block size check in __getblk_slow
piyush moghe
pmkernel at gmail.com
Fri Jul 1 02:45:26 EDT 2011
Thanks Jonathan for your inputs.
Since I am new to Linux Kernel Development I am learning the process of
patch posting and development, once I will
be done with that I will post the patch for review.
Regards,
Piyush
On Thu, Jun 30, 2011 at 1:13 AM, Jonathan Neuschäfer
<j.neuschaefer at gmx.net>wrote:
> On Mon, Jun 27, 2011 at 02:23:24PM +0530, piyush moghe wrote:
> > Hi All,
> >
> > I am new to linux kernel code and interested in filesystems and block
> I/O.
> >
> > While going through the block read code ( in __bread function ) I found
> that
> > when we try to read the block ( __getblk ) we first check for the block
> > buffer page in page cache ( using __find_get_block function ) and if not
> we
> > do a slow path ( using __getblk_slow function which checks page in cache
> > again and if not found again then allocate a buffer page in cache ).
> >
> > Now my problem is, as part of __getblk_slow we compare block size with
> bdev
> > logical block size and also check that block size should not be less than
> > 512 and not greater than PAGE_SIZE ( 4K, for PAGE_SHIFT set to 13 )
> > although these all checks can be moved to upper level function i.e
> __getblk
> > and that too before calling __find_get_block ( to find block in page
> cache )
> > so as to avoid looking for block in page cache if the size is invalid.
> Sounds reasonable.
>
> >
> > Please let me know your comments on this.
>
> I think this is advanced enough to be discussed on the LKML, just send
> an RFC (request for comments) patch and someone should comment. But
> LKML can be a bit harsh if you're not used to it.
>
> If you want to discuss it here, you might also want to send a patch
> in addition to your thoughts, it's just a lot easier to get the context
> and the exact thing you're trying to do from a patch than from mere
> words.
>
> HTH,
> Jonathan Neuschäfer
>
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