Messages in this thread Patch in this message | | | Subject | Re: [PATCH] change b_size to size_t | From | Badari Pulavarty <> | Date | Thu, 23 Feb 2006 10:46:27 -0800 |
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On Thu, 2006-02-23 at 12:29 -0500, Benjamin LaHaise wrote: > On Thu, Feb 23, 2006 at 09:28:58AM -0800, Badari Pulavarty wrote: > > How about doing this ? Change b_state to u32 and change b_size > > to "size_t". This way, we don't increase the overall size of > > the structure on 64-bit machines. Isn't it ? > > I was thinking of that too, but that doesn't work with the bit operations > on big endian machines (which require unsigned long). Oh well, I guess > that even with adding an extra 8 bytes on x86-64 we're still at the 96 > bytes, or 92 bytes if the atomic_t is put at the end of the struct. > > -ben
Okay. Here is the final version (hopefully). I moved atomic_t to end of the structure. I still see 96-bytes for x86-64 also :(
buffer_head 40425 40760 96 40 1 : tunables 120 60 8 : slabdata 1019 1019 0
Thanks, Badari
Increase the size of the buffer_head b_size field 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 Pulavary <pbadari@us.ibm.com>
Index: linux-2.6.16-rc4/include/linux/buffer_head.h =================================================================== --- linux-2.6.16-rc4.orig/include/linux/buffer_head.h 2006-02-17 14:23:45.000000000 -0800 +++ linux-2.6.16-rc4/include/linux/buffer_head.h 2006-02-23 10:15:33.000000000 -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 */ }; /* Index: linux-2.6.16-rc4/fs/buffer.c =================================================================== --- linux-2.6.16-rc4.orig/fs/buffer.c 2006-02-17 14:23:45.000000000 -0800 +++ linux-2.6.16-rc4/fs/buffer.c 2006-02-23 08:55:18.000000000 -0800 @@ -432,7 +432,8 @@ __find_get_block_slow(struct block_devic 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); + printk("b_state=0x%08lx, b_size=%lu\n", bh->b_state, + (unsigned long)bh->b_size); printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); } out_unlock: Index: linux-2.6.16-rc4/fs/reiserfs/prints.c =================================================================== --- linux-2.6.16-rc4.orig/fs/reiserfs/prints.c 2006-02-17 14:23:45.000000000 -0800 +++ linux-2.6.16-rc4/fs/reiserfs/prints.c 2006-02-23 08:56:17.000000000 -0800 @@ -143,8 +143,8 @@ 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)", - bdevname(bh->b_bdev, b), bh->b_size, + "dev %s, size %ld, blocknr %llu, count %d, state 0x%lx, page %p, (%s, %s, %s)", + bdevname(bh->b_bdev, b), (unsigned long)bh->b_size, (unsigned long long)bh->b_blocknr, atomic_read(&(bh->b_count)), bh->b_state, bh->b_page, buffer_uptodate(bh) ? "UPTODATE" : "!UPTODATE", Index: linux-2.6.16-rc4/fs/ocfs2/journal.c =================================================================== --- linux-2.6.16-rc4.orig/fs/ocfs2/journal.c 2006-02-17 14:23:45.000000000 -0800 +++ linux-2.6.16-rc4/fs/ocfs2/journal.c 2006-02-23 08:56:55.000000000 -0800 @@ -377,12 +377,12 @@ 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 = %lu\n", (unsigned long long)bh->b_blocknr, type, (type == OCFS2_JOURNAL_ACCESS_CREATE) ? "OCFS2_JOURNAL_ACCESS_CREATE" : "OCFS2_JOURNAL_ACCESS_WRITE", - bh->b_size); + (unsigned long)bh->b_size); /* we can safely remove this assertion after testing. */ if (!buffer_uptodate(bh)) {
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