Merge pull request #1151 from giuseppe/read-proc-file-using-page

minor cleanups to read_file

Author: flouthoc

src/libcrun/utils.c

@@ -707,6 +707,19 @@ check_running_in_user_namespace (libcrun_error_t *err)
   return ret;
 }
 
+static size_t
+get_page_size ()
+{
+  static atomic_long cached_pagesize = 0;
+  atomic_long pagesize = cached_pagesize;
+  if (pagesize == 0)
+    {
+      pagesize = (long) sysconf (_SC_PAGESIZE);
+      cached_pagesize = pagesize;
+    }
+  return (size_t) pagesize;
+}
+
 static int selinux_enabled = -1;
 static int apparmor_enabled = -1;
 
@@ -725,7 +738,7 @@ libcrun_initialize_selinux (libcrun_error_t *err)
   if (UNLIKELY (fd < 0))
     return crun_make_error (err, errno, "open /proc/mounts");
 
-  ret = read_all_fd (fd, "/proc/mounts", &out, &len, err);
+  ret = read_all_fd_with_size_hint (fd, "/proc/mounts", &out, &len, get_page_size (), err);
   if (UNLIKELY (ret < 0))
     return ret;
 
@@ -866,21 +879,26 @@ set_apparmor_profile (const char *profile, bool now, libcrun_error_t *err)
 }
 
 int
-read_all_fd (int fd, const char *description, char **out, size_t *len, libcrun_error_t *err)
+read_all_fd_with_size_hint (int fd, const char *description, char **out, size_t *len, size_t size_hint, libcrun_error_t *err)
 {
-  int ret;
+  cleanup_free char *buf = NULL;
   size_t nread, allocated;
+  size_t pagesize = 0;
   off_t size = 0;
-  cleanup_free char *buf = NULL;
+  int ret;
 
-  ret = get_file_size (fd, &size);
-  if (UNLIKELY (ret < 0))
-    return crun_make_error (err, errno, "error stat'ing file `%s`", description);
+  if (size_hint)
+    allocated = size_hint;
+  else
+    {
+      ret = get_file_size (fd, &size);
+      if (UNLIKELY (ret < 0))
+        return crun_make_error (err, errno, "error stat'ing file `%s`", description);
+
+      allocated = size == 0 ? 1023 : size;
+    }
 
   /* NUL terminate the buffer.  */
-  allocated = size + 1;
-  if (size == 0)
-    allocated = 1023;
   buf = xmalloc (allocated + 1);
   nread = 0;
   while ((size && nread < (size_t) size) || size == 0)
@@ -896,7 +914,14 @@ read_all_fd (int fd, const char *description, char **out, size_t *len, libcrun_e
 
       if (nread == allocated)
         {
-          allocated += 4096;
+          if (size)
+            break;
+
+          if (pagesize == 0)
+            pagesize = get_page_size ();
+
+          allocated += pagesize;
+
           buf = xrealloc (buf, allocated + 1);
         }
     }
@@ -1160,15 +1185,14 @@ copy_from_fd_to_fd (int src, int dst, int consume, libcrun_error_t *err)
 {
   int ret;
   ssize_t nread;
+  size_t pagesize = get_page_size ();
   do
     {
       cleanup_free char *buffer = NULL;
       ssize_t remaining;
 
-#define BUFFER_SIZE 4096
-
 #ifdef HAVE_COPY_FILE_RANGE
-      nread = copy_file_range (src, NULL, dst, NULL, BUFFER_SIZE, 0);
+      nread = copy_file_range (src, NULL, dst, NULL, pagesize, 0);
       if (nread < 0 && (errno == EINVAL || errno == EXDEV))
         goto fallback;
       if (consume && nread < 0 && errno == EAGAIN)
@@ -1182,8 +1206,8 @@ copy_from_fd_to_fd (int src, int dst, int consume, libcrun_error_t *err)
     fallback:
 #endif
 
-      buffer = xmalloc (BUFFER_SIZE);
-      nread = TEMP_FAILURE_RETRY (read (src, buffer, BUFFER_SIZE));
+      buffer = xmalloc (pagesize);
+      nread = TEMP_FAILURE_RETRY (read (src, buffer, pagesize));
       if (consume && nread < 0 && errno == EAGAIN)
         return 0;
       if (nread < 0 && errno == EIO)

src/libcrun/utils.h

@@ -295,7 +295,13 @@ int add_selinux_mount_label (char **ret, const char *data, const char *label, co
 
 int set_apparmor_profile (const char *profile, bool now, libcrun_error_t *err);
 
-int read_all_fd (int fd, const char *description, char **out, size_t *len, libcrun_error_t *err);
+int read_all_fd_with_size_hint (int fd, const char *description, char **out, size_t *len, size_t hint, libcrun_error_t *err);
+
+static inline int
+read_all_fd (int fd, const char *description, char **out, size_t *len, libcrun_error_t *err)
+{
+  return read_all_fd_with_size_hint (fd, description, out, len, 0, err);
+}
 
 int read_all_file (const char *path, char **out, size_t *len, libcrun_error_t *err);