[PATCH] Send quota messages via netlink

[Jan Kara <jack@suse.cz>]

  Hello,

  I'm sending rediffed patch implementing sending of quota messages via netlink
interface (some rationale in patch description). I've already posted it to
LKML some time ago and there were no objections, so I guess it's fine to put
it to -mm. Andrew, would you be so kind? Thanks.
  Userspace deamon reading the messages from the kernel and sending them to
dbus and/or user console is also written (it's part of quota-tools). The
only remaining problem is there are a few changes needed to libnl needed for
the userspace daemon. They were basically acked by the maintainer but it
seems he has not merged the patches yet. So this will take a bit more time.

									Honza
-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs

Implement sending of quota messages via netlink interface. The advantage is
that in userspace we can better decide what to do with the message - for
example display a dialogue in your X session or just write the message to the
console. As a bonus, we can get rid of problems with console locking deep
inside filesystem code once we remove the old printing mechanism.

Signed-off-by: Jan Kara <jack@suse.cz>

diff -rupX /home/jack/.kerndiffexclude linux-2.6.23-rc4/fs/dquot.c linux-2.6.23-rc4-1-quota_messages/fs/dquot.c
--- linux-2.6.23-rc4/fs/dquot.c	2007-08-28 14:08:51.000000000 +0200
+++ linux-2.6.23-rc4-1-quota_messages/fs/dquot.c	2007-08-28 14:16:26.000000000 +0200
@@ -79,6 +79,10 @@
 #include <linux/capability.h>
 #include <linux/quotaops.h>
 #include <linux/writeback.h> /* for inode_lock, oddly enough.. */
+#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
+#include <net/netlink.h>
+#include <net/genetlink.h>
+#endif
 
 #include <asm/uaccess.h>
 
@@ -823,6 +827,7 @@ static inline void dquot_decr_space(stru
 	clear_bit(DQ_BLKS_B, &dquot->dq_flags);
 }
 
+#ifdef CONFIG_PRINT_QUOTA_WARNING
 static int flag_print_warnings = 1;
 
 static inline int need_print_warning(struct dquot *dquot)
@@ -839,22 +844,15 @@ static inline int need_print_warning(str
 	return 0;
 }
 
-/* Values of warnings */
-#define NOWARN 0
-#define IHARDWARN 1
-#define ISOFTLONGWARN 2
-#define ISOFTWARN 3
-#define BHARDWARN 4
-#define BSOFTLONGWARN 5
-#define BSOFTWARN 6
-
 /* Print warning to user which exceeded quota */
 static void print_warning(struct dquot *dquot, const char warntype)
 {
 	char *msg = NULL;
 	struct tty_struct *tty;
-	int flag = (warntype == BHARDWARN || warntype == BSOFTLONGWARN) ? DQ_BLKS_B :
-	  ((warntype == IHARDWARN || warntype == ISOFTLONGWARN) ? DQ_INODES_B : 0);
+	int flag = (warntype == QUOTA_NL_BHARDWARN ||
+		warntype == QUOTA_NL_BSOFTLONGWARN) ? DQ_BLKS_B :
+		((warntype == QUOTA_NL_IHARDWARN ||
+		warntype == QUOTA_NL_ISOFTLONGWARN) ? DQ_INODES_B : 0);
 
 	if (!need_print_warning(dquot) || (flag && test_and_set_bit(flag, &dquot->dq_flags)))
 		return;
@@ -864,28 +862,28 @@ static void print_warning(struct dquot *
 	if (!tty)
 		goto out_lock;
 	tty_write_message(tty, dquot->dq_sb->s_id);
-	if (warntype == ISOFTWARN || warntype == BSOFTWARN)
+	if (warntype == QUOTA_NL_ISOFTWARN || warntype == QUOTA_NL_BSOFTWARN)
 		tty_write_message(tty, ": warning, ");
 	else
 		tty_write_message(tty, ": write failed, ");
 	tty_write_message(tty, quotatypes[dquot->dq_type]);
 	switch (warntype) {
-		case IHARDWARN:
+		case QUOTA_NL_IHARDWARN:
 			msg = " file limit reached.\r\n";
 			break;
-		case ISOFTLONGWARN:
+		case QUOTA_NL_ISOFTLONGWARN:
 			msg = " file quota exceeded too long.\r\n";
 			break;
-		case ISOFTWARN:
+		case QUOTA_NL_ISOFTWARN:
 			msg = " file quota exceeded.\r\n";
 			break;
-		case BHARDWARN:
+		case QUOTA_NL_BHARDWARN:
 			msg = " block limit reached.\r\n";
 			break;
-		case BSOFTLONGWARN:
+		case QUOTA_NL_BSOFTLONGWARN:
 			msg = " block quota exceeded too long.\r\n";
 			break;
-		case BSOFTWARN:
+		case QUOTA_NL_BSOFTWARN:
 			msg = " block quota exceeded.\r\n";
 			break;
 	}
@@ -893,14 +891,89 @@ static void print_warning(struct dquot *
 out_lock:
 	mutex_unlock(&tty_mutex);
 }
+#endif
+
+#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
+
+/* Size of quota netlink message - actually an upperbound for buffer size */
+#define QUOTA_NL_MSG_SIZE 32
+
+/* Netlink family structure for quota */
+static struct genl_family quota_genl_family = {
+	.id = GENL_ID_GENERATE,
+	.hdrsize = 0,
+	.name = "VFS_DQUOT",
+	.version = 1,
+	.maxattr = QUOTA_NL_A_MAX,
+};
+
+/* Send warning to userspace about user which exceeded quota */
+static void send_warning(const struct dquot *dquot, const char warntype)
+{
+	static unsigned long seq;
+	struct sk_buff *skb;
+	void *msg_head;
+	int ret;
+
+	skb = genlmsg_new(QUOTA_NL_MSG_SIZE, GFP_NOFS);
+	if (!skb) {
+		printk(KERN_ERR
+		  "VFS: Not enough memory to send quota warning.\n");
+		return;
+	}
+	msg_head = genlmsg_put(skb, 0, seq++, &quota_genl_family, 0, QUOTA_NL_C_WARNING);
+	if (!msg_head) {
+		printk(KERN_ERR
+		  "VFS: Cannot store netlink header in quota warning.\n");
+		goto err_out;
+	}
+	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, dquot->dq_type);
+	if (ret)
+		goto attr_err_out;
+	ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID, dquot->dq_id);
+	if (ret)
+		goto attr_err_out;
+	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
+	if (ret)
+		goto attr_err_out;
+	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR,
+		MAJOR(dquot->dq_sb->s_dev));
+	if (ret)
+		goto attr_err_out;
+	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR,
+		MINOR(dquot->dq_sb->s_dev));
+	if (ret)
+		goto attr_err_out;
+	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current->user->uid);
+	if (ret)
+		goto attr_err_out;
+	genlmsg_end(skb, msg_head);
+
+	ret = genlmsg_multicast(skb, 0, quota_genl_family.id, GFP_NOFS);
+	if (ret < 0 && ret != -ESRCH)
+		printk(KERN_ERR
+			"VFS: Failed to send notification message: %d\n", ret);
+	return;
+attr_err_out:
+	printk(KERN_ERR "VFS: Failed to compose quota message: %d\n", ret);
+err_out:
+	kfree_skb(skb);
+}
+#endif
 
 static inline void flush_warnings(struct dquot **dquots, char *warntype)
 {
 	int i;
 
 	for (i = 0; i < MAXQUOTAS; i++)
-		if (dquots[i] != NODQUOT && warntype[i] != NOWARN)
+		if (dquots[i] != NODQUOT && warntype[i] != QUOTA_NL_NOWARN) {
+#ifdef CONFIG_PRINT_QUOTA_WARNING
 			print_warning(dquots[i], warntype[i]);
+#endif
+#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
+			send_warning(dquots[i], warntype[i]);
+#endif
+		}
 }
 
 static inline char ignore_hardlimit(struct dquot *dquot)
@@ -914,14 +987,14 @@ static inline char ignore_hardlimit(stru
 /* needs dq_data_lock */
 static int check_idq(struct dquot *dquot, ulong inodes, char *warntype)
 {
-	*warntype = NOWARN;
+	*warntype = QUOTA_NL_NOWARN;
 	if (inodes <= 0 || test_bit(DQ_FAKE_B, &dquot->dq_flags))
 		return QUOTA_OK;
 
 	if (dquot->dq_dqb.dqb_ihardlimit &&
 	   (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_ihardlimit &&
             !ignore_hardlimit(dquot)) {
-		*warntype = IHARDWARN;
+		*warntype = QUOTA_NL_IHARDWARN;
 		return NO_QUOTA;
 	}
 
@@ -929,14 +1002,14 @@ static int check_idq(struct dquot *dquot
 	   (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_isoftlimit &&
 	    dquot->dq_dqb.dqb_itime && get_seconds() >= dquot->dq_dqb.dqb_itime &&
             !ignore_hardlimit(dquot)) {
-		*warntype = ISOFTLONGWARN;
+		*warntype = QUOTA_NL_ISOFTLONGWARN;
 		return NO_QUOTA;
 	}
 
 	if (dquot->dq_dqb.dqb_isoftlimit &&
 	   (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_isoftlimit &&
 	    dquot->dq_dqb.dqb_itime == 0) {
-		*warntype = ISOFTWARN;
+		*warntype = QUOTA_NL_ISOFTWARN;
 		dquot->dq_dqb.dqb_itime = get_seconds() + sb_dqopt(dquot->dq_sb)->info[dquot->dq_type].dqi_igrace;
 	}
 
@@ -946,7 +1019,7 @@ static int check_idq(struct dquot *dquot
 /* needs dq_data_lock */
 static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *warntype)
 {
-	*warntype = 0;
+	*warntype = QUOTA_NL_NOWARN;
 	if (space <= 0 || test_bit(DQ_FAKE_B, &dquot->dq_flags))
 		return QUOTA_OK;
 
@@ -954,7 +1027,7 @@ static int check_bdq(struct dquot *dquot
 	   toqb(dquot->dq_dqb.dqb_curspace + space) > dquot->dq_dqb.dqb_bhardlimit &&
             !ignore_hardlimit(dquot)) {
 		if (!prealloc)
-			*warntype = BHARDWARN;
+			*warntype = QUOTA_NL_BHARDWARN;
 		return NO_QUOTA;
 	}
 
@@ -963,7 +1036,7 @@ static int check_bdq(struct dquot *dquot
 	    dquot->dq_dqb.dqb_btime && get_seconds() >= dquot->dq_dqb.dqb_btime &&
             !ignore_hardlimit(dquot)) {
 		if (!prealloc)
-			*warntype = BSOFTLONGWARN;
+			*warntype = QUOTA_NL_BSOFTLONGWARN;
 		return NO_QUOTA;
 	}
 
@@ -971,7 +1044,7 @@ static int check_bdq(struct dquot *dquot
 	   toqb(dquot->dq_dqb.dqb_curspace + space) > dquot->dq_dqb.dqb_bsoftlimit &&
 	    dquot->dq_dqb.dqb_btime == 0) {
 		if (!prealloc) {
-			*warntype = BSOFTWARN;
+			*warntype = QUOTA_NL_BSOFTWARN;
 			dquot->dq_dqb.dqb_btime = get_seconds() + sb_dqopt(dquot->dq_sb)->info[dquot->dq_type].dqi_bgrace;
 		}
 		else
@@ -1066,7 +1139,7 @@ out_add:
 		return QUOTA_OK;
 	}
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
-		warntype[cnt] = NOWARN;
+		warntype[cnt] = QUOTA_NL_NOWARN;
 
 	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
 	if (IS_NOQUOTA(inode)) {	/* Now we can do reliable test... */
@@ -1112,7 +1185,7 @@ int dquot_alloc_inode(const struct inode
 	if (IS_NOQUOTA(inode))
 		return QUOTA_OK;
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
-		warntype[cnt] = NOWARN;
+		warntype[cnt] = QUOTA_NL_NOWARN;
 	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
 	if (IS_NOQUOTA(inode)) {
 		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
@@ -1234,7 +1307,7 @@ int dquot_transfer(struct inode *inode, 
 	/* Clear the arrays */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		transfer_to[cnt] = transfer_from[cnt] = NODQUOT;
-		warntype[cnt] = NOWARN;
+		warntype[cnt] = QUOTA_NL_NOWARN;
 	}
 	down_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
 	/* Now recheck reliably when holding dqptr_sem */
@@ -1808,6 +1881,7 @@ static ctl_table fs_dqstats_table[] = {
 		.mode		= 0444,
 		.proc_handler	= &proc_dointvec,
 	},
+#ifdef CONFIG_PRINT_QUOTA_WARNING
 	{
 		.ctl_name	= FS_DQ_WARNINGS,
 		.procname	= "warnings",
@@ -1816,6 +1890,7 @@ static ctl_table fs_dqstats_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+#endif
 	{ .ctl_name = 0 },
 };
 
@@ -1877,6 +1952,11 @@ static int __init dquot_init(void)
 
 	register_shrinker(&dqcache_shrinker);
 
+#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
+	if (genl_register_family(&quota_genl_family) != 0)
+		printk(KERN_ERR "VFS: Failed to create quota netlink interface.\n");
+#endif
+
 	return 0;
 }
 module_init(dquot_init);
diff -rupX /home/jack/.kerndiffexclude linux-2.6.23-rc4/fs/Kconfig linux-2.6.23-rc4-1-quota_messages/fs/Kconfig
--- linux-2.6.23-rc4/fs/Kconfig	2007-08-28 14:08:50.000000000 +0200
+++ linux-2.6.23-rc4-1-quota_messages/fs/Kconfig	2007-08-28 14:16:26.000000000 +0200
@@ -537,6 +537,24 @@ config QUOTA
 	  with the quota tools. Probably the quota support is only useful for
 	  multi user systems. If unsure, say N.
 
+config QUOTA_NETLINK_INTERFACE
+	bool "Report quota messages through netlink interface"
+	depends on QUOTA && NET
+	help
+	  If you say Y here, quota warnings (about exceeding softlimit, reaching
+	  hardlimit, etc.) will be reported through netlink interface. If unsure,
+	  say Y.
+
+config PRINT_QUOTA_WARNING
+	bool "Print quota warnings to console (OBSOLETE)"
+	depends on QUOTA
+	default y
+	help
+	  If you say Y here, quota warnings (about exceeding softlimit, reaching
+	  hardlimit, etc.) will be printed to the process' controlling terminal.
+	  Note that this behavior is currently deprecated and may go away in
+	  future. Please use notification via netlink socket instead.
+
 config QFMT_V1
 	tristate "Old quota format support"
 	depends on QUOTA
diff -rupX /home/jack/.kerndiffexclude linux-2.6.23-rc4/include/linux/quota.h linux-2.6.23-rc4-1-quota_messages/include/linux/quota.h
--- linux-2.6.23-rc4/include/linux/quota.h	2007-07-16 17:47:29.000000000 +0200
+++ linux-2.6.23-rc4-1-quota_messages/include/linux/quota.h	2007-08-28 14:24:02.000000000 +0200
@@ -128,6 +128,37 @@ struct if_dqinfo {
 	__u32 dqi_valid;
 };
 
+/*
+ * Definitions for quota netlink interface
+ */
+#define QUOTA_NL_NOWARN 0
+#define QUOTA_NL_IHARDWARN 1		/* Inode hardlimit reached */
+#define QUOTA_NL_ISOFTLONGWARN 2 	/* Inode grace time expired */
+#define QUOTA_NL_ISOFTWARN 3		/* Inode softlimit reached */
+#define QUOTA_NL_BHARDWARN 4		/* Block hardlimit reached */
+#define QUOTA_NL_BSOFTLONGWARN 5	/* Block grace time expired */
+#define QUOTA_NL_BSOFTWARN 6		/* Block softlimit reached */
+
+enum {
+	QUOTA_NL_C_UNSPEC,
+	QUOTA_NL_C_WARNING,
+	__QUOTA_NL_C_MAX,
+};
+#define QUOTA_NL_C_MAX (__QUOTA_NL_C_MAX - 1)
+
+enum {
+	QUOTA_NL_A_UNSPEC,
+	QUOTA_NL_A_QTYPE,
+	QUOTA_NL_A_EXCESS_ID,
+	QUOTA_NL_A_WARNING,
+	QUOTA_NL_A_DEV_MAJOR,
+	QUOTA_NL_A_DEV_MINOR,
+	QUOTA_NL_A_CAUSED_ID,
+	__QUOTA_NL_A_MAX,
+};
+#define QUOTA_NL_A_MAX (__QUOTA_NL_A_MAX - 1)
+
+
 #ifdef __KERNEL__
 #include <linux/spinlock.h>
 #include <linux/rwsem.h>