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| 1 | /* |
| 2 | * linux/ipc/ipcns_notifier.c |
| 3 | * Copyright (C) 2007 BULL SA. Nadia Derbey |
| 4 | * |
| 5 | * Notification mechanism for ipc namespaces: |
| 6 | * The callback routine registered in the memory chain invokes the ipcns |
| 7 | * notifier chain with the IPCNS_MEMCHANGED event. |
| 8 | * Each callback routine registered in the ipcns namespace recomputes msgmni |
| 9 | * for the owning namespace. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/msg.h> |
| 13 | #include <linux/rcupdate.h> |
| 14 | #include <linux/notifier.h> |
| 15 | #include <linux/nsproxy.h> |
| 16 | #include <linux/ipc_namespace.h> |
| 17 | |
| 18 | #include "util.h" |
| 19 | |
| 20 | |
| 21 | |
| 22 | static BLOCKING_NOTIFIER_HEAD(ipcns_chain); |
| 23 | |
| 24 | |
| 25 | static int ipcns_callback(struct notifier_block *self, |
| 26 | unsigned long action, void *arg) |
| 27 | { |
| 28 | struct ipc_namespace *ns; |
| 29 | |
| 30 | switch (action) { |
| 31 | case IPCNS_MEMCHANGED: /* amount of lowmem has changed */ |
| 32 | case IPCNS_CREATED: |
| 33 | case IPCNS_REMOVED: |
| 34 | /* |
| 35 | * It's time to recompute msgmni |
| 36 | */ |
| 37 | ns = container_of(self, struct ipc_namespace, ipcns_nb); |
| 38 | /* |
| 39 | * No need to get a reference on the ns: the 1st job of |
| 40 | * free_ipc_ns() is to unregister the callback routine. |
| 41 | * blocking_notifier_chain_unregister takes the wr lock to do |
| 42 | * it. |
| 43 | * When this callback routine is called the rd lock is held by |
| 44 | * blocking_notifier_call_chain. |
| 45 | * So the ipc ns cannot be freed while we are here. |
| 46 | */ |
| 47 | recompute_msgmni(ns); |
| 48 | break; |
| 49 | default: |
| 50 | break; |
| 51 | } |
| 52 | |
| 53 | return NOTIFY_OK; |
| 54 | } |
| 55 | |
| 56 | int register_ipcns_notifier(struct ipc_namespace *ns) |
| 57 | { |
| 58 | int rc; |
| 59 | |
| 60 | memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb)); |
| 61 | ns->ipcns_nb.notifier_call = ipcns_callback; |
| 62 | ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI; |
| 63 | rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb); |
| 64 | if (!rc) |
| 65 | ns->auto_msgmni = 1; |
| 66 | return rc; |
| 67 | } |
| 68 | |
| 69 | int cond_register_ipcns_notifier(struct ipc_namespace *ns) |
| 70 | { |
| 71 | int rc; |
| 72 | |
| 73 | memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb)); |
| 74 | ns->ipcns_nb.notifier_call = ipcns_callback; |
| 75 | ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI; |
| 76 | rc = blocking_notifier_chain_cond_register(&ipcns_chain, |
| 77 | &ns->ipcns_nb); |
| 78 | if (!rc) |
| 79 | ns->auto_msgmni = 1; |
| 80 | return rc; |
| 81 | } |
| 82 | |
| 83 | void unregister_ipcns_notifier(struct ipc_namespace *ns) |
| 84 | { |
| 85 | blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb); |
| 86 | ns->auto_msgmni = 0; |
| 87 | } |
| 88 | |
| 89 | int ipcns_notify(unsigned long val) |
| 90 | { |
| 91 | return blocking_notifier_call_chain(&ipcns_chain, val, NULL); |
| 92 | } |
| 93 |
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