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[PATCH] change buffer_head.b_size to size_t

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Increase the size of the buffer_head b_size field (only) for 64 bit platforms.
Update some old and moldy comments in and around the structure as well.

The b_size increase allows us to perform larger mappings and allocations for
large I/O requests from userspace, which tie in with other changes allowing
the get_block_t() interface to map multiple blocks at once.

Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Badari Pulavarty 2006-03-26 01:38:00 -08:00 • committed by Linus Torvalds
parent d48589bfad
commit 205f87f6b3
4 changed files with 17 additions and 12 deletions
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19
include/linux/buffer_head.h
View file

@ -46,25 +46,28 @@ struct address_space;
typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
/*
* Keep related fields in common cachelines. The most commonly accessed
* field (b_state) goes at the start so the compiler does not generate
* indexed addressing for it.
* Historically, a buffer_head was used to map a single block
* within a page, and of course as the unit of I/O through the
* filesystem and block layers. Nowadays the basic I/O unit
* is the bio, and buffer_heads are used for extracting block
* mappings (via a get_block_t call), for tracking state within
* a page (via a page_mapping) and for wrapping bio submission
* for backward compatibility reasons (e.g. submit_bh).
*/
struct buffer_head {
/* First cache line: */
unsigned long b_state; /* buffer state bitmap (see above) */
struct buffer_head *b_this_page;/* circular list of page's buffers */
struct page *b_page; /* the page this bh is mapped to */
atomic_t b_count; /* users using this block */
u32 b_size; /* block size */
sector_t b_blocknr; /* block number */
char *b_data; /* pointer to data block */
sector_t b_blocknr; /* start block number */
size_t b_size; /* size of mapping */
char *b_data; /* pointer to data within the page */
struct block_device *b_bdev;
bh_end_io_t *b_end_io; /* I/O completion */
void *b_private; /* reserved for b_end_io */
struct list_head b_assoc_buffers; /* associated with another mapping */
atomic_t b_count; /* users using this buffer_head */
};
/*