[PATCH 0/1] LP#444915: readahead not merging in the elevator

Andy Whitcroft apw at canonical.com
Tue Oct 13 11:18:38 UTC 2009

We have reports of slow mounting of FAT filesystems on external drives.
This turns out to be a bug in the new fastfail code in the elevator which
completely prevents merging of any readahead requests.  As all of the
FAT reads are pre-readahead to fix this very performance problem they
all were submitted to the device as single 512 transactions.  Fail.

This patch implements the painfully obvious fix for the issue.

Thanks to Stefan Bader for keeping me sane during the extended debug.

For Karmic.


Andy Whitcroft (1):
  UBUNTU: [Upstream] elevator: fix fastfail checks to allow merge of
    readahead requests

 block/elevator.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

More information about the kernel-team mailing list