ext4: use bio layer instead of buffer layer in mpage_da_submit_io
Call the block I/O layer directly instad of going through the buffer
layer. This should give us much better performance and scalability,
as well as lowering our CPU utilization when doing buffered writeback.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
new file mode 100644
index 0000000..b972ca5
--- /dev/null
+++ b/fs/ext4/page-io.c
@@ -0,0 +1,430 @@
+/*
+ * linux/fs/ext4/page-io.c
+ *
+ * This contains the new page_io functions for ext4
+ *
+ * Written by Theodore Ts'o, 2010.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/time.h>
+#include <linux/jbd2.h>
+#include <linux/highuid.h>
+#include <linux/pagemap.h>
+#include <linux/quotaops.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/writeback.h>
+#include <linux/pagevec.h>
+#include <linux/mpage.h>
+#include <linux/namei.h>
+#include <linux/uio.h>
+#include <linux/bio.h>
+#include <linux/workqueue.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "ext4_jbd2.h"
+#include "xattr.h"
+#include "acl.h"
+#include "ext4_extents.h"
+
+static struct kmem_cache *io_page_cachep, *io_end_cachep;
+
+int __init init_ext4_pageio(void)
+{
+ io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
+ if (io_page_cachep == NULL)
+ return -ENOMEM;
+ io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
+ if (io_page_cachep == NULL) {
+ kmem_cache_destroy(io_page_cachep);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+void exit_ext4_pageio(void)
+{
+ kmem_cache_destroy(io_end_cachep);
+ kmem_cache_destroy(io_page_cachep);
+}
+
+void ext4_free_io_end(ext4_io_end_t *io)
+{
+ int i;
+
+ BUG_ON(!io);
+ if (io->page)
+ put_page(io->page);
+ for (i = 0; i < io->num_io_pages; i++) {
+ if (--io->pages[i]->p_count == 0) {
+ struct page *page = io->pages[i]->p_page;
+
+ end_page_writeback(page);
+ put_page(page);
+ kmem_cache_free(io_page_cachep, io->pages[i]);
+ }
+ }
+ io->num_io_pages = 0;
+ iput(io->inode);
+ kmem_cache_free(io_end_cachep, io);
+}
+
+/*
+ * check a range of space and convert unwritten extents to written.
+ */
+int ext4_end_io_nolock(ext4_io_end_t *io)
+{
+ struct inode *inode = io->inode;
+ loff_t offset = io->offset;
+ ssize_t size = io->size;
+ int ret = 0;
+
+ ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
+ "list->prev 0x%p\n",
+ io, inode->i_ino, io->list.next, io->list.prev);
+
+ if (list_empty(&io->list))
+ return ret;
+
+ if (!(io->flag & EXT4_IO_END_UNWRITTEN))
+ return ret;
+
+ ret = ext4_convert_unwritten_extents(inode, offset, size);
+ if (ret < 0) {
+ printk(KERN_EMERG "%s: failed to convert unwritten "
+ "extents to written extents, error is %d "
+ "io is still on inode %lu aio dio list\n",
+ __func__, ret, inode->i_ino);
+ return ret;
+ }
+
+ if (io->iocb)
+ aio_complete(io->iocb, io->result, 0);
+ /* clear the DIO AIO unwritten flag */
+ io->flag &= ~EXT4_IO_END_UNWRITTEN;
+ return ret;
+}
+
+/*
+ * work on completed aio dio IO, to convert unwritten extents to extents
+ */
+static void ext4_end_io_work(struct work_struct *work)
+{
+ ext4_io_end_t *io = container_of(work, ext4_io_end_t, work);
+ struct inode *inode = io->inode;
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ unsigned long flags;
+ int ret;
+
+ mutex_lock(&inode->i_mutex);
+ ret = ext4_end_io_nolock(io);
+ if (ret < 0) {
+ mutex_unlock(&inode->i_mutex);
+ return;
+ }
+
+ spin_lock_irqsave(&ei->i_completed_io_lock, flags);
+ if (!list_empty(&io->list))
+ list_del_init(&io->list);
+ spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
+ mutex_unlock(&inode->i_mutex);
+ ext4_free_io_end(io);
+}
+
+ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
+{
+ ext4_io_end_t *io = NULL;
+
+ io = kmem_cache_alloc(io_end_cachep, flags);
+ if (io) {
+ memset(io, 0, sizeof(*io));
+ io->inode = igrab(inode);
+ BUG_ON(!io->inode);
+ INIT_WORK(&io->work, ext4_end_io_work);
+ INIT_LIST_HEAD(&io->list);
+ }
+ return io;
+}
+
+/*
+ * Print an buffer I/O error compatible with the fs/buffer.c. This
+ * provides compatibility with dmesg scrapers that look for a specific
+ * buffer I/O error message. We really need a unified error reporting
+ * structure to userspace ala Digital Unix's uerf system, but it's
+ * probably not going to happen in my lifetime, due to LKML politics...
+ */
+static void buffer_io_error(struct buffer_head *bh)
+{
+ char b[BDEVNAME_SIZE];
+ printk(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
+ bdevname(bh->b_bdev, b),
+ (unsigned long long)bh->b_blocknr);
+}
+
+static void ext4_end_bio(struct bio *bio, int error)
+{
+ ext4_io_end_t *io_end = bio->bi_private;
+ struct workqueue_struct *wq;
+ struct inode *inode;
+ unsigned long flags;
+ ext4_fsblk_t err_block;
+ int i;
+
+ BUG_ON(!io_end);
+ inode = io_end->inode;
+ bio->bi_private = NULL;
+ bio->bi_end_io = NULL;
+ if (test_bit(BIO_UPTODATE, &bio->bi_flags))
+ error = 0;
+ err_block = bio->bi_sector >> (inode->i_blkbits - 9);
+ bio_put(bio);
+
+ if (!(inode->i_sb->s_flags & MS_ACTIVE)) {
+ pr_err("sb umounted, discard end_io request for inode %lu\n",
+ io_end->inode->i_ino);
+ ext4_free_io_end(io_end);
+ return;
+ }
+
+ if (error) {
+ io_end->flag |= EXT4_IO_END_ERROR;
+ ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
+ "(offset %llu size %ld starting block %llu)",
+ inode->i_ino,
+ (unsigned long long) io_end->offset,
+ (long) io_end->size,
+ (unsigned long long) err_block);
+ }
+
+ for (i = 0; i < io_end->num_io_pages; i++) {
+ struct page *page = io_end->pages[i]->p_page;
+ struct buffer_head *bh, *head;
+ int partial_write = 0;
+
+ head = page_buffers(page);
+ if (error)
+ SetPageError(page);
+ BUG_ON(!head);
+ if (head->b_size == PAGE_CACHE_SIZE)
+ clear_buffer_dirty(head);
+ else {
+ loff_t offset;
+ loff_t io_end_offset = io_end->offset + io_end->size;
+
+ offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
+ bh = head;
+ do {
+ if ((offset >= io_end->offset) &&
+ (offset+bh->b_size <= io_end_offset)) {
+ if (error)
+ buffer_io_error(bh);
+
+ clear_buffer_dirty(bh);
+ }
+ if (buffer_delay(bh))
+ partial_write = 1;
+ else if (!buffer_mapped(bh))
+ clear_buffer_dirty(bh);
+ else if (buffer_dirty(bh))
+ partial_write = 1;
+ offset += bh->b_size;
+ bh = bh->b_this_page;
+ } while (bh != head);
+ }
+
+ if (--io_end->pages[i]->p_count == 0) {
+ struct page *page = io_end->pages[i]->p_page;
+
+ end_page_writeback(page);
+ put_page(page);
+ kmem_cache_free(io_page_cachep, io_end->pages[i]);
+ }
+
+ /*
+ * If this is a partial write which happened to make
+ * all buffers uptodate then we can optimize away a
+ * bogus readpage() for the next read(). Here we
+ * 'discover' whether the page went uptodate as a
+ * result of this (potentially partial) write.
+ */
+ if (!partial_write)
+ SetPageUptodate(page);
+ }
+
+ io_end->num_io_pages = 0;
+
+ /* Add the io_end to per-inode completed io list*/
+ spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
+ list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
+ spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
+
+ wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
+ /* queue the work to convert unwritten extents to written */
+ queue_work(wq, &io_end->work);
+}
+
+void ext4_io_submit(struct ext4_io_submit *io)
+{
+ struct bio *bio = io->io_bio;
+
+ if (bio) {
+ bio_get(io->io_bio);
+ submit_bio(io->io_op, io->io_bio);
+ BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
+ bio_put(io->io_bio);
+ }
+ io->io_bio = 0;
+ io->io_op = 0;
+ io->io_end = 0;
+}
+
+static int io_submit_init(struct ext4_io_submit *io,
+ struct inode *inode,
+ struct writeback_control *wbc,
+ 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;
+ do {
+ bio = bio_alloc(GFP_NOIO, nvecs);
+ nvecs >>= 1;
+ } while (bio == NULL);
+
+ 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->inode = inode;
+ io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
+
+ io->io_bio = bio;
+ io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?
+ WRITE_SYNC_PLUG : WRITE);
+ io->io_next_block = bh->b_blocknr;
+ return 0;
+}
+
+static int io_submit_add_bh(struct ext4_io_submit *io,
+ struct ext4_io_page *io_page,
+ struct inode *inode,
+ struct writeback_control *wbc,
+ struct buffer_head *bh)
+{
+ ext4_io_end_t *io_end;
+ int ret;
+
+ if (buffer_new(bh)) {
+ clear_buffer_new(bh);
+ unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
+ }
+
+ if (!buffer_mapped(bh) || buffer_delay(bh)) {
+ if (!buffer_mapped(bh))
+ clear_buffer_dirty(bh);
+ if (io->io_bio)
+ ext4_io_submit(io);
+ return 0;
+ }
+
+ if (io->io_bio && bh->b_blocknr != io->io_next_block) {
+submit_and_retry:
+ ext4_io_submit(io);
+ }
+ if (io->io_bio == NULL) {
+ ret = io_submit_init(io, inode, wbc, bh);
+ if (ret)
+ return ret;
+ }
+ io_end = io->io_end;
+ if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
+ (io_end->pages[io_end->num_io_pages-1] != io_page))
+ goto submit_and_retry;
+ if (buffer_uninit(bh))
+ io->io_end->flag |= EXT4_IO_END_UNWRITTEN;
+ io->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;
+ if ((io_end->num_io_pages == 0) ||
+ (io_end->pages[io_end->num_io_pages-1] != io_page)) {
+ io_end->pages[io_end->num_io_pages++] = io_page;
+ io_page->p_count++;
+ }
+ return 0;
+}
+
+int ext4_bio_write_page(struct ext4_io_submit *io,
+ struct page *page,
+ int len,
+ struct writeback_control *wbc)
+{
+ struct inode *inode = page->mapping->host;
+ unsigned block_start, block_end, blocksize;
+ struct ext4_io_page *io_page;
+ struct buffer_head *bh, *head;
+ int ret = 0;
+
+ blocksize = 1 << inode->i_blkbits;
+
+ BUG_ON(PageWriteback(page));
+ set_page_writeback(page);
+ ClearPageError(page);
+
+ io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
+ if (!io_page) {
+ set_page_dirty(page);
+ unlock_page(page);
+ return -ENOMEM;
+ }
+ io_page->p_page = page;
+ io_page->p_count = 0;
+ get_page(page);
+
+ for (bh = head = page_buffers(page), block_start = 0;
+ bh != head || !block_start;
+ block_start = block_end, bh = bh->b_this_page) {
+ block_end = block_start + blocksize;
+ if (block_start >= len) {
+ clear_buffer_dirty(bh);
+ set_buffer_uptodate(bh);
+ continue;
+ }
+ ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
+ if (ret) {
+ /*
+ * We only get here on ENOMEM. Not much else
+ * we can do but mark the page as dirty, and
+ * better luck next time.
+ */
+ set_page_dirty(page);
+ break;
+ }
+ }
+ unlock_page(page);
+ /*
+ * If the page was truncated before we could do the writeback,
+ * or we had a memory allocation error while trying to write
+ * the first buffer head, we won't have submitted any pages for
+ * I/O. In that case we need to make sure we've cleared the
+ * PageWriteback bit from the page to prevent the system from
+ * wedging later on.
+ */
+ if (io_page->p_count == 0) {
+ put_page(page);
+ end_page_writeback(page);
+ kmem_cache_free(io_page_cachep, io_page);
+ }
+ return ret;
+}