[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>

1 files changed, 150 insertions, 10 deletions

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);