Re: [PATCH 3/6] direct-io: do not merge logically non-contiguous requests

From: Mike Fedyk
Date: Fri May 21 2010 - 21:47:44 EST

On Fri, May 21, 2010 at 10:03 AM, Josef Bacik <josef@xxxxxxxxxx> wrote:
> Btrfs cannot handle having logically non-contiguous requests submitted. ÂFor
> example if you have
> Logical: Â[0-4095][HOLE][8192-12287]
> Physical: [0-4095] Â Â Â[4096-8191]
> Normally the DIO code would put these into the same BIO's. ÂThe problem is we
> need to know exactly what offset is associated with what BIO so we can do our
> checksumming and unlocking properly, so putting them in the same BIO doesn't
> work. ÂSo add another check where we submit the current BIO if the physical
> blocks are not contigous OR the logical blocks are not contiguous.
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> V1->V2
> -Be more verbose in the in-code comment
> Âfs/direct-io.c | Â 20 ++++++++++++++++++--
> Â1 files changed, 18 insertions(+), 2 deletions(-)

Btrfs has been pretty much self-contained (working well compiled
against 2.6.32 for example). Is there a way that this wouldn't just
start silently breaking for people compiling the latest btrfs with
dkms against older kernels?
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