On Fri, Mar 26, 2010 at 3:38 PM, Andreas Dilger <adilger@xxxxxxxxx> wrote:
On 2010-03-26, at 16:05, Arun Nair wrote:Not in the near future, unless you are running on PPC/ARM/SPARC that can also handle large pages.
So I'm guessing switching the system to 64-bit would fix this for us. How about increasing the block size from the current 4k? Would that be an option too?
_______________________________________________On Fri, Mar 26, 2010 at 2:10 PM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
On 03/26/2010 03:50 PM, Arun Nair wrote:
> Eric,
>
> Thanks for the quick reply... see my responses inline...
>
> On Fri, Mar 26, 2010 at 12:16 PM, Eric Sandeen <sandeen@xxxxxxxxxx
> <mailto:sandeen@xxxxxxxxxx>> wrote:
>
> On 03/26/2010 01:52 PM, Arun Nair wrote:
> > Hi -
> >
> > (I apologize for the ext4 question in an ext3 mailer, but I couldn't
> > find a user list for ext4.)
>
> linux-ext4@xxxxxxxxxxxxxxx <mailto:linux-ext4@xxxxxxxxxxxxxxx> :)
> but that's ok.
>
>
> Saw that but thought it was a dev-only list, sorry. Next time :)
*shrug* I think user questions are welcome too. At least I don't mind.
...
> dd fails as mentioned above. xfs_io errors too:
> [root@camanoe]# xfs_io -F -f -c "pwrite 8T 1M" bigfile2
> pwrite64: File too large
Oh. Well, then! Must be something else.
oh, ok:
sbi->s_bitmap_maxbytes = ext4_max_bitmap_size();
static loff_t ext4_max_size(int blkbits, int has_huge_files)
{
loff_t res;
loff_t upper_limit = MAX_LFS_FILESIZE;
<snip>
/* Sanity check against vm- & vfs- imposed limits */
if (res > upper_limit)
res = upper_limit;
return res;
}
and:
/* Page cache limit. The filesystems should put that into their s_maxbytes
limits, otherwise bad things can happen in VM. */
#if BITS_PER_LONG==32
#define MAX_LFS_FILESIZE (((u64)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1)
so it's only giving us 31 bits of pages, not 32. This limits it to 8T
on a 32-bit machine with 4k pages.
I'm not honestly sure if there is anything in the vm that can't actually
cope with a 32-bit offset... but until proven otherwise, probably not
going to change this without a lot of testing & inspection.
-Eric
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Cheers, Andreas
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