Bug 865387 - Handle the read-ahead flag operation on Linux. r=Yoric

dom/system/OSFileConstants.cpp

@@ -15,6 +15,10 @@
 #include "sys/stat.h"
 #endif // defined(XP_UNIX)
 
+#if defined(XP_LINUX)
+#include <linux/fadvise.h>
+#endif // defined(XP_LINUX)
+
 #if defined(XP_MACOSX)
 #include "copyfile.h"
 #endif // defined(XP_MACOSX)
@@ -320,6 +324,10 @@ static const dom::ConstantSpec gLibcProperties[] =
   INT_CONSTANT(AT_SYMLINK_NOFOLLOW),
 #endif //defined(AT_SYMLINK_NOFOLLOW)
 
+#if defined(POSIX_FADV_SEQUENTIAL)
+  INT_CONSTANT(POSIX_FADV_SEQUENTIAL),
+#endif //defined(POSIX_FADV_SEQUENTIAL)
+
   // access
 #if defined(F_OK)
   INT_CONSTANT(F_OK),

toolkit/components/osfile/modules/osfile_unix_back.jsm

@@ -447,6 +447,14 @@
                     /*buf*/   Types.void_t.out_ptr,
                     /*nbytes*/Types.size_t);
 
+       UnixFile.posix_fadvise =
+         declareFFI("posix_fadvise", ctypes.default_abi,
+                    /*return*/ Types.int,
+                    /*fd*/     Types.fd,
+                    /*offset*/ Types.off_t,
+                    /*len*/    Types.off_t,
+                    /*advise*/ Types.int);
+
        if (OS.Constants.libc._DARWIN_FEATURE_64_BIT_INODE) {
          // Special case for MacOS X 10.5+
          // Symbol name "readdir" still exists but is used for a

toolkit/components/osfile/modules/osfile_unix_front.jsm

@@ -92,6 +92,13 @@
       * @throws {OS.File.Error} In case of I/O error.
       */
      File.prototype._read = function _read(buffer, nbytes, options) {
+      // Populate the page cache with data from a file so the subsequent reads
+      // from that file will not block on disk I/O.
+       if ((UnixFile.posix_fadvise &&
+            options.sequential || !("sequential" in options))) {
+         UnixFile.posix_fadvise(this.fd, 0, nbytes,
+          OS.Constants.libc.POSIX_FADV_SEQUENTIAL);
+       }
        return throw_on_negative("read",
          UnixFile.read(this.fd, buffer, nbytes)
        );