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SubjectRe: patch: aio + bio for raw io
On Fri, Feb 08, 2002 at 02:53:13AM -0500, Benjamin LaHaise wrote:
> Quick message: this patch makes aio use bio directly for brw_kvec_async.
> This is against yesterday's patchset. Comments?
>

I was looking for this in yesterday's aio patchset for 2.5 and was just
about to send you a note asking you about this :)

You chose to add a kvec_cb field to the bio structure rather than use
bi_private ?

For the raw path, you are OK since you never have to copy data out of
the kvecs after i/o completion, and unmap_kvec only looks at veclet pages.
So the fact block can change the offset and len fields in the veclets
doesn't affect you, but thought I'd mention it as a point of caution
anyhow ...

> -ben
>
> ===== fs/Makefile 1.15 vs 1.16 =====
> --- 1.15/fs/Makefile Wed Jan 30 02:21:55 2002
> +++ 1.16/fs/Makefile Fri Feb 8 14:57:54 2002
> @@ -22,6 +22,7 @@
> obj-y += noquot.o
> endif
>
> +export-objs += aio.o
> obj-y += aio.o
>
> subdir-$(CONFIG_PROC_FS) += proc
> ===== fs/buffer.c 1.60 vs 1.61 =====
> --- 1.60/fs/buffer.c Tue Jan 15 05:53:34 2002
> +++ 1.61/fs/buffer.c Fri Feb 8 17:22:14 2002
> @@ -54,6 +54,8 @@
> #include <asm/bitops.h>
> #include <asm/mmu_context.h>
>
> +extern struct bio *bio_setup_from_kvec(int gfp_mask, struct kvec *kvec);
> +
> #define MAX_BUF_PER_PAGE (PAGE_CACHE_SIZE / 512)
> #define NR_RESERVED (10*MAX_BUF_PER_PAGE)
> #define MAX_UNUSED_BUFFERS NR_RESERVED+20 /* don't ever have more than this
> @@ -2764,16 +2766,26 @@
> * It is up to the caller to make sure that there are enough blocks
> * passed in to completely map the iobufs to disk.
> */
> +static int brw_kvec_end_io(struct bio *bio, int nr_sectors)
> +{
> + kvec_cb_t cb = bio->cb;
> + int res = nr_sectors * 512;
> + if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
> + res = -EIO;
> + bio_put(bio);
> + cb.fn(cb.data, cb.vec, res);
> + return 0;
> +}
>
> -int brw_kvec_async(int rw, kvec_cb_t cb, kdev_t dev, unsigned blocks, unsigned long blknr, int sector_shift)
> +int brw_kvec_async(int rw, kvec_cb_t cb, kdev_t dev, unsigned blocks, sector_t blknr, int sector_shift)
> {
> struct kvec *vec = cb.vec;
> struct kveclet *veclet;
> - int err;
> int length;
> unsigned sector_size = 1 << sector_shift;
> int i;
>
> + struct bio *bio;
> struct brw_cb *brw_cb;
>
> if (!vec->nr)
> @@ -2795,125 +2807,21 @@
> if (length < (blocks << sector_shift))
> BUG();
>
> - /*
> - * OK to walk down the iovec doing page IO on each page we find.
> - */
> - err = 0;
> -
> if (!blocks) {
> printk("brw_kiovec_async: !i\n");
> return -EINVAL;
> }
>
> - /* FIXME: tie into userbeans here */
> - brw_cb = kmalloc(sizeof(*brw_cb) + (blocks * sizeof(struct buffer_head *)), GFP_KERNEL);
> - if (!brw_cb)
> + bio = bio_setup_from_kvec(GFP_KERNEL, vec);
> + if (unlikely(!bio))
> return -ENOMEM;
> -
> - brw_cb->cb = cb;
> - brw_cb->nr = 0;
> -
> - /* This is ugly. FIXME. */
> - for (i=0, veclet=vec->veclet; i<vec->nr; i++,veclet++) {
> - struct page *page = veclet->page;
> - unsigned offset = veclet->offset;
> - unsigned length = veclet->length;
> -
> - if (!page)
> - BUG();
> -
> - while (length > 0) {
> - struct buffer_head *tmp;
> - tmp = kmem_cache_alloc(bh_cachep, GFP_NOIO);
> - err = -ENOMEM;
> - if (!tmp)
> - goto error;
> -
> - tmp->b_dev = B_FREE;
> - tmp->b_size = sector_size;
> - set_bh_page(tmp, page, offset);
> - tmp->b_this_page = tmp;
> -
> - init_buffer(tmp, end_buffer_io_kiobuf_async, NULL);
> - tmp->b_dev = dev;
> - tmp->b_blocknr = blknr++;
> - tmp->b_state = (1 << BH_Mapped) | (1 << BH_Lock)
> - | (1 << BH_Req);
> - tmp->b_private = brw_cb;
> -
> - if (rw == WRITE) {
> - set_bit(BH_Uptodate, &tmp->b_state);
> - clear_bit(BH_Dirty, &tmp->b_state);
> - }
> -
> - brw_cb->bh[brw_cb->nr++] = tmp;
> - length -= sector_size;
> - offset += sector_size;
> -
> - if (offset >= PAGE_SIZE) {
> - offset = 0;
> - break;
> - }
> -
> - if (brw_cb->nr >= blocks)
> - goto submit;
> - } /* End of block loop */
> - } /* End of page loop */
> -
> -submit:
> - atomic_set(&brw_cb->io_count, brw_cb->nr+1);
> - /* okay, we've setup all our io requests, now fire them off! */
> - for (i=0; i<brw_cb->nr; i++)
> - submit_bh(rw, brw_cb->bh[i]);
> - brw_cb_put(brw_cb);
> + bio->cb = cb;
> + bio->bi_sector = blknr;
> + bio->bi_dev = dev;
> + bio->bi_vcnt = vec->nr;
> + bio->bi_size = length;
> + bio->bi_end_io = brw_kvec_end_io;
> + submit_bio(rw, bio);
>
> return 0;
> -
> -error:
> - /* Walk brw_cb_table freeing all the goop associated with each kiobuf */
> - if (brw_cb) {
> - /* We got an error allocating the bh'es. Just free the current
> - buffer_heads and exit. */
> - for (i=0; i<brw_cb->nr; i++)
> - kmem_cache_free(bh_cachep, brw_cb->bh[i]);
> - kfree(brw_cb);
> - }
> -
> - return err;
> -}
> -#if 0
> -int brw_kiovec(int rw, int nr, struct kiobuf *iovec[],
> - kdev_t dev, int nr_blocks, unsigned long b[], int sector_size)
> -{
> - int i;
> - int transferred = 0;
> - int err = 0;
> -
> - if (!nr)
> - return 0;
> -
> - /* queue up and trigger the io */
> - err = brw_kiovec_async(rw, nr, iovec, dev, nr_blocks, b, sector_size);
> - if (err)
> - goto out;
> -
> - /* wait on the last iovec first -- it's more likely to finish last */
> - for (i=nr; --i >= 0; )
> - kiobuf_wait_for_io(iovec[i]);
> -
> - run_task_queue(&tq_disk);
> -
> - /* okay, how much data actually got through? */
> - for (i=0; i<nr; i++) {
> - if (iovec[i]->errno) {
> - if (!err)
> - err = iovec[i]->errno;
> - break;
> - }
> - transferred += iovec[i]->length;
> - }
> -
> -out:
> - return transferred ? transferred : err;
> }
> -#endif
> ===== fs/bio.c 1.14 vs 1.15 =====
> --- 1.14/fs/bio.c Thu Feb 7 16:13:25 2002
> +++ 1.15/fs/bio.c Fri Feb 8 17:22:14 2002
> @@ -151,6 +151,22 @@
> return NULL;
> }
>
> +struct bio *bio_setup_from_kvec(int gfp_mask, struct kvec *kvec)
> +{
> + struct bio *bio = mempool_alloc(bio_pool, gfp_mask);
> + struct bio_vec *bvl = NULL;
> +
> + if (unlikely(!bio))
> + return NULL;
> +
> + bio->bi_max = kvec->max_nr;
> + bio_init(bio);
> + bio->bi_destructor = bio_destructor;
> + bio->bi_io_vec = (struct bio_vec *)kvec->veclet; /* shoot me */
> + bio->bi_flags |= 1 << BIO_CLONED; /* don't free the vec */
> + return bio;
> +}
> +
> /**
> * bio_put - release a reference to a bio
> * @bio: bio to release reference to
> ===== include/linux/kiovec.h 1.1 vs 1.2 =====
> --- 1.1/include/linux/kiovec.h Sat Jan 12 02:19:10 2002
> +++ 1.2/include/linux/kiovec.h Fri Feb 8 15:00:54 2002
> @@ -6,8 +6,8 @@
>
> struct kveclet {
> struct page *page;
> - unsigned offset;
> unsigned length;
> + unsigned offset;
> };
>
> struct kvec {
> ===== include/linux/bio.h 1.11 vs 1.12 =====
> --- 1.11/include/linux/bio.h Wed Feb 6 01:23:04 2002
> +++ 1.12/include/linux/bio.h Fri Feb 8 17:22:23 2002
> @@ -26,6 +26,8 @@
> #define BIO_VMERGE_BOUNDARY 0
> #endif
>
> +#include <linux/kiovec.h>
> +
> #define BIO_DEBUG
>
> #ifdef BIO_DEBUG
> @@ -91,6 +93,7 @@
> void *bi_private;
>
> bio_destructor_t *bi_destructor; /* destructor */
> + kvec_cb_t cb;
> };
>
> /*
> ===== fs/aio.c 1.1 vs 1.2 =====
> --- 1.1/fs/aio.c Wed Jan 30 13:12:34 2002
> +++ 1.2/fs/aio.c Fri Feb 8 14:58:10 2002
> @@ -37,6 +37,7 @@
> #include <linux/smp_lock.h>
> #include <linux/compiler.h>
> #include <linux/poll.h>
> +#include <linux/module.h>
>
> #include <asm/uaccess.h>
>
> @@ -964,3 +965,8 @@
> }
>
> __initcall(aio_setup);
> +EXPORT_SYMBOL_GPL(generic_file_kvec_read);
> +EXPORT_SYMBOL_GPL(generic_file_aio_read);
> +EXPORT_SYMBOL_GPL(generic_file_kvec_write);
> +EXPORT_SYMBOL_GPL(generic_file_aio_write);
> +EXPORT_SYMBOL_GPL(generic_file_new_read);
> --
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> the body to majordomo@kvack.org. For more info on Linux AIO,
> see: http://www.kvack.org/aio/
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