocking() where possible. This is because checking for __GFP_WAIT as was done historically now can trigger false positives. Some exceptions like dm-crypt.c exist where the code intent is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to flag manipulations. o Callers that built their own GFP flags instead of starting with GFP_KERNEL and friends now also need to specify __GFP_KSWAPD_RECLAIM. The first key hazard to watch out for is callers that removed __GFP_WAIT and was depending on access to atomic reserves for inconspicuous reasons. In some cases it may be appropriate for them to use __GFP_HIGH. The second key hazard is callers that assembled their own combination of GFP flags instead of starting with something like GFP_KERNEL. They may now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless if it's missed in most cases as other activity will wake kswapd. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
323 lines
7.7 KiB
C
323 lines
7.7 KiB
C
/*
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* connector.c
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*
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* 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/skbuff.h>
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#include <net/netlink.h>
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#include <linux/moduleparam.h>
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#include <linux/connector.h>
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#include <linux/slab.h>
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#include <linux/mutex.h>
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#include <linux/proc_fs.h>
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#include <linux/spinlock.h>
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#include <net/sock.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
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MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
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MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
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static struct cn_dev cdev;
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static int cn_already_initialized;
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/*
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* Sends mult (multiple) cn_msg at a time.
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*
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* msg->seq and msg->ack are used to determine message genealogy.
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* When someone sends message it puts there locally unique sequence
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* and random acknowledge numbers. Sequence number may be copied into
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* nlmsghdr->nlmsg_seq too.
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*
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* Sequence number is incremented with each message to be sent.
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*
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* If we expect a reply to our message then the sequence number in
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* received message MUST be the same as in original message, and
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* acknowledge number MUST be the same + 1.
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*
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* If we receive a message and its sequence number is not equal to the
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* one we are expecting then it is a new message.
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*
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* If we receive a message and its sequence number is the same as one
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* we are expecting but it's acknowledgement number is not equal to
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* the acknowledgement number in the original message + 1, then it is
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* a new message.
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*
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* If msg->len != len, then additional cn_msg messages are expected following
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* the first msg.
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*
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* The message is sent to, the portid if given, the group if given, both if
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* both, or if both are zero then the group is looked up and sent there.
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*/
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int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group,
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gfp_t gfp_mask)
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{
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struct cn_callback_entry *__cbq;
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unsigned int size;
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struct sk_buff *skb;
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struct nlmsghdr *nlh;
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struct cn_msg *data;
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struct cn_dev *dev = &cdev;
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u32 group = 0;
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int found = 0;
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if (portid || __group) {
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group = __group;
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} else {
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spin_lock_bh(&dev->cbdev->queue_lock);
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list_for_each_entry(__cbq, &dev->cbdev->queue_list,
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callback_entry) {
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if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
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found = 1;
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group = __cbq->group;
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break;
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}
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}
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spin_unlock_bh(&dev->cbdev->queue_lock);
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if (!found)
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return -ENODEV;
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}
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if (!portid && !netlink_has_listeners(dev->nls, group))
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return -ESRCH;
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size = sizeof(*msg) + len;
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skb = nlmsg_new(size, gfp_mask);
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if (!skb)
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return -ENOMEM;
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nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
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if (!nlh) {
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kfree_skb(skb);
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return -EMSGSIZE;
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}
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data = nlmsg_data(nlh);
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memcpy(data, msg, size);
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NETLINK_CB(skb).dst_group = group;
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if (group)
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return netlink_broadcast(dev->nls, skb, portid, group,
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gfp_mask);
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return netlink_unicast(dev->nls, skb, portid,
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!gfpflags_allow_blocking(gfp_mask));
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}
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EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
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/* same as cn_netlink_send_mult except msg->len is used for len */
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int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
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gfp_t gfp_mask)
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{
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return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask);
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}
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EXPORT_SYMBOL_GPL(cn_netlink_send);
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/*
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* Callback helper - queues work and setup destructor for given data.
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*/
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static int cn_call_callback(struct sk_buff *skb)
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{
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struct nlmsghdr *nlh;
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struct cn_callback_entry *i, *cbq = NULL;
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struct cn_dev *dev = &cdev;
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struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
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struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
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int err = -ENODEV;
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/* verify msg->len is within skb */
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nlh = nlmsg_hdr(skb);
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if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
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return -EINVAL;
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spin_lock_bh(&dev->cbdev->queue_lock);
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list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
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if (cn_cb_equal(&i->id.id, &msg->id)) {
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atomic_inc(&i->refcnt);
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cbq = i;
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break;
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}
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}
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spin_unlock_bh(&dev->cbdev->queue_lock);
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if (cbq != NULL) {
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cbq->callback(msg, nsp);
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kfree_skb(skb);
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cn_queue_release_callback(cbq);
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err = 0;
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}
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return err;
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}
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/*
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* Main netlink receiving function.
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*
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* It checks skb, netlink header and msg sizes, and calls callback helper.
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*/
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static void cn_rx_skb(struct sk_buff *__skb)
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{
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struct nlmsghdr *nlh;
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struct sk_buff *skb;
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int len, err;
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skb = skb_get(__skb);
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if (skb->len >= NLMSG_HDRLEN) {
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nlh = nlmsg_hdr(skb);
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len = nlmsg_len(nlh);
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if (len < (int)sizeof(struct cn_msg) ||
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skb->len < nlh->nlmsg_len ||
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len > CONNECTOR_MAX_MSG_SIZE) {
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kfree_skb(skb);
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return;
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}
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err = cn_call_callback(skb);
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if (err < 0)
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kfree_skb(skb);
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}
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}
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/*
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* Callback add routing - adds callback with given ID and name.
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* If there is registered callback with the same ID it will not be added.
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*
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* May sleep.
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*/
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int cn_add_callback(struct cb_id *id, const char *name,
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void (*callback)(struct cn_msg *,
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struct netlink_skb_parms *))
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{
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int err;
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struct cn_dev *dev = &cdev;
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if (!cn_already_initialized)
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return -EAGAIN;
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err = cn_queue_add_callback(dev->cbdev, name, id, callback);
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if (err)
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return err;
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return 0;
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}
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EXPORT_SYMBOL_GPL(cn_add_callback);
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/*
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* Callback remove routing - removes callback
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* with given ID.
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* If there is no registered callback with given
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* ID nothing happens.
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*
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* May sleep while waiting for reference counter to become zero.
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*/
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void cn_del_callback(struct cb_id *id)
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{
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struct cn_dev *dev = &cdev;
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cn_queue_del_callback(dev->cbdev, id);
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}
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EXPORT_SYMBOL_GPL(cn_del_callback);
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static int cn_proc_show(struct seq_file *m, void *v)
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{
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struct cn_queue_dev *dev = cdev.cbdev;
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struct cn_callback_entry *cbq;
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seq_printf(m, "Name ID\n");
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spin_lock_bh(&dev->queue_lock);
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list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
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seq_printf(m, "%-15s %u:%u\n",
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cbq->id.name,
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cbq->id.id.idx,
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cbq->id.id.val);
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}
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spin_unlock_bh(&dev->queue_lock);
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return 0;
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}
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static int cn_proc_open(struct inode *inode, struct file *file)
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{
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return single_open(file, cn_proc_show, NULL);
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}
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static const struct file_operations cn_file_ops = {
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.owner = THIS_MODULE,
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.open = cn_proc_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release
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};
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static struct cn_dev cdev = {
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.input = cn_rx_skb,
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};
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static int cn_init(void)
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{
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struct cn_dev *dev = &cdev;
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struct netlink_kernel_cfg cfg = {
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.groups = CN_NETLINK_USERS + 0xf,
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.input = dev->input,
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};
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dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
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if (!dev->nls)
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return -EIO;
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dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
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if (!dev->cbdev) {
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netlink_kernel_release(dev->nls);
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return -EINVAL;
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}
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cn_already_initialized = 1;
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proc_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
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return 0;
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}
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static void cn_fini(void)
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{
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struct cn_dev *dev = &cdev;
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cn_already_initialized = 0;
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remove_proc_entry("connector", init_net.proc_net);
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cn_queue_free_dev(dev->cbdev);
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netlink_kernel_release(dev->nls);
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}
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subsys_initcall(cn_init);
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module_exit(cn_fini);
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