This option has never worked. If you try setting the block size on a
block device, and then read it using --getbsz, you will see that the
block size never changes.
The reason for this is because the block size is specific to the
current file descriptor opening the block device, so the change of
block size only persists for as long as blockdev has the device open,
and is lost once blockdev exits.
Also the block size is not really used anywhere. Filesystems, for
example, have their own idea of block size and ignore this setting
completely.
(Thanks Masayoshi Mizuma for diagnosing the problem)
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Use dates without the day, use the full month name, put "util-linux" in
the lower left corner, and "User Commands" or "System Administration"
at the top center.
Also improve here and there the one-line program description.
Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
In Linux 2.6 the BLKRASET ioctl has the desired effect for mounted
file-systems. In Linux 2.4 it appears to set the number of blocks to
read-ahead on the *device* as opposed to within a *file*, and the
maximum value of this number is 255. As a result the invocation of
blockdev will fail on Linux 2.4 for any usefully large value of
READAHEAD, and will not in any case have the desired affect for
fragmented files.
(Based on the blockdev-getfra-setfra.patch Debian patch.)
Signed-off-by: Karel Zak <kzak@redhat.com>
Richard W.M. Jones
Benno Schulenberg
Davidlohr Bueso
Karel Zak
Peter Breitenlohner
Li Zefan