Messages in this thread | | | Subject | Re: [PATCH] Use of getblk differs between locations | From | Anton Altaparmakov <> | Date | Tue, 11 Oct 2005 09:01:19 +0100 |
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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/
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