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SubjectRe: [PATCH] remove 2TB block device limit
At 05:05 10/05/02, Andrew Morton wrote:
>Peter Chubb wrote:
> >
> > Hi,
> > At present, linux is limited to 2TB filesystems even on 64-bit
> > systems, because there are various places where the block offset on
> > disc are assigned to unsigned or int 32-bit variables.
> >
> > There's a type, sector_t, that's meant to hold offsets in sectors and
> > blocks. It's not used consistently (yet).
> >
> > The patch at
> > http://www.gelato.unsw.edu.au/patches/2.5.14-largefile-patch
> >
> > ...
> >
> > As this touches lots of places -- the generic block layer (Andrew?)
> > the IDE code (Martin?) and RAID (Neil?) and minor changes to the scsi
> > I've CCd a few people directly.
>
>That would be more Jens and aviro than I.
>
>My vote would be: just merge the sucker while it still (almost)
>applies. 2TB is a showstopper for some people in 2.4 today. Obviously
>2.6 will need 64-bit block numbers.
>
>The next obstacle will be page cache indices into the blockdev mapping.
>That's either an 8TB or 16TB limit, depending on signedness correctness.
>
>One minor point - it is currently not possible to print sector_t's.
>This code:
>
> printk("%lu%s", some_sector, some_string);
>
>will work fine with 32-bit sector_t. But with 64-bit sector_t it
>will generate a warning at compile-time and an oops at runtime.
>
>The same problem applies to dma_addr_t. Jeff, davem and I kicked
>that around a while back and ended up deciding that although there
>are a number of high-tech solutions, the dumb one was best:

Why not the even dumber one? Forget FMT_SECTOR_T and always use %Lu and
typecast (unsigned long long)sector_t_variable in the printk.

May be ugly, but isn't it correct that you actually need the above typecast
on some architectures where %Lu == unsigned long long != u64?

Anton

>--- 2.5.14/include/linux/types.h~sector_t-printing Thu May 9
>17:08:13 2002
>+++ 2.5.14-akpm/include/linux/types.h Thu May 9 17:08:13 2002
>@@ -120,8 +120,10 @@ typedef __s64 int64_t;
>
> #ifdef BLK_64BIT_SECTOR
> typedef u64 sector_t;
>+#define FMT_SECTOR_T "%Lu"
> #else
> typedef unsigned long sector_t;
>+#define FMT_SECTOR_T "%lu"
> #endif
>
> #endif /* __KERNEL_STRICT_NAMES */
>--- 2.5.14/fs/buffer.c~sector_t-printing Thu May 9 17:08:13 2002
>+++ 2.5.14-akpm/fs/buffer.c Thu May 9 17:09:35 2002
>@@ -179,7 +179,8 @@ __clear_page_buffers(struct page *page)
>
> static void buffer_io_error(struct buffer_head *bh)
> {
>- printk(KERN_ERR "Buffer I/O error on device %s, logical block %ld\n",
>+ printk(KERN_ERR "Buffer I/O error on device %s,"
>+ " logical block " FMT_SECTOR_T "\n",
> bdevname(bh->b_bdev), bh->b_blocknr);
> }
>-
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--
"I've not lost my mind. It's backed up on tape somewhere." - Unknown
--
Anton Altaparmakov <aia21 at cantab.net> (replace at with @)
Linux NTFS Maintainer / IRC: #ntfs on irc.openprojects.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/

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