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Date: Thu, 11 Apr 2013 22:04:35 +0800
From: Zheng Liu <gnehzuil.liu@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 02/29] ext4: Use io_end for multiple bios
On Mon, Apr 08, 2013 at 11:32:07PM +0200, Jan Kara wrote:
> Change writeback path to create just one io_end structure for the extent
> to which we submit IO and share it among bios writing that extent. This
> prevents needless splitting and joining of unwritten extents when they
> cannot be submitted as a single bio.
>
> Signed-off-by: Jan Kara <jack@...e.cz>
Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
Regards,
- Zheng
> ---
> fs/ext4/ext4.h | 8 +++-
> fs/ext4/inode.c | 85 ++++++++++++++++++++-----------------
> fs/ext4/page-io.c | 121 +++++++++++++++++++++++++++++++++--------------------
> 3 files changed, 128 insertions(+), 86 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 3c70547..edf9b9e 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -207,6 +207,7 @@ typedef struct ext4_io_end {
> ssize_t size; /* size of the extent */
> struct kiocb *iocb; /* iocb struct for AIO */
> int result; /* error value for AIO */
> + atomic_t count; /* reference counter */
> } ext4_io_end_t;
>
> struct ext4_io_submit {
> @@ -2601,11 +2602,14 @@ extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
>
> /* page-io.c */
> extern int __init ext4_init_pageio(void);
> -extern void ext4_add_complete_io(ext4_io_end_t *io_end);
> extern void ext4_exit_pageio(void);
> extern void ext4_ioend_wait(struct inode *);
> -extern void ext4_free_io_end(ext4_io_end_t *io);
> extern ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags);
> +extern ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end);
> +extern int ext4_put_io_end(ext4_io_end_t *io_end);
> +extern void ext4_put_io_end_defer(ext4_io_end_t *io_end);
> +extern void ext4_io_submit_init(struct ext4_io_submit *io,
> + struct writeback_control *wbc);
> extern void ext4_end_io_work(struct work_struct *work);
> extern void ext4_io_submit(struct ext4_io_submit *io);
> extern int ext4_bio_write_page(struct ext4_io_submit *io,
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 6b8ec2a..ba07412 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1409,7 +1409,10 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
> struct ext4_io_submit io_submit;
>
> BUG_ON(mpd->next_page <= mpd->first_page);
> - memset(&io_submit, 0, sizeof(io_submit));
> + ext4_io_submit_init(&io_submit, mpd->wbc);
> + io_submit.io_end = ext4_init_io_end(inode, GFP_NOFS);
> + if (!io_submit.io_end)
> + return -ENOMEM;
> /*
> * We need to start from the first_page to the next_page - 1
> * to make sure we also write the mapped dirty buffer_heads.
> @@ -1497,6 +1500,8 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
> pagevec_release(&pvec);
> }
> ext4_io_submit(&io_submit);
> + /* Drop io_end reference we got from init */
> + ext4_put_io_end_defer(io_submit.io_end);
> return ret;
> }
>
> @@ -2116,9 +2121,16 @@ static int ext4_writepage(struct page *page,
> */
> return __ext4_journalled_writepage(page, len);
>
> - memset(&io_submit, 0, sizeof(io_submit));
> + ext4_io_submit_init(&io_submit, wbc);
> + io_submit.io_end = ext4_init_io_end(inode, GFP_NOFS);
> + if (!io_submit.io_end) {
> + redirty_page_for_writepage(wbc, page);
> + return -ENOMEM;
> + }
> ret = ext4_bio_write_page(&io_submit, page, len, wbc);
> ext4_io_submit(&io_submit);
> + /* Drop io_end reference we got from init */
> + ext4_put_io_end_defer(io_submit.io_end);
> return ret;
> }
>
> @@ -2957,9 +2969,13 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
> struct inode *inode = file_inode(iocb->ki_filp);
> ext4_io_end_t *io_end = iocb->private;
>
> - /* if not async direct IO or dio with 0 bytes write, just return */
> - if (!io_end || !size)
> - goto out;
> + /* if not async direct IO just return */
> + if (!io_end) {
> + inode_dio_done(inode);
> + if (is_async)
> + aio_complete(iocb, ret, 0);
> + return;
> + }
>
> ext_debug("ext4_end_io_dio(): io_end 0x%p "
> "for inode %lu, iocb 0x%p, offset %llu, size %zd\n",
> @@ -2967,25 +2983,13 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
> size);
>
> iocb->private = NULL;
> -
> - /* if not aio dio with unwritten extents, just free io and return */
> - if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
> - ext4_free_io_end(io_end);
> -out:
> - inode_dio_done(inode);
> - if (is_async)
> - aio_complete(iocb, ret, 0);
> - return;
> - }
> -
> io_end->offset = offset;
> io_end->size = size;
> if (is_async) {
> io_end->iocb = iocb;
> io_end->result = ret;
> }
> -
> - ext4_add_complete_io(io_end);
> + ext4_put_io_end_defer(io_end);
> }
>
> /*
> @@ -3019,6 +3023,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
> get_block_t *get_block_func = NULL;
> int dio_flags = 0;
> loff_t final_size = offset + count;
> + ext4_io_end_t *io_end = NULL;
>
> /* Use the old path for reads and writes beyond i_size. */
> if (rw != WRITE || final_size > inode->i_size)
> @@ -3057,13 +3062,16 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
> iocb->private = NULL;
> ext4_inode_aio_set(inode, NULL);
> if (!is_sync_kiocb(iocb)) {
> - ext4_io_end_t *io_end = ext4_init_io_end(inode, GFP_NOFS);
> + io_end = ext4_init_io_end(inode, GFP_NOFS);
> if (!io_end) {
> ret = -ENOMEM;
> goto retake_lock;
> }
> io_end->flag |= EXT4_IO_END_DIRECT;
> - iocb->private = io_end;
> + /*
> + * Grab reference for DIO. Will be dropped in ext4_end_io_dio()
> + */
> + iocb->private = ext4_get_io_end(io_end);
> /*
> * we save the io structure for current async direct
> * IO, so that later ext4_map_blocks() could flag the
> @@ -3087,26 +3095,27 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
> NULL,
> dio_flags);
>
> - if (iocb->private)
> - ext4_inode_aio_set(inode, NULL);
> /*
> - * The io_end structure takes a reference to the inode, that
> - * structure needs to be destroyed and the reference to the
> - * inode need to be dropped, when IO is complete, even with 0
> - * byte write, or failed.
> - *
> - * In the successful AIO DIO case, the io_end structure will
> - * be destroyed and the reference to the inode will be dropped
> - * after the end_io call back function is called.
> - *
> - * In the case there is 0 byte write, or error case, since VFS
> - * direct IO won't invoke the end_io call back function, we
> - * need to free the end_io structure here.
> + * Put our reference to io_end. This can free the io_end structure e.g.
> + * in sync IO case or in case of error. It can even perform extent
> + * conversion if all bios we submitted finished before we got here.
> + * Note that in that case iocb->private can be already set to NULL
> + * here.
> */
> - if (ret != -EIOCBQUEUED && ret <= 0 && iocb->private) {
> - ext4_free_io_end(iocb->private);
> - iocb->private = NULL;
> - } else if (ret > 0 && !overwrite && ext4_test_inode_state(inode,
> + if (io_end) {
> + ext4_inode_aio_set(inode, NULL);
> + ext4_put_io_end(io_end);
> + /*
> + * In case of error or no write ext4_end_io_dio() was not
> + * called so we have to put iocb's reference.
> + */
> + if (ret <= 0 && ret != -EIOCBQUEUED) {
> + WARN_ON(iocb->private != io_end);
> + ext4_put_io_end(io_end);
> + iocb->private = NULL;
> + }
> + }
> + if (ret > 0 && !overwrite && ext4_test_inode_state(inode,
> EXT4_STATE_DIO_UNWRITTEN)) {
> int err;
> /*
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 73bc011..da8bddf 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -51,17 +51,28 @@ void ext4_ioend_wait(struct inode *inode)
> wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_ioend_count) == 0));
> }
>
> -void ext4_free_io_end(ext4_io_end_t *io)
> +static void ext4_release_io_end(ext4_io_end_t *io_end)
> {
> - int i;
> + BUG_ON(!list_empty(&io_end->list));
> + BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
> +
> + if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
> + wake_up_all(ext4_ioend_wq(io_end->inode));
> + if (io_end->flag & EXT4_IO_END_DIRECT)
> + inode_dio_done(io_end->inode);
> + if (io_end->iocb)
> + aio_complete(io_end->iocb, io_end->result, 0);
> + kmem_cache_free(io_end_cachep, io_end);
> +}
>
> - BUG_ON(!io);
> - BUG_ON(!list_empty(&io->list));
> - BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN);
> +static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
> +{
> + struct inode *inode = io_end->inode;
>
> - if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count))
> - wake_up_all(ext4_ioend_wq(io->inode));
> - kmem_cache_free(io_end_cachep, io);
> + io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
> + /* Wake up anyone waiting on unwritten extent conversion */
> + if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
> + wake_up_all(ext4_ioend_wq(inode));
> }
>
> /* check a range of space and convert unwritten extents to written. */
> @@ -84,13 +95,8 @@ static int ext4_end_io(ext4_io_end_t *io)
> "(inode %lu, offset %llu, size %zd, error %d)",
> inode->i_ino, offset, size, ret);
> }
> - /* Wake up anyone waiting on unwritten extent conversion */
> - if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
> - wake_up_all(ext4_ioend_wq(inode));
> - if (io->flag & EXT4_IO_END_DIRECT)
> - inode_dio_done(inode);
> - if (io->iocb)
> - aio_complete(io->iocb, io->result, 0);
> + ext4_clear_io_unwritten_flag(io);
> + ext4_release_io_end(io);
> return ret;
> }
>
> @@ -121,7 +127,7 @@ static void dump_completed_IO(struct inode *inode)
> }
>
> /* Add the io_end to per-inode completed end_io list. */
> -void ext4_add_complete_io(ext4_io_end_t *io_end)
> +static void ext4_add_complete_io(ext4_io_end_t *io_end)
> {
> struct ext4_inode_info *ei = EXT4_I(io_end->inode);
> struct workqueue_struct *wq;
> @@ -158,8 +164,6 @@ static int ext4_do_flush_completed_IO(struct inode *inode)
> err = ext4_end_io(io);
> if (unlikely(!ret && err))
> ret = err;
> - io->flag &= ~EXT4_IO_END_UNWRITTEN;
> - ext4_free_io_end(io);
> }
> return ret;
> }
> @@ -191,10 +195,43 @@ ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
> atomic_inc(&EXT4_I(inode)->i_ioend_count);
> io->inode = inode;
> INIT_LIST_HEAD(&io->list);
> + atomic_set(&io->count, 1);
> }
> return io;
> }
>
> +void ext4_put_io_end_defer(ext4_io_end_t *io_end)
> +{
> + if (atomic_dec_and_test(&io_end->count)) {
> + if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
> + ext4_release_io_end(io_end);
> + return;
> + }
> + ext4_add_complete_io(io_end);
> + }
> +}
> +
> +int ext4_put_io_end(ext4_io_end_t *io_end)
> +{
> + int err = 0;
> +
> + if (atomic_dec_and_test(&io_end->count)) {
> + if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
> + err = ext4_convert_unwritten_extents(io_end->inode,
> + io_end->offset, io_end->size);
> + ext4_clear_io_unwritten_flag(io_end);
> + }
> + ext4_release_io_end(io_end);
> + }
> + return err;
> +}
> +
> +ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
> +{
> + atomic_inc(&io_end->count);
> + return io_end;
> +}
> +
> /*
> * Print an buffer I/O error compatible with the fs/buffer.c. This
> * provides compatibility with dmesg scrapers that look for a specific
> @@ -277,12 +314,7 @@ static void ext4_end_bio(struct bio *bio, int error)
> bi_sector >> (inode->i_blkbits - 9));
> }
>
> - if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
> - ext4_free_io_end(io_end);
> - return;
> - }
> -
> - ext4_add_complete_io(io_end);
> + ext4_put_io_end_defer(io_end);
> }
>
> void ext4_io_submit(struct ext4_io_submit *io)
> @@ -296,40 +328,37 @@ void ext4_io_submit(struct ext4_io_submit *io)
> bio_put(io->io_bio);
> }
> io->io_bio = NULL;
> - io->io_op = 0;
> +}
> +
> +void ext4_io_submit_init(struct ext4_io_submit *io,
> + struct writeback_control *wbc)
> +{
> + io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
> + io->io_bio = NULL;
> io->io_end = NULL;
> }
>
> -static int io_submit_init(struct ext4_io_submit *io,
> - struct inode *inode,
> - struct writeback_control *wbc,
> - struct buffer_head *bh)
> +static int io_submit_init_bio(struct ext4_io_submit *io,
> + struct buffer_head *bh)
> {
> - ext4_io_end_t *io_end;
> - struct page *page = bh->b_page;
> int nvecs = bio_get_nr_vecs(bh->b_bdev);
> struct bio *bio;
>
> - io_end = ext4_init_io_end(inode, GFP_NOFS);
> - if (!io_end)
> - return -ENOMEM;
> bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
> bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
> bio->bi_bdev = bh->b_bdev;
> - bio->bi_private = io->io_end = io_end;
> bio->bi_end_io = ext4_end_bio;
> -
> - io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
> -
> + bio->bi_private = ext4_get_io_end(io->io_end);
> + if (!io->io_end->size)
> + io->io_end->offset = (bh->b_page->index << PAGE_CACHE_SHIFT)
> + + bh_offset(bh);
> io->io_bio = bio;
> - io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
> io->io_next_block = bh->b_blocknr;
> return 0;
> }
>
> static int io_submit_add_bh(struct ext4_io_submit *io,
> struct inode *inode,
> - struct writeback_control *wbc,
> struct buffer_head *bh)
> {
> ext4_io_end_t *io_end;
> @@ -340,18 +369,18 @@ submit_and_retry:
> ext4_io_submit(io);
> }
> if (io->io_bio == NULL) {
> - ret = io_submit_init(io, inode, wbc, bh);
> + ret = io_submit_init_bio(io, bh);
> if (ret)
> return ret;
> }
> + ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
> + if (ret != bh->b_size)
> + goto submit_and_retry;
> io_end = io->io_end;
> if (buffer_uninit(bh))
> ext4_set_io_unwritten_flag(inode, io_end);
> - io->io_end->size += bh->b_size;
> + io_end->size += bh->b_size;
> io->io_next_block++;
> - ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
> - if (ret != bh->b_size)
> - goto submit_and_retry;
> return 0;
> }
>
> @@ -423,7 +452,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> do {
> if (!buffer_async_write(bh))
> continue;
> - ret = io_submit_add_bh(io, inode, wbc, bh);
> + ret = io_submit_add_bh(io, inode, bh);
> if (ret) {
> /*
> * We only get here on ENOMEM. Not much else
> --
> 1.7.1
>
> --
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