[PATCH] convert /proc/devices to use seq_file interface

A Christoph suggested that the /proc/devices file be converted to use the
seq_file interface.  This patch does that.

I've obxerved one or two installation that had sufficiently large sans that
they overran the 4k limit on /proc/devices.

Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 320 insertions, 53 deletions

diff --git a/block/genhd.c b/block/genhd.c
index f1ed83f3f083..db57546a709d 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -38,34 +38,100 @@ static inline int major_to_index(int major)
         return major % MAX_PROBE_HASH;
 }
 
-#ifdef CONFIG_PROC_FS
-/* get block device names in somewhat random order */
-int get_blkdev_list(char *p, int used)
+struct blkdev_info {
+        int index;
+        struct blk_major_name *bd;
+};
+
+/*
+ * iterate over a list of blkdev_info structures.  allows
+ * the major_names array to be iterated over from outside this file
+ * must be called with the block_subsys_sem held
+ */
+void *get_next_blkdev(void *dev)
+{
+        struct blkdev_info *info;
+
+        if (dev == NULL) {
+                info = kmalloc(sizeof(*info), GFP_KERNEL);
+                if (!info)
+                        goto out;
+                info->index=0;
+                info->bd = major_names[info->index];
+                if (info->bd)
+                        goto out;
+        } else {
+                info = dev;
+        }
+
+        while (info->index < ARRAY_SIZE(major_names)) {
+                if (info->bd)
+                        info->bd = info->bd->next;
+                if (info->bd)
+                        goto out;
+                /*
+                 * No devices on this chain, move to the next
+                 */
+                info->index++;
+                info->bd = (info->index < ARRAY_SIZE(major_names)) ?
+                        major_names[info->index] : NULL;
+                if (info->bd)
+                        goto out;
+        }
+
+out:
+        return info;
+}
+
+void *acquire_blkdev_list(void)
+{
+        down(&block_subsys_sem);
+        return get_next_blkdev(NULL);
+}
+
+void release_blkdev_list(void *dev)
+{
+        up(&block_subsys_sem);
+        kfree(dev);
+}
+
+
+/*
+ * Count the number of records in the blkdev_list.
+ * must be called with the block_subsys_sem held
+ */
+int count_blkdev_list(void)
 {
         struct blk_major_name *n;
-        int i, len;
+        int i, count;
 
-        len = snprintf(p, (PAGE_SIZE-used), "\nBlock devices:\n");
+        count = 0;
 
-        down(&block_subsys_sem);
         for (i = 0; i < ARRAY_SIZE(major_names); i++) {
-                for (n = major_names[i]; n; n = n->next) {
-                        /*
-                         * If the curent string plus the 5 extra characters
-                         * in the line would run us off the page, then we're done
-                         */
-                        if ((len + used + strlen(n->name) + 5) >= PAGE_SIZE)
-                                goto page_full;
-                        len += sprintf(p+len, "%3d %s\n",
-                                       n->major, n->name);
-                }
+                for (n = major_names[i]; n; n = n->next)
+                                count++;
         }
-page_full:
-        up(&block_subsys_sem);
 
-        return len;
+        return count;
 }
-#endif
+
+/*
+ * extract the major and name values from a blkdev_info struct
+ * passed in as a void to *dev.  Must be called with
+ * block_subsys_sem held
+ */
+int get_blkdev_info(void *dev, int *major, char **name)
+{
+        struct blkdev_info *info = dev;
+
+        if (info->bd == NULL)
+                return 1;
+
+        *major = info->bd->major;
+        *name = info->bd->name;
+        return 0;
+}
+
 
 int register_blkdev(unsigned int major, const char *name)
 {
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 3b1b1eefdbb0..21195c481637 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -35,7 +35,7 @@ static struct char_device_struct {
         unsigned int major;
         unsigned int baseminor;
         int minorct;
-        const char *name;
+        char name[64];
         struct file_operations *fops;
         struct cdev *cdev;              /* will die */
 } *chrdevs[MAX_PROBE_HASH];
@@ -46,34 +46,84 @@ static inline int major_to_index(int major)
         return major % MAX_PROBE_HASH;
 }
 
-/* get char device names in somewhat random order */
-int get_chrdev_list(char *page)
-{
+struct chrdev_info {
+        int index;
         struct char_device_struct *cd;
-        int i, len;
+};
 
-        len = sprintf(page, "Character devices:\n");
+void *get_next_chrdev(void *dev)
+{
+        struct chrdev_info *info;
 
+        if (dev == NULL) {
+                info = kmalloc(sizeof(*info), GFP_KERNEL);
+                if (!info)
+                        goto out;
+                info->index=0;
+                info->cd = chrdevs[info->index];
+                if (info->cd)
+                        goto out;
+        } else {
+                info = dev;
+        }
+
+        while (info->index < ARRAY_SIZE(chrdevs)) {
+                if (info->cd)
+                        info->cd = info->cd->next;
+                if (info->cd)
+                        goto out;
+                /*
+                 * No devices on this chain, move to the next
+                 */
+                info->index++;
+                info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
+                        chrdevs[info->index] : NULL;
+                if (info->cd)
+                        goto out;
+        }
+
+out:
+        return info;
+}
+
+void *acquire_chrdev_list(void)
+{
         down(&chrdevs_lock);
+        return get_next_chrdev(NULL);
+}
+
+void release_chrdev_list(void *dev)
+{
+        up(&chrdevs_lock);
+        kfree(dev);
+}
+
+
+int count_chrdev_list(void)
+{
+        struct char_device_struct *cd;
+        int i, count;
+
+        count = 0;
+
         for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
-                for (cd = chrdevs[i]; cd; cd = cd->next) {
-                        /*
-                         * if the current name, plus the 5 extra characters
-                         * in the device line for this entry
-                         * would run us off the page, we're done
-                         */
-                        if ((len+strlen(cd->name) + 5) >= PAGE_SIZE)
-                                goto page_full;
-
-
-                        len += sprintf(page+len, "%3d %s\n",
-                                       cd->major, cd->name);
-                }
+                for (cd = chrdevs[i]; cd; cd = cd->next)
+                        count++;
         }
-page_full:
-        up(&chrdevs_lock);
 
-        return len;
+        return count;
+}
+
+int get_chrdev_info(void *dev, int *major, char **name)
+{
+        struct chrdev_info *info = dev;
+
+        if (info->cd == NULL)
+                return 1;
+
+        *major = info->cd->major;
+        *name = info->cd->name;
+        return 0;
 }
 
 /*
@@ -121,7 +171,7 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
         cd->major = major;
         cd->baseminor = baseminor;
         cd->minorct = minorct;
-        cd->name = name;
+        strncpy(cd->name,name, 64);
 
         i = major_to_index(major);
 
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 63bf6c00fa0c..8f8014285a34 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -20,6 +20,7 @@
 #include <linux/time.h>
 #include <linux/kernel.h>
 #include <linux/kernel_stat.h>
+#include <linux/fs.h>
 #include <linux/tty.h>
 #include <linux/string.h>
 #include <linux/mman.h>
@@ -62,7 +63,6 @@
  */
 extern int get_hardware_list(char *);
 extern int get_stram_list(char *);
-extern int get_chrdev_list(char *);
 extern int get_filesystem_list(char *);
 extern int get_exec_domain_list(char *);
 extern int get_dma_list(char *);
@@ -248,6 +248,154 @@ static int cpuinfo_open(struct inode *inode, struct file *file)
 {
         return seq_open(file, &cpuinfo_op);
 }
+
+enum devinfo_states {
+        CHR_HDR,
+        CHR_LIST,
+        BLK_HDR,
+        BLK_LIST,
+        DEVINFO_DONE
+};
+
+struct devinfo_state {
+        void *chrdev;
+        void *blkdev;
+        unsigned int num_records;
+        unsigned int cur_record;
+        enum devinfo_states state;
+};
+
+static void *devinfo_start(struct seq_file *f, loff_t *pos)
+{
+        struct devinfo_state *info = f->private;
+
+        if (*pos) {
+                if ((info) && (*pos <= info->num_records))
+                        return info;
+                return NULL;
+        }
+        info = kmalloc(sizeof(*info), GFP_KERNEL);
+        f->private = info;
+        info->chrdev = acquire_chrdev_list();
+        info->blkdev = acquire_blkdev_list();
+        info->state = CHR_HDR;
+        info->num_records = count_chrdev_list();
+        info->num_records += count_blkdev_list();
+        info->num_records += 2; /* Character and Block headers */
+        *pos = 1;
+        info->cur_record = *pos;
+        return info;
+}
+
+static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos)
+{
+        int idummy;
+        char *ndummy;
+        struct devinfo_state *info = f->private;
+
+        switch (info->state) {
+                case CHR_HDR:
+                        info->state = CHR_LIST;
+                        (*pos)++;
+                        /*fallthrough*/
+                case CHR_LIST:
+                        if (get_chrdev_info(info->chrdev,&idummy,&ndummy)) {
+                                /*
+                                 * The character dev list is complete
+                                 */
+                                info->state = BLK_HDR;
+                        } else {
+                                info->chrdev = get_next_chrdev(info->chrdev);
+                        }
+                        (*pos)++;
+                        break;
+                case BLK_HDR:
+                        info->state = BLK_LIST;
+                        (*pos)++;
+                        break;
+                case BLK_LIST:
+                        if (get_blkdev_info(info->blkdev,&idummy,&ndummy)) {
+                                /*
+                                 * The block dev list is complete
+                                 */
+                                info->state = DEVINFO_DONE;
+                        } else {
+                                info->blkdev = get_next_blkdev(info->blkdev);
+                        }
+                        (*pos)++;
+                        break;
+                case DEVINFO_DONE:
+                        (*pos)++;
+                        info->cur_record = *pos;
+                        info = NULL;
+                        break;
+                default:
+                        break;
+        }
+        if (info)
+                info->cur_record = *pos;
+        return info;
+}
+
+static void devinfo_stop(struct seq_file *f, void *v)
+{
+        struct devinfo_state *info = f->private;
+
+        if (info) {
+                release_chrdev_list(info->chrdev);
+                release_blkdev_list(info->blkdev);
+                f->private = NULL;
+                kfree(info);
+        }
+}
+
+static int devinfo_show(struct seq_file *f, void *arg)
+{
+        int major;
+        char *name;
+        struct devinfo_state *info = f->private;
+
+        switch(info->state) {
+                case CHR_HDR:
+                        seq_printf(f,"Character devices:\n");
+                        /* fallthrough */
+                case CHR_LIST:
+                        if (!get_chrdev_info(info->chrdev,&major,&name))
+                                seq_printf(f,"%3d %s\n",major,name);
+                        break;
+                case BLK_HDR:
+                        seq_printf(f,"\nBlock devices:\n");
+                        /* fallthrough */
+                case BLK_LIST:
+                        if (!get_blkdev_info(info->blkdev,&major,&name))
+                                seq_printf(f,"%3d %s\n",major,name);
+                        break;
+                default:
+                        break;
+        }
+
+        return 0;
+}
+
+static  struct seq_operations devinfo_op = {
+        .start  = devinfo_start,
+        .next   = devinfo_next,
+        .stop   = devinfo_stop,
+        .show   = devinfo_show,
+};
+
+static int devinfo_open(struct inode *inode, struct file *file)
+{
+        return seq_open(file, &devinfo_op);
+}
+
+static struct file_operations proc_devinfo_operations = {
+        .open           = devinfo_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
 static struct file_operations proc_cpuinfo_operations = {
         .open           = cpuinfo_open,
         .read           = seq_read,
@@ -450,14 +598,6 @@ static struct file_operations proc_stat_operations = {
         .release        = single_release,
 };
 
-static int devices_read_proc(char *page, char **start, off_t off,
-                                 int count, int *eof, void *data)
-{
-        int len = get_chrdev_list(page);
-        len += get_blkdev_list(page+len, len);
-        return proc_calc_metrics(page, start, off, count, eof, len);
-}
-
 /*
  * /proc/interrupts
  */
@@ -582,7 +722,6 @@ void __init proc_misc_init(void)
 #ifdef CONFIG_STRAM_PROC
                 {"stram",       stram_read_proc},
 #endif
-                {"devices",     devices_read_proc},
                 {"filesystems", filesystems_read_proc},
                 {"cmdline",     cmdline_read_proc},
                 {"locks",       locks_read_proc},
@@ -598,6 +737,7 @@ void __init proc_misc_init(void)
         entry = create_proc_entry("kmsg", S_IRUSR, &proc_root);
         if (entry)
                 entry->proc_fops = &proc_kmsg_operations;
+        create_seq_entry("devices", 0, &proc_devinfo_operations);
         create_seq_entry("cpuinfo", 0, &proc_cpuinfo_operations);
         create_seq_entry("partitions", 0, &proc_partitions_operations);
         create_seq_entry("stat", 0, &proc_stat_operations);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d1e370d25f7b..552cedfa6064 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1383,6 +1383,12 @@ extern int register_chrdev(unsigned int, const char *,
 extern int unregister_chrdev(unsigned int, const char *);
 extern void unregister_chrdev_region(dev_t, unsigned);
 extern int chrdev_open(struct inode *, struct file *);
+extern int get_chrdev_list(char *);
+extern void *acquire_chrdev_list(void);
+extern int count_chrdev_list(void);
+extern void *get_next_chrdev(void *);
+extern int get_chrdev_info(void *, int *, char **);
+extern void release_chrdev_list(void *);
 
 /* fs/block_dev.c */
 #define BDEVNAME_SIZE   32      /* Largest string for a blockdev identifier */
@@ -1391,6 +1397,11 @@ extern const char *bdevname(struct block_device *bdev, char *buffer);
 extern struct block_device *lookup_bdev(const char *);
 extern struct block_device *open_bdev_excl(const char *, int, void *);
 extern void close_bdev_excl(struct block_device *);
+extern void *acquire_blkdev_list(void);
+extern int count_blkdev_list(void);
+extern void *get_next_blkdev(void *);
+extern int get_blkdev_info(void *, int *, char **);
+extern void release_blkdev_list(void *);
 
 extern void init_special_inode(struct inode *, umode_t, dev_t);