Messages in this thread | | | Date | Thu, 16 Oct 2014 18:01:26 -0400 | From | Matthew Wilcox <> | Subject | Re: [PATCH v11 19/21] dax: Add dax_zero_page_range |
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On Thu, Oct 16, 2014 at 02:38:24PM +0200, Mathieu Desnoyers wrote: > > +int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, > > nit: unsigned -> unsigned int ? > > Do we want a unsigned int or unsigned long here ?
It's supposed to be for a fragment of a page, so until we see a machine with PAGE_SIZE > 4GB, we're good to use an unsigned int.
> > if (!length) > > return 0; > > + BUG_ON((offset + length) > PAGE_CACHE_SIZE); > > Isn't it a bit extreme to BUG_ON this condition ? We could return an > error to the caller, and perhaps WARN_ON_ONCE(), but BUG_ON() appears to > be slightly too strong here.
Dave Chinner asked for it :-) The filesystem is supposed to be doing this clamping (until the last version, I had this function doing the clamping, and I was told off for "leaving landmines lying around".
> > +static inline int dax_zero_page_range(struct inode *i, loff_t frm, > > + unsigned len, get_block_t gb) > > +{ > > + return 0; > > Should we return 0 or -ENOSYS here ?
I kind of wonder if we shouldn't just declare the function. It's called like this:
if (IS_DAX(inode)) return dax_zero_page_range(inode, from, length, ext4_get_block); return __ext4_block_zero_page_range(handle, mapping, from, length);
and if CONFIG_DAX is not set, IS_DAX evaluates to 0 at compile time, so the compiler will optimise out the call to dax_zero_page_range() anyway.
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