lkml.org 
[lkml]   [2005]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] Use of getblk differs between locations
From
Date
On Mon, 2005-10-10 at 18:07 -0700, Andrew Morton wrote:
> Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> wrote:
> >
> > On Mon, 10 Oct 2005, Andrew Morton wrote:
> >
> > > Anton Altaparmakov <aia21@cam.ac.uk> wrote:
> > >>
> > >> > Maybe the best solution is neither one nor another. Testing and failing
> > >> > gracefully seems better.
> > >> >
> > >> > What do you think?
> > >>
> > >> I certainly agree with you there. I neither want a deadlock nor
> > >> corruption. (-:
> > >
> > > Yup. In the present implementation __getblk_slow() "cannot fail". It's
> > > conceivable that at some future stage we'll change __getblk_slow() so that
> > > it returns NULL on an out-of-memory condition.
> >
> > The question is if it is desired --- it will make bread return NULL on
> > out-of-memory condition, callers will treat it like an IO error, skipping
> > access to the affected block, causing damage on perfectly healthy
> > filesystem.
>
> Yes, that is a bit dumb. A filesystem might indeed want to take different
> action for ENOMEM versus EIO.
>
> > I liked what linux-2.0 did in this case --- if the kernel was out of
> > memory, getblk just took another buffer, wrote it if it was dirty and used
> > it. Except for writeable loopback device (where writing one buffer
> > generates more dirty buffers), it couldn't deadlock.
>
> Wouldn't it be better if bread() were to return ERR_PTR(-EIO) or
> ERR_PTR(-ENOMEM)? Big change.

It would indeed. Much better. And whilst at it, it would be even
better if we had a lot more error codes like "ERR_PTR(-EDEVUNPLUGGED)"
for example... But that would be an even better change. Anyone feeling
like touching every block driver in the kernel? (-;

Best regards,

Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-10-11 10:04    [W:0.044 / U:18.504 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site