Retain readahead of underlying device.

(If libdevmapper version supports it).

git-svn-id: https://cryptsetup.googlecode.com/svn/trunk@54 36d66b0a-2a48-0410-832c-cd162a569da5

diff --git a/lib/libdevmapper.c b/lib/libdevmapper.c
index 3e74029..3859508 100644 (file)
--- a/lib/libdevmapper.c
+++ b/lib/libdevmapper.c
@@ -6,10 +6,13 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
+#include <sys/ioctl.h>
 #include <unistd.h>
 #include <dirent.h>
 #include <errno.h>
 #include <libdevmapper.h>
+#include <fcntl.h>
+#include <linux/fs.h>
 
 #include "libcryptsetup.h"
 #include "internal.h"
@@ -111,6 +114,23 @@ static char *lookup_dev(const char *dev)
        return __lookup_dev(buf, makedev(major, minor));
 }
 
+static int _dev_read_ahead(const char *dev, uint32_t *read_ahead)
+{
+       int fd, r = 0;
+       long read_ahead_long;
+
+       if ((fd = open(dev, O_RDONLY)) < 0)
+               return 0;
+
+       r = ioctl(fd, BLKRAGET, &read_ahead_long) ? 0 : 1;
+       close(fd);
+
+       if (r)
+               *read_ahead = (uint32_t) read_ahead_long;
+
+       return r;
+}
+
 static char *get_params(struct crypt_options *options, const char *key)
 {
        char *params;
@@ -235,6 +255,7 @@ static int dm_create_device(int reload, struct crypt_options *options,
        char *params = NULL;
        char *error = NULL;
        int r = -EINVAL;
+       uint32_t read_ahead = 0;
 
        params = get_params(options, key);
        if (!params)
@@ -248,6 +269,12 @@ static int dm_create_device(int reload, struct crypt_options *options,
                 goto out;
        if (!dm_task_add_target(dmt, 0, options->size, CRYPT_TARGET, params))
                goto out;
+
+#ifdef DM_READ_AHEAD_MINIMUM_FLAG
+       if (_dev_read_ahead(options->device, &read_ahead) &&
+           !dm_task_set_read_ahead(dmt, read_ahead, DM_READ_AHEAD_MINIMUM_FLAG))
+               goto out;
+#endif
        if (!dm_task_run(dmt))
                goto out;