proc: revert /proc/uptime to ->read_proc hook

Turned out some VMware userspace does pread(2) on /proc/uptime, but
seqfiles currently don't allow pread() resulting in -ESPIPE.

Seqfiles in theory can do pread(), but this can be a long story,
so revert to ->read_proc until then.

http://bugzilla.kernel.org/show_bug.cgi?id=11856

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

1 files changed, 20 insertions, 18 deletions

diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
index 0c10a0b3f146..df26aa88fa47 100644
--- a/fs/proc/uptime.c
+++ b/fs/proc/uptime.c
@@ -1,43 +1,45 @@
-#include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/proc_fs.h>
 #include <linux/sched.h>
-#include <linux/seq_file.h>
 #include <linux/time.h>
 #include <asm/cputime.h>
 
-static int uptime_proc_show(struct seq_file *m, void *v)
+static int proc_calc_metrics(char *page, char **start, off_t off,
+                                 int count, int *eof, int len)
+{
+        if (len <= off + count)
+                *eof = 1;
+        *start = page + off;
+        len -= off;
+        if (len > count)
+                len = count;
+        if (len < 0)
+                len = 0;
+        return len;
+}
+
+static int uptime_read_proc(char *page, char **start, off_t off, int count,
+                            int *eof, void *data)
 {
         struct timespec uptime;
         struct timespec idle;
+        int len;
         cputime_t idletime = cputime_add(init_task.utime, init_task.stime);
 
         do_posix_clock_monotonic_gettime(&uptime);
         monotonic_to_bootbased(&uptime);
         cputime_to_timespec(idletime, &idle);
-        seq_printf(m, "%lu.%02lu %lu.%02lu\n",
+        len = sprintf(page, "%lu.%02lu %lu.%02lu\n",
                         (unsigned long) uptime.tv_sec,
                         (uptime.tv_nsec / (NSEC_PER_SEC / 100)),
                         (unsigned long) idle.tv_sec,
                         (idle.tv_nsec / (NSEC_PER_SEC / 100)));
-        return 0;
+        return proc_calc_metrics(page, start, off, count, eof, len);
 }
 
-static int uptime_proc_open(struct inode *inode, struct file *file)
-{
-        return single_open(file, uptime_proc_show, NULL);
-}
-
-static const struct file_operations uptime_proc_fops = {
-        .open           = uptime_proc_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = single_release,
-};
-
 static int __init proc_uptime_init(void)
 {
-        proc_create("uptime", 0, NULL, &uptime_proc_fops);
+        create_proc_read_entry("uptime", 0, NULL, uptime_read_proc, NULL);
         return 0;
 }
 module_init(proc_uptime_init);