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    SubjectRe: [PATCH] remove 2TB block device limit
    Peter Chubb wrote:
    > ...
    > Christoph> - why is the get_block block argument
    > Christoph> a sector_t? It presents a logical filesystem block which
    > Christoph> usually is larger than the sector, not to mention that for
    > Christoph> the usual blocksize == PAGE_SIZE case a ulong is enough as
    > Christoph> that is the same size the pagecache limit triggers.
    > For filesystems that *can* handle logical filesystem blocks beyond the
    > 2^32 limit (i.e., that use >32bit offsets in their on-disc format),
    > the get_block() argument has to be > 32bits long. At the moment
    > that's only JFS and XFS, but reiserfs version 4 looks as if it might
    > go that way. We'll need this especially when the pagecache limit is
    > gone.

    I think Christoph's point is that a pagecache index is not a sector
    number. We agree that we need to plan for taking it to 64 bits, but
    it should be something different. Like pageindex_t, or whatever.


    --- linux-2.5.15/include/linux/mm.h Tue Apr 30 17:56:30 2002
    +++ 25/include/linux/mm.h Mon May 13 19:08:21 2002
    @@ -148,7 +148,7 @@ struct vm_operations_struct {
    typedef struct page {
    struct list_head list; /* ->mapping has some page lists. */
    struct address_space *mapping; /* The inode (or ...) we belong to. */
    - unsigned long index; /* Our offset within mapping. */
    + sector_t index; /* Our offset within mapping. */
    atomic_t count; /* Usage count, see below. */
    unsigned long flags; /* atomic flags, some possibly
    updated asynchronously */
    looks rather silly, no?

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