From: Badari Pulavarty 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 Signed-off-by: Badari Pulavarty Signed-off-by: Andrew Morton --- fs/buffer.c | 6 ++++-- fs/ocfs2/journal.c | 2 +- fs/reiserfs/prints.c | 2 +- include/linux/buffer_head.h | 19 +++++++++++-------- 4 files changed, 17 insertions(+), 12 deletions(-) diff -puN fs/buffer.c~change-buffer_headb_size-to-size_t fs/buffer.c --- devel/fs/buffer.c~change-buffer_headb_size-to-size_t 2006-03-11 02:47:08.000000000 -0800 +++ devel-akpm/fs/buffer.c 2006-03-11 02:47:08.000000000 -0800 @@ -426,8 +426,10 @@ __find_get_block_slow(struct block_devic if (all_mapped) { printk("__find_get_block_slow() failed. " "block=%llu, b_blocknr=%llu\n", - (unsigned long long)block, (unsigned long long)bh->b_blocknr); - printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); + (unsigned long long)block, + (unsigned long long)bh->b_blocknr); + printk("b_state=0x%08lx, b_size=%zu\n", + bh->b_state, bh->b_size); printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); } out_unlock: diff -puN fs/ocfs2/journal.c~change-buffer_headb_size-to-size_t fs/ocfs2/journal.c --- devel/fs/ocfs2/journal.c~change-buffer_headb_size-to-size_t 2006-03-11 02:47:08.000000000 -0800 +++ devel-akpm/fs/ocfs2/journal.c 2006-03-11 02:47:08.000000000 -0800 @@ -377,7 +377,7 @@ int ocfs2_journal_access(struct ocfs2_jo BUG_ON(!bh); BUG_ON(!(handle->flags & OCFS2_HANDLE_STARTED)); - mlog_entry("bh->b_blocknr=%llu, type=%d (\"%s\"), bh->b_size = %hu\n", + mlog_entry("bh->b_blocknr=%llu, type=%d (\"%s\"), bh->b_size = %zu\n", (unsigned long long)bh->b_blocknr, type, (type == OCFS2_JOURNAL_ACCESS_CREATE) ? "OCFS2_JOURNAL_ACCESS_CREATE" : diff -puN fs/reiserfs/prints.c~change-buffer_headb_size-to-size_t fs/reiserfs/prints.c --- devel/fs/reiserfs/prints.c~change-buffer_headb_size-to-size_t 2006-03-11 02:47:08.000000000 -0800 +++ devel-akpm/fs/reiserfs/prints.c 2006-03-11 02:47:08.000000000 -0800 @@ -143,7 +143,7 @@ static void sprintf_buffer_head(char *bu char b[BDEVNAME_SIZE]; sprintf(buf, - "dev %s, size %d, blocknr %llu, count %d, state 0x%lx, page %p, (%s, %s, %s)", + "dev %s, size %zd, blocknr %llu, count %d, state 0x%lx, page %p, (%s, %s, %s)", bdevname(bh->b_bdev, b), bh->b_size, (unsigned long long)bh->b_blocknr, atomic_read(&(bh->b_count)), bh->b_state, bh->b_page, diff -puN include/linux/buffer_head.h~change-buffer_headb_size-to-size_t include/linux/buffer_head.h --- devel/include/linux/buffer_head.h~change-buffer_headb_size-to-size_t 2006-03-11 02:47:08.000000000 -0800 +++ devel-akpm/include/linux/buffer_head.h 2006-03-11 02:47:08.000000000 -0800 @@ -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 */ }; /* _