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| author | Badari Pulavarty <pbadari@us.ibm.com> | 2006-03-26 01:38:00 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-26 08:57:01 -0800 |
| commit | 205f87f6b342444f722e4559d33318686f7df2ca (patch) | |
| tree | 61f32bb0582dde9fd62ee3d03ac3324b949b29e6 /include/linux/buffer_head.h | |
| parent | d48589bfad0e60bff0aa3f9e4875983f607bd44b (diff) | |
| download | op-kernel-dev-205f87f6b342444f722e4559d33318686f7df2ca.zip op-kernel-dev-205f87f6b342444f722e4559d33318686f7df2ca.tar.gz | |
[PATCH] change buffer_head.b_size to size_t
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>
Diffstat (limited to 'include/linux/buffer_head.h')
| -rw-r--r-- | include/linux/buffer_head.h | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index da917ed..464f068 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -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 */ }; /* |
