Re: [PATCH 0/7] RFC: high-order folio support for I/O

[Hannes Reinecke <hare@suse.de>]

On 6/14/23 17:06, Hannes Reinecke wrote:
[ .. ]
> 
> Whee! That works!
> 
> Rebased things with your memcpy_{to,from}_folio() patches, disabled that 
> chunk, and:
> 
> # mount /dev/ram0 /mnt
> XFS (ram0): Mounting V5 Filesystem 5cd71ab5-2d11-4c18-97dd-71708f40e551
> XFS (ram0): Ending clean mount
> xfs filesystem being mounted at /mnt supports timestamps until 
> 2038-01-19 (0x7fffffff)
> # umount /mnt
> XFS (ram0): Unmounting Filesystem 5cd71ab5-2d11-4c18-97dd-71708f40e551
> 
> Great work, Matthew!
> 
> (Now I just need to check why copying data from NFS crashes ...)
> 
Hmm. And for that I'm hitting include/linux/pagemap.h:1250 pretty 
consistently; something's going haywire with readahead.

Matthew, are you sure that this one:

/** 

  * readahead_length - The number of bytes in this readahead request. 

  * @rac: The readahead request. 

  */
static inline size_t readahead_length(struct readahead_control *rac)
{
         return rac->_nr_pages * PAGE_SIZE;
}

is tenable for large folios?
Especially as we have in mm/readahead.c:499

         ractl->_nr_pages += 1UL << order;

Hmm?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman