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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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