quota: send messages via netlink

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>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/filesystems/quota.txt b/Documentation/filesystems/quota.txt
new file mode 100644 (file)
index 0000000..a590c40
--- /dev/null
+++ b/Documentation/filesystems/quota.txt
@@ -0,0 +1,59 @@
+
+Quota subsystem
+===============
+
+Quota subsystem allows system administrator to set limits on used space and
+number of used inodes (inode is a filesystem structure which is associated
+with each file or directory) for users and/or groups. For both used space and
+number of used inodes there are actually two limits. The first one is called
+softlimit and the second one hardlimit.  An user can never exceed a hardlimit
+for any resource. User is allowed to exceed softlimit but only for limited
+period of time. This period is called "grace period" or "grace time". When
+grace time is over, user is not able to allocate more space/inodes until he
+frees enough of them to get below softlimit.
+
+Quota limits (and amount of grace time) are set independently for each
+filesystem.
+
+For more details about quota design, see the documentation in quota-tools package
+(http://sourceforge.net/projects/linuxquota).
+
+Quota netlink interface
+=======================
+When user exceeds a softlimit, runs out of grace time or reaches hardlimit,
+quota subsystem traditionally printed a message to the controlling terminal of
+the process which caused the excess. This method has the disadvantage that
+when user is using a graphical desktop he usually cannot see the message.
+Thus quota netlink interface has been designed to pass information about
+the above events to userspace. There they can be captured by an application
+and processed accordingly.
+
+The interface uses generic netlink framework (see
+http://lwn.net/Articles/208755/ and http://people.suug.ch/~tgr/libnl/ for more
+details about this layer). The name of the quota generic netlink interface
+is "VFS_DQUOT". Definitions of constants below are in <linux/quota.h>.
+  Currently, the interface supports only one message type QUOTA_NL_C_WARNING.
+This command is used to send a notification about any of the above mentioned
+events. Each message has six attributes. These are (type of the argument is
+in parentheses):
+        QUOTA_NL_A_QTYPE (u32)
+         - type of quota being exceeded (one of USRQUOTA, GRPQUOTA)
+        QUOTA_NL_A_EXCESS_ID (u64)
+         - UID/GID (depends on quota type) of user / group whose limit
+           is being exceeded.
+        QUOTA_NL_A_CAUSED_ID (u64)
+         - UID of a user who caused the event
+        QUOTA_NL_A_WARNING (u32)
+         - what kind of limit is exceeded:
+               QUOTA_NL_IHARDWARN - inode hardlimit
+               QUOTA_NL_ISOFTLONGWARN - inode softlimit is exceeded longer
+                 than given grace period
+               QUOTA_NL_ISOFTWARN - inode softlimit
+               QUOTA_NL_BHARDWARN - space (block) hardlimit
+               QUOTA_NL_BSOFTLONGWARN - space (block) softlimit is exceeded
+                 longer than given grace period.
+               QUOTA_NL_BSOFTWARN - space (block) softlimit
+        QUOTA_NL_A_DEV_MAJOR (u32)
+         - major number of a device with the affected filesystem
+        QUOTA_NL_A_DEV_MINOR (u32)
+         - minor number of a device with the affected filesystem

diff --git a/fs/Kconfig b/fs/Kconfig
index f0df9a2..dc06033 100644 (file)
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -534,6 +534,24 @@ 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 --git a/fs/dquot.c b/fs/dquot.c
index de9a29f..2809768 100644 (file)
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -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(struct dquot *dquot, qsize_t number)
        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(struct dquot *dquot)
        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 *dquot, const char warntype)
        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 +891,93 @@ static void print_warning(struct dquot *dquot, const char warntype)
 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 atomic_t seq;
+       struct sk_buff *skb;
+       void *msg_head;
+       int ret;
+
+       /* We have to allocate using GFP_NOFS as we are called from a
+        * filesystem performing write and thus further recursion into
+        * the fs to free some data could cause deadlocks. */
+       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, atomic_add_return(1, &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 +991,14 @@ static inline char ignore_hardlimit(struct dquot *dquot)
 /* 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 +1006,14 @@ static int check_idq(struct dquot *dquot, ulong inodes, char *warntype)
           (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 +1023,7 @@ static int check_idq(struct dquot *dquot, ulong inodes, char *warntype)
 /* 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 +1031,7 @@ static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *war
           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 +1040,7 @@ static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *war
            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 +1048,7 @@ static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *war
           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 +1143,7 @@ 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 +1189,7 @@ int dquot_alloc_inode(const struct inode *inode, unsigned long number)
        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 +1311,7 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
        /* 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 +1885,7 @@ 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 +1894,7 @@ static ctl_table fs_dqstats_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
+#endif
        { .ctl_name = 0 },
 };
 
@@ -1877,6 +1956,11 @@ 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 --git a/include/linux/quota.h b/include/linux/quota.h
index 6243982..6e0393a 100644 (file)
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -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>