ext4: use bio layer instead of buffer layer in mpage_da_submit_io
Theodore Ts'o [Thu, 28 Oct 2010 01:30:10 +0000 (21:30 -0400)]
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>

fs/ext4/Makefile
fs/ext4/ext4.h
fs/ext4/extents.c
fs/ext4/inode.c
fs/ext4/page-io.c [new file with mode: 0644]
fs/ext4/super.c

index 8867b2a..c947e36 100644 (file)
@@ -4,7 +4,7 @@
 
 obj-$(CONFIG_EXT4_FS) += ext4.o
 
-ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
+ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
                ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
                ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o
 
index 2283369..ca9fda6 100644 (file)
@@ -168,7 +168,20 @@ struct mpage_da_data {
        int pages_written;
        int retval;
 };
-#define        EXT4_IO_UNWRITTEN       0x1
+
+/*
+ * Flags for ext4_io_end->flags
+ */
+#define        EXT4_IO_END_UNWRITTEN   0x0001
+#define EXT4_IO_END_ERROR      0x0002
+
+struct ext4_io_page {
+       struct page     *p_page;
+       int             p_count;
+};
+
+#define MAX_IO_PAGES 128
+
 typedef struct ext4_io_end {
        struct list_head        list;           /* per-file finished IO list */
        struct inode            *inode;         /* file being written to */
@@ -179,8 +192,18 @@ typedef struct ext4_io_end {
        struct work_struct      work;           /* data work queue */
        struct kiocb            *iocb;          /* iocb struct for AIO */
        int                     result;         /* error value for AIO */
+       int                     num_io_pages;
+       struct ext4_io_page     *pages[MAX_IO_PAGES];
 } ext4_io_end_t;
 
+struct ext4_io_submit {
+       int                     io_op;
+       struct bio              *io_bio;
+       ext4_io_end_t           *io_end;
+       struct ext4_io_page     *io_page;
+       sector_t                io_next_block;
+};
+
 /*
  * Special inodes numbers
  */
@@ -2044,6 +2067,17 @@ extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
                             __u64 start_orig, __u64 start_donor,
                             __u64 len, __u64 *moved_len);
 
+/* page-io.c */
+extern int __init init_ext4_pageio(void);
+extern void exit_ext4_pageio(void);
+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 int ext4_end_io_nolock(ext4_io_end_t *io);
+extern void ext4_io_submit(struct ext4_io_submit *io);
+extern int ext4_bio_write_page(struct ext4_io_submit *io,
+                              struct page *page,
+                              int len,
+                              struct writeback_control *wbc);
 
 /* BH_Uninit flag: blocks are allocated but uninitialized on disk */
 enum ext4_state_bits {
index a0e6230..a1e20c8 100644 (file)
@@ -3202,7 +3202,7 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
                 * completed
                 */
                if (io)
-                       io->flag = EXT4_IO_UNWRITTEN;
+                       io->flag = EXT4_IO_END_UNWRITTEN;
                else
                        ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
                if (ext4_should_dioread_nolock(inode))
@@ -3494,7 +3494,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
                 */
                if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
                        if (io)
-                               io->flag = EXT4_IO_UNWRITTEN;
+                               io->flag = EXT4_IO_END_UNWRITTEN;
                        else
                                ext4_set_inode_state(inode,
                                                     EXT4_STATE_DIO_UNWRITTEN);
index c65d647..58604fe 100644 (file)
@@ -2016,8 +2016,10 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
        struct buffer_head *bh, *page_bufs = NULL;
        int journal_data = ext4_should_journal_data(inode);
        sector_t pblock = 0, cur_logical = 0;
+       struct ext4_io_submit io_submit;
 
        BUG_ON(mpd->next_page <= mpd->first_page);
+       memset(&io_submit, 0, sizeof(io_submit));
        /*
         * We need to start from the first_page to the next_page - 1
         * to make sure we also write the mapped dirty buffer_heads.
@@ -2109,16 +2111,16 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
                                /* mark the buffer_heads as dirty & uptodate */
                                block_commit_write(page, 0, len);
 
-                       if (journal_data && PageChecked(page))
+                       /*
+                        * Delalloc doesn't support data journalling,
+                        * but eventually maybe we'll lift this
+                        * restriction.
+                        */
+                       if (unlikely(journal_data && PageChecked(page)))
                                err = __ext4_journalled_writepage(page, len);
-                       else if (buffer_uninit(page_bufs)) {
-                               ext4_set_bh_endio(page_bufs, inode);
-                               err = block_write_full_page_endio(page,
-                                       noalloc_get_block_write,
-                                       mpd->wbc, ext4_end_io_buffer_write);
-                       } else
-                               err = block_write_full_page(page,
-                                           noalloc_get_block_write, mpd->wbc);
+                       else
+                               err = ext4_bio_write_page(&io_submit, page,
+                                                         len, mpd->wbc);
 
                        if (!err)
                                mpd->pages_written++;
@@ -2131,6 +2133,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
                }
                pagevec_release(&pvec);
        }
+       ext4_io_submit(&io_submit);
        return ret;
 }
 
@@ -3426,15 +3429,6 @@ ext4_readpages(struct file *file, struct address_space *mapping,
        return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
 }
 
-static void ext4_free_io_end(ext4_io_end_t *io)
-{
-       BUG_ON(!io);
-       if (io->page)
-               put_page(io->page);
-       iput(io->inode);
-       kfree(io);
-}
-
 static void ext4_invalidatepage_free_endio(struct page *page, unsigned long offset)
 {
        struct buffer_head *head, *bh;
@@ -3640,68 +3634,6 @@ static void dump_completed_IO(struct inode * inode)
 }
 
 /*
- * check a range of space and convert unwritten extents to written.
- */
-static 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_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 = 0;
-       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);
-}
-
-/*
  * This function is called from ext4_sync_file().
  *
  * When IO is completed, the work to convert unwritten extents to
@@ -3756,28 +3688,6 @@ int flush_completed_IO(struct inode *inode)
        return (ret2 < 0) ? ret2 : 0;
 }
 
-static ext4_io_end_t *ext4_init_io_end (struct inode *inode, gfp_t flags)
-{
-       ext4_io_end_t *io = NULL;
-
-       io = kmalloc(sizeof(*io), flags);
-
-       if (io) {
-               igrab(inode);
-               io->inode = inode;
-               io->flag = 0;
-               io->offset = 0;
-               io->size = 0;
-               io->page = NULL;
-               io->iocb = NULL;
-               io->result = 0;
-               INIT_WORK(&io->work, ext4_end_io_work);
-               INIT_LIST_HEAD(&io->list);
-       }
-
-       return io;
-}
-
 static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
                            ssize_t size, void *private, int ret,
                            bool is_async)
@@ -3797,7 +3707,7 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
                  size);
 
        /* if not aio dio with unwritten extents, just free io and return */
-       if (io_end->flag != EXT4_IO_UNWRITTEN){
+       if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
                ext4_free_io_end(io_end);
                iocb->private = NULL;
 out:
@@ -3842,7 +3752,7 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate)
                goto out;
        }
 
-       io_end->flag = EXT4_IO_UNWRITTEN;
+       io_end->flag = EXT4_IO_END_UNWRITTEN;
        inode = io_end->inode;
 
        /* Add the io_end to per-inode completed io list*/
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
new file mode 100644 (file)
index 0000000..b972ca5
--- /dev/null
@@ -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;
+}
index 8a24e9b..e13b3c3 100644 (file)
@@ -4769,9 +4769,12 @@ static int __init init_ext4_fs(void)
        int err;
 
        ext4_check_flag_values();
-       err = init_ext4_system_zone();
+       err = init_ext4_pageio();
        if (err)
                return err;
+       err = init_ext4_system_zone();
+       if (err)
+               goto out5;
        ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj);
        if (!ext4_kset)
                goto out4;
@@ -4812,6 +4815,8 @@ out3:
        kset_unregister(ext4_kset);
 out4:
        exit_ext4_system_zone();
+out5:
+       exit_ext4_pageio();
        return err;
 }
 
@@ -4827,6 +4832,7 @@ static void __exit exit_ext4_fs(void)
        remove_proc_entry("fs/ext4", NULL);
        kset_unregister(ext4_kset);
        exit_ext4_system_zone();
+       exit_ext4_pageio();
 }
 
 MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");