nmeter: 4k buffers are too small for /proc files,

 make them dynamically sized with 16k upper limit. +75 bytes

1 files changed, 30 insertions, 15 deletions

diff --git a/procps/nmeter.c b/procps/nmeter.c
index cded67e56..068c739fb 100644
--- a/procps/nmeter.c
+++ b/procps/nmeter.c
@@ -22,11 +22,14 @@
 
 typedef unsigned long long ullong;
 
-enum { PROC_FILE_SIZE = 4096 };
+enum {  /* Preferably use powers of 2 */
+        PROC_MIN_FILE_SIZE = 256,
+        PROC_MAX_FILE_SIZE = 16 * 1024,
+};
 
 typedef struct proc_file {
         char *file;
-        //const char *name;
+        int file_sz;
         smallint last_gen;
 } proc_file;
 
@@ -124,30 +127,42 @@ static void put_question_marks(int count)
                 put_c('?');
 }
 
-static void readfile_z(char *buf, int sz, const char* fname)
+static void readfile_z(proc_file *pf, const char* fname)
 {
 // open_read_close() will do two reads in order to be sure we are at EOF,
 // and we don't need/want that.
-//      sz = open_read_close(fname, buf, sz-1);
-
-        int fd = xopen(fname, O_RDONLY);
+        int fd;
+        int sz, rdsz;
+        char *buf;
+
+        sz = pf->file_sz;
+        buf = pf->file;
+        if (!buf) {
+                buf = xmalloc(PROC_MIN_FILE_SIZE);
+                sz = PROC_MIN_FILE_SIZE;
+        }
+ again:
+        fd = xopen(fname, O_RDONLY);
         buf[0] = '\0';
-        sz = read(fd, buf, sz - 1);
-        if (sz > 0)
-                buf[sz] = '\0';
+        rdsz = read(fd, buf, sz-1);
         close(fd);
+        if (rdsz > 0) {
+                if (rdsz == sz-1 && sz < PROC_MAX_FILE_SIZE) {
+                        sz *= 2;
+                        buf = xrealloc(buf, sz);
+                        goto again;
+                }
+                buf[rdsz] = '\0';
+        }
+        pf->file_sz = sz;
+        pf->file = buf;
 }
 
 static const char* get_file(proc_file *pf)
 {
         if (pf->last_gen != gen) {
                 pf->last_gen = gen;
-                // We allocate PROC_FILE_SIZE bytes. This wastes memory,
-                // but allows us to allocate only once (at first sample)
-                // per proc file, and reuse buffer for each sample
-                if (!pf->file)
-                        pf->file = xmalloc(PROC_FILE_SIZE);
-                readfile_z(pf->file, PROC_FILE_SIZE, proc_name[pf - &first_proc_file]);
+                readfile_z(pf, proc_name[pf - &first_proc_file]);
         }
         return pf->file;
 }