ocfs2: teach ocfs2_file_aio_write() about sparse files

Unfortunately, ocfs2 can no longer make use of generic_file_aio_write_nlock()
because allocating writes will require zeroing of pages adjacent to the I/O
for cluster sizes greater than page size.

Implement a custom file write here, which can order page locks for zeroing.
This also has the advantage that cluster locks can easily be ordered outside
of the page locks.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

7 files changed, 1076 insertions, 57 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f3b0cc5cba1a..5ffb3702b5e9 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -24,6 +24,7 @@
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <asm/byteorder.h>
+#include <linux/swap.h>
 
 #define MLOG_MASK_PREFIX ML_FILE_IO
 #include <cluster/masklog.h>
@@ -37,6 +38,7 @@
 #include "file.h"
 #include "inode.h"
 #include "journal.h"
+#include "suballoc.h"
 #include "super.h"
 #include "symlink.h"
 
@@ -645,23 +647,27 @@ static ssize_t ocfs2_direct_IO(int rw,
 
         mlog_entry_void();
 
-        /*
-         * We get PR data locks even for O_DIRECT.  This allows
-         * concurrent O_DIRECT I/O but doesn't let O_DIRECT with
-         * extending and buffered zeroing writes race.  If they did
-         * race then the buffered zeroing could be written back after
-         * the O_DIRECT I/O.  It's one thing to tell people not to mix
-         * buffered and O_DIRECT writes, but expecting them to
-         * understand that file extension is also an implicit buffered
-         * write is too much.  By getting the PR we force writeback of
-         * the buffered zeroing before proceeding.
-         */
-        ret = ocfs2_data_lock(inode, 0);
-        if (ret < 0) {
-                mlog_errno(ret);
-                goto out;
+        if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+                /*
+                 * We get PR data locks even for O_DIRECT.  This
+                 * allows concurrent O_DIRECT I/O but doesn't let
+                 * O_DIRECT with extending and buffered zeroing writes
+                 * race.  If they did race then the buffered zeroing
+                 * could be written back after the O_DIRECT I/O.  It's
+                 * one thing to tell people not to mix buffered and
+                 * O_DIRECT writes, but expecting them to understand
+                 * that file extension is also an implicit buffered
+                 * write is too much.  By getting the PR we force
+                 * writeback of the buffered zeroing before
+                 * proceeding.
+                 */
+                ret = ocfs2_data_lock(inode, 0);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+                ocfs2_data_unlock(inode, 0);
         }
-        ocfs2_data_unlock(inode, 0);
 
         ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
                                             inode->i_sb->s_bdev, iov, offset,
@@ -673,6 +679,647 @@ out:
         return ret;
 }
 
+static void ocfs2_figure_cluster_boundaries(struct ocfs2_super *osb,
+                                            u32 cpos,
+                                            unsigned int *start,
+                                            unsigned int *end)
+{
+        unsigned int cluster_start = 0, cluster_end = PAGE_CACHE_SIZE;
+
+        if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits)) {
+                unsigned int cpp;
+
+                cpp = 1 << (PAGE_CACHE_SHIFT - osb->s_clustersize_bits);
+
+                cluster_start = cpos % cpp;
+                cluster_start = cluster_start << osb->s_clustersize_bits;
+
+                cluster_end = cluster_start + osb->s_clustersize;
+        }
+
+        BUG_ON(cluster_start > PAGE_SIZE);
+        BUG_ON(cluster_end > PAGE_SIZE);
+
+        if (start)
+                *start = cluster_start;
+        if (end)
+                *end = cluster_end;
+}
+
+/*
+ * 'from' and 'to' are the region in the page to avoid zeroing.
+ *
+ * If pagesize > clustersize, this function will avoid zeroing outside
+ * of the cluster boundary.
+ *
+ * from == to == 0 is code for "zero the entire cluster region"
+ */
+static void ocfs2_clear_page_regions(struct page *page,
+                                     struct ocfs2_super *osb, u32 cpos,
+                                     unsigned from, unsigned to)
+{
+        void *kaddr;
+        unsigned int cluster_start, cluster_end;
+
+        ocfs2_figure_cluster_boundaries(osb, cpos, &cluster_start, &cluster_end);
+
+        kaddr = kmap_atomic(page, KM_USER0);
+
+        if (from || to) {
+                if (from > cluster_start)
+                        memset(kaddr + cluster_start, 0, from - cluster_start);
+                if (to < cluster_end)
+                        memset(kaddr + to, 0, cluster_end - to);
+        } else {
+                memset(kaddr + cluster_start, 0, cluster_end - cluster_start);
+        }
+
+        kunmap_atomic(kaddr, KM_USER0);
+}
+
+/*
+ * Some of this taken from block_prepare_write(). We already have our
+ * mapping by now though, and the entire write will be allocating or
+ * it won't, so not much need to use BH_New.
+ *
+ * This will also skip zeroing, which is handled externally.
+ */
+static int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
+                                 struct inode *inode, unsigned int from,
+                                 unsigned int to, int new)
+{
+        int ret = 0;
+        struct buffer_head *head, *bh, *wait[2], **wait_bh = wait;
+        unsigned int block_end, block_start;
+        unsigned int bsize = 1 << inode->i_blkbits;
+
+        if (!page_has_buffers(page))
+                create_empty_buffers(page, bsize, 0);
+
+        head = page_buffers(page);
+        for (bh = head, block_start = 0; bh != head || !block_start;
+             bh = bh->b_this_page, block_start += bsize) {
+                block_end = block_start + bsize;
+
+                /*
+                 * Ignore blocks outside of our i/o range -
+                 * they may belong to unallocated clusters.
+                 */
+                if (block_start >= to ||
+                    (block_start + bsize) <= from) {
+                        if (PageUptodate(page))
+                                set_buffer_uptodate(bh);
+                        continue;
+                }
+
+                /*
+                 * For an allocating write with cluster size >= page
+                 * size, we always write the entire page.
+                 */
+
+                if (buffer_new(bh))
+                        clear_buffer_new(bh);
+
+                if (!buffer_mapped(bh)) {
+                        map_bh(bh, inode->i_sb, *p_blkno);
+                        unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
+                }
+
+                if (PageUptodate(page)) {
+                        if (!buffer_uptodate(bh))
+                                set_buffer_uptodate(bh);
+                } else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
+                     (block_start < from || block_end > to)) {
+                        ll_rw_block(READ, 1, &bh);
+                        *wait_bh++=bh;
+                }
+
+                *p_blkno = *p_blkno + 1;
+        }
+
+        /*
+         * If we issued read requests - let them complete.
+         */
+        while(wait_bh > wait) {
+                wait_on_buffer(*--wait_bh);
+                if (!buffer_uptodate(*wait_bh))
+                        ret = -EIO;
+        }
+
+        if (ret == 0 || !new)
+                return ret;
+
+        /*
+         * If we get -EIO above, zero out any newly allocated blocks
+         * to avoid exposing stale data.
+         */
+        bh = head;
+        block_start = 0;
+        do {
+                void *kaddr;
+
+                block_end = block_start + bsize;
+                if (block_end <= from)
+                        goto next_bh;
+                if (block_start >= to)
+                        break;
+
+                kaddr = kmap_atomic(page, KM_USER0);
+                memset(kaddr+block_start, 0, bh->b_size);
+                flush_dcache_page(page);
+                kunmap_atomic(kaddr, KM_USER0);
+                set_buffer_uptodate(bh);
+                mark_buffer_dirty(bh);
+
+next_bh:
+                block_start = block_end;
+                bh = bh->b_this_page;
+        } while (bh != head);
+
+        return ret;
+}
+
+/*
+ * This will copy user data from the iovec in the buffered write
+ * context.
+ */
+int ocfs2_map_and_write_user_data(struct inode *inode,
+                                  struct ocfs2_write_ctxt *wc, u64 *p_blkno,
+                                  unsigned int *ret_from, unsigned int *ret_to)
+{
+        int ret;
+        unsigned int to, from, cluster_start, cluster_end;
+        unsigned long bytes, src_from;
+        char *dst;
+        struct ocfs2_buffered_write_priv *bp = wc->w_private;
+        const struct iovec *cur_iov = bp->b_cur_iov;
+        char __user *buf;
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+        ocfs2_figure_cluster_boundaries(osb, wc->w_cpos, &cluster_start,
+                                        &cluster_end);
+
+        buf = cur_iov->iov_base + bp->b_cur_off;
+        src_from = (unsigned long)buf & ~PAGE_CACHE_MASK;
+
+        from = wc->w_pos & (PAGE_CACHE_SIZE - 1);
+
+        /*
+         * This is a lot of comparisons, but it reads quite
+         * easily, which is important here.
+         */
+        /* Stay within the src page */
+        bytes = PAGE_SIZE - src_from;
+        /* Stay within the vector */
+        bytes = min(bytes,
+                    (unsigned long)(cur_iov->iov_len - bp->b_cur_off));
+        /* Stay within count */
+        bytes = min(bytes, (unsigned long)wc->w_count);
+        /*
+         * For clustersize > page size, just stay within
+         * target page, otherwise we have to calculate pos
+         * within the cluster and obey the rightmost
+         * boundary.
+         */
+        if (wc->w_large_pages) {
+                /*
+                 * For cluster size < page size, we have to
+                 * calculate pos within the cluster and obey
+                 * the rightmost boundary.
+                 */
+                bytes = min(bytes, (unsigned long)(osb->s_clustersize
+                                   - (wc->w_pos & (osb->s_clustersize - 1))));
+        } else {
+                /*
+                 * cluster size > page size is the most common
+                 * case - we just stay within the target page
+                 * boundary.
+                 */
+                bytes = min(bytes, PAGE_CACHE_SIZE - from);
+        }
+
+        to = from + bytes;
+
+        if (wc->w_this_page_new)
+                ret = ocfs2_map_page_blocks(wc->w_this_page, p_blkno, inode,
+                                            cluster_start, cluster_end, 1);
+        else
+                ret = ocfs2_map_page_blocks(wc->w_this_page, p_blkno, inode,
+                                            from, to, 0);
+        if (ret) {
+                mlog_errno(ret);
+                goto out;
+        }
+
+        BUG_ON(from > PAGE_CACHE_SIZE);
+        BUG_ON(to > PAGE_CACHE_SIZE);
+        BUG_ON(from > osb->s_clustersize);
+        BUG_ON(to > osb->s_clustersize);
+
+        dst = kmap(wc->w_this_page);
+        memcpy(dst + from, bp->b_src_buf + src_from, bytes);
+        kunmap(wc->w_this_page);
+
+        /*
+         * XXX: This is slow, but simple. The caller of
+         * ocfs2_buffered_write_cluster() is responsible for
+         * passing through the iovecs, so it's difficult to
+         * predict what our next step is in here after our
+         * initial write. A future version should be pushing
+         * that iovec manipulation further down.
+         *
+         * By setting this, we indicate that a copy from user
+         * data was done, and subsequent calls for this
+         * cluster will skip copying more data.
+         */
+        wc->w_finished_copy = 1;
+
+        *ret_from = from;
+        *ret_to = to;
+out:
+
+        return bytes ? (unsigned int)bytes : ret;
+}
+
+/*
+ * Map, fill and write a page to disk.
+ *
+ * The work of copying data is done via callback.  Newly allocated
+ * pages which don't take user data will be zero'd (set 'new' to
+ * indicate an allocating write)
+ *
+ * Returns a negative error code or the number of bytes copied into
+ * the page.
+ */
+int ocfs2_write_data_page(struct inode *inode, handle_t *handle,
+                          u64 *p_blkno, struct page *page,
+                          struct ocfs2_write_ctxt *wc, int new)
+{
+        int ret, copied = 0;
+        unsigned int from = 0, to = 0;
+        unsigned int cluster_start, cluster_end;
+        unsigned int zero_from = 0, zero_to = 0;
+
+        ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), wc->w_cpos,
+                                        &cluster_start, &cluster_end);
+
+        if ((wc->w_pos >> PAGE_CACHE_SHIFT) == page->index
+            && !wc->w_finished_copy) {
+
+                wc->w_this_page = page;
+                wc->w_this_page_new = new;
+                ret = wc->w_write_data_page(inode, wc, p_blkno, &from, &to);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+
+                copied = ret;
+
+                zero_from = from;
+                zero_to = to;
+                if (new) {
+                        from = cluster_start;
+                        to = cluster_end;
+                }
+        } else {
+                /*
+                 * If we haven't allocated the new page yet, we
+                 * shouldn't be writing it out without copying user
+                 * data. This is likely a math error from the caller.
+                 */
+                BUG_ON(!new);
+
+                from = cluster_start;
+                to = cluster_end;
+
+                ret = ocfs2_map_page_blocks(page, p_blkno, inode,
+                                            cluster_start, cluster_end, 1);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+        }
+
+        /*
+         * Parts of newly allocated pages need to be zero'd.
+         *
+         * Above, we have also rewritten 'to' and 'from' - as far as
+         * the rest of the function is concerned, the entire cluster
+         * range inside of a page needs to be written.
+         *
+         * We can skip this if the page is up to date - it's already
+         * been zero'd from being read in as a hole.
+         */
+        if (new && !PageUptodate(page))
+                ocfs2_clear_page_regions(page, OCFS2_SB(inode->i_sb),
+                                         wc->w_cpos, zero_from, zero_to);
+
+        flush_dcache_page(page);
+
+        if (ocfs2_should_order_data(inode)) {
+                ret = walk_page_buffers(handle,
+                                        page_buffers(page),
+                                        from, to, NULL,
+                                        ocfs2_journal_dirty_data);
+                if (ret < 0)
+                        mlog_errno(ret);
+        }
+
+        /*
+         * We don't use generic_commit_write() because we need to
+         * handle our own i_size update.
+         */
+        ret = block_commit_write(page, from, to);
+        if (ret)
+                mlog_errno(ret);
+out:
+
+        return copied ? copied : ret;
+}
+
+/*
+ * Do the actual write of some data into an inode. Optionally allocate
+ * in order to fulfill the write.
+ *
+ * cpos is the logical cluster offset within the file to write at
+ *
+ * 'phys' is the physical mapping of that offset. a 'phys' value of
+ * zero indicates that allocation is required. In this case, data_ac
+ * and meta_ac should be valid (meta_ac can be null if metadata
+ * allocation isn't required).
+ */
+static ssize_t ocfs2_write(struct file *file, u32 phys, handle_t *handle,
+                           struct buffer_head *di_bh,
+                           struct ocfs2_alloc_context *data_ac,
+                           struct ocfs2_alloc_context *meta_ac,
+                           struct ocfs2_write_ctxt *wc)
+{
+        int ret, i, numpages = 1, new;
+        unsigned int copied = 0;
+        u32 tmp_pos;
+        u64 v_blkno, p_blkno;
+        struct address_space *mapping = file->f_mapping;
+        struct inode *inode = mapping->host;
+        unsigned int cbits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+        unsigned long index, start;
+        struct page **cpages;
+
+        new = phys == 0 ? 1 : 0;
+
+        /*
+         * Figure out how many pages we'll be manipulating here. For
+         * non-allocating write, or any writes where cluster size is
+         * less than page size, we only need one page. Otherwise,
+         * allocating writes of cluster size larger than page size
+         * need cluster size pages.
+         */
+        if (new && !wc->w_large_pages)
+                numpages = (1 << cbits) / PAGE_SIZE;
+
+        cpages = kzalloc(sizeof(*cpages) * numpages, GFP_NOFS);
+        if (!cpages) {
+                ret = -ENOMEM;
+                mlog_errno(ret);
+                return ret;
+        }
+
+        /*
+         * Fill our page array first. That way we've grabbed enough so
+         * that we can zero and flush if we error after adding the
+         * extent.
+         */
+        if (new) {
+                start = ocfs2_align_clusters_to_page_index(inode->i_sb,
+                                                           wc->w_cpos);
+                v_blkno = ocfs2_clusters_to_blocks(inode->i_sb, wc->w_cpos);
+        } else {
+                start = wc->w_pos >> PAGE_CACHE_SHIFT;
+                v_blkno = wc->w_pos >> inode->i_sb->s_blocksize_bits;
+        }
+
+        for(i = 0; i < numpages; i++) {
+                index = start + i;
+
+                cpages[i] = grab_cache_page(mapping, index);
+                if (!cpages[i]) {
+                        ret = -ENOMEM;
+                        mlog_errno(ret);
+                        goto out;
+                }
+        }
+
+        if (new) {
+                /*
+                 * This is safe to call with the page locks - it won't take
+                 * any additional semaphores or cluster locks.
+                 */
+                tmp_pos = wc->w_cpos;
+                ret = ocfs2_do_extend_allocation(OCFS2_SB(inode->i_sb), inode,
+                                                 &tmp_pos, 1, di_bh, handle,
+                                                 data_ac, meta_ac, NULL);
+                /*
+                 * This shouldn't happen because we must have already
+                 * calculated the correct meta data allocation required. The
+                 * internal tree allocation code should know how to increase
+                 * transaction credits itself.
+                 *
+                 * If need be, we could handle -EAGAIN for a
+                 * RESTART_TRANS here.
+                 */
+                mlog_bug_on_msg(ret == -EAGAIN,
+                                "Inode %llu: EAGAIN return during allocation.\n",
+                                (unsigned long long)OCFS2_I(inode)->ip_blkno);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+        }
+
+        ret = ocfs2_extent_map_get_blocks(inode, v_blkno, &p_blkno, NULL);
+        if (ret < 0) {
+
+                /*
+                 * XXX: Should we go readonly here?
+                 */
+
+                mlog_errno(ret);
+                goto out;
+        }
+
+        BUG_ON(p_blkno == 0);
+
+        for(i = 0; i < numpages; i++) {
+                ret = ocfs2_write_data_page(inode, handle, &p_blkno, cpages[i],
+                                            wc, new);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+
+                copied += ret;
+        }
+
+out:
+        for(i = 0; i < numpages; i++) {
+                unlock_page(cpages[i]);
+                mark_page_accessed(cpages[i]);
+                page_cache_release(cpages[i]);
+        }
+        kfree(cpages);
+
+        return copied ? copied : ret;
+}
+
+static void ocfs2_write_ctxt_init(struct ocfs2_write_ctxt *wc,
+                                  struct ocfs2_super *osb, loff_t pos,
+                                  size_t count, ocfs2_page_writer *cb,
+                                  void *cb_priv)
+{
+        wc->w_count = count;
+        wc->w_pos = pos;
+        wc->w_cpos = wc->w_pos >> osb->s_clustersize_bits;
+        wc->w_finished_copy = 0;
+
+        if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits))
+                wc->w_large_pages = 1;
+        else
+                wc->w_large_pages = 0;
+
+        wc->w_write_data_page = cb;
+        wc->w_private = cb_priv;
+}
+
+/*
+ * Write a cluster to an inode. The cluster may not be allocated yet,
+ * in which case it will be. This only exists for buffered writes -
+ * O_DIRECT takes a more "traditional" path through the kernel.
+ *
+ * The caller is responsible for incrementing pos, written counts, etc
+ *
+ * For file systems that don't support sparse files, pre-allocation
+ * and page zeroing up until cpos should be done prior to this
+ * function call.
+ *
+ * Callers should be holding i_sem, and the rw cluster lock.
+ *
+ * Returns the number of user bytes written, or less than zero for
+ * error.
+ */
+ssize_t ocfs2_buffered_write_cluster(struct file *file, loff_t pos,
+                                     size_t count, ocfs2_page_writer *actor,
+                                     void *priv)
+{
+        int ret, credits = OCFS2_INODE_UPDATE_CREDITS;
+        ssize_t written = 0;
+        u32 phys;
+        struct inode *inode = file->f_mapping->host;
+        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+        struct buffer_head *di_bh = NULL;
+        struct ocfs2_dinode *di;
+        struct ocfs2_alloc_context *data_ac = NULL;
+        struct ocfs2_alloc_context *meta_ac = NULL;
+        handle_t *handle;
+        struct ocfs2_write_ctxt wc;
+
+        ocfs2_write_ctxt_init(&wc, osb, pos, count, actor, priv);
+
+        ret = ocfs2_meta_lock(inode, &di_bh, 1);
+        if (ret) {
+                mlog_errno(ret);
+                goto out;
+        }
+        di = (struct ocfs2_dinode *)di_bh->b_data;
+
+        /*
+         * Take alloc sem here to prevent concurrent lookups. That way
+         * the mapping, zeroing and tree manipulation within
+         * ocfs2_write() will be safe against ->readpage(). This
+         * should also serve to lock out allocation from a shared
+         * writeable region.
+         */
+        down_write(&OCFS2_I(inode)->ip_alloc_sem);
+
+        ret = ocfs2_get_clusters(inode, wc.w_cpos, &phys, NULL);
+        if (ret) {
+                mlog_errno(ret);
+                goto out_meta;
+        }
+
+        /* phys == 0 means that allocation is required. */
+        if (phys == 0) {
+                ret = ocfs2_lock_allocators(inode, di, 1, &data_ac, &meta_ac);
+                if (ret) {
+                        mlog_errno(ret);
+                        goto out_meta;
+                }
+
+                credits = ocfs2_calc_extend_credits(inode->i_sb, di, 1);
+        }
+
+        ret = ocfs2_data_lock(inode, 1);
+        if (ret) {
+                mlog_errno(ret);
+                goto out_meta;
+        }
+
+        handle = ocfs2_start_trans(osb, credits);
+        if (IS_ERR(handle)) {
+                ret = PTR_ERR(handle);
+                mlog_errno(ret);
+                goto out_data;
+        }
+
+        written = ocfs2_write(file, phys, handle, di_bh, data_ac,
+                              meta_ac, &wc);
+        if (written < 0) {
+                ret = written;
+                mlog_errno(ret);
+                goto out_commit;
+        }
+
+        ret = ocfs2_journal_access(handle, inode, di_bh,
+                                   OCFS2_JOURNAL_ACCESS_WRITE);
+        if (ret) {
+                mlog_errno(ret);
+                goto out_commit;
+        }
+
+        pos += written;
+        if (pos > inode->i_size) {
+                i_size_write(inode, pos);
+                mark_inode_dirty(inode);
+        }
+        inode->i_blocks = ocfs2_align_bytes_to_sectors((u64)(i_size_read(inode)));
+        di->i_size = cpu_to_le64((u64)i_size_read(inode));
+        inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+        di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
+        di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
+
+        ret = ocfs2_journal_dirty(handle, di_bh);
+        if (ret)
+                mlog_errno(ret);
+
+out_commit:
+        ocfs2_commit_trans(osb, handle);
+
+out_data:
+        ocfs2_data_unlock(inode, 1);
+
+out_meta:
+        up_write(&OCFS2_I(inode)->ip_alloc_sem);
+        ocfs2_meta_unlock(inode, 1);
+
+out:
+        brelse(di_bh);
+        if (data_ac)
+                ocfs2_free_alloc_context(data_ac);
+        if (meta_ac)
+                ocfs2_free_alloc_context(meta_ac);
+
+        return written ? written : ret;
+}
+
 const struct address_space_operations ocfs2_aops = {
         .readpage       = ocfs2_readpage,
         .writepage      = ocfs2_writepage,
diff --git a/fs/ocfs2/aops.h b/fs/ocfs2/aops.h
index f446a15eab88..eeb2c42483e8 100644
--- a/fs/ocfs2/aops.h
+++ b/fs/ocfs2/aops.h
@@ -30,6 +30,44 @@ handle_t *ocfs2_start_walk_page_trans(struct inode *inode,
                                                          unsigned from,
                                                          unsigned to);
 
+struct ocfs2_write_ctxt;
+typedef int (ocfs2_page_writer)(struct inode *, struct ocfs2_write_ctxt *,
+                                u64 *, unsigned int *, unsigned int *);
+
+ssize_t ocfs2_buffered_write_cluster(struct file *file, loff_t pos,
+                                     size_t count, ocfs2_page_writer *actor,
+                                     void *priv);
+
+struct ocfs2_write_ctxt {
+        size_t                          w_count;
+        loff_t                          w_pos;
+        u32                             w_cpos;
+        unsigned int                    w_finished_copy;
+
+        /* This is true if page_size > cluster_size */
+        unsigned int                    w_large_pages;
+
+        /* Filler callback and private data */
+        ocfs2_page_writer               *w_write_data_page;
+        void                            *w_private;
+
+        /* Only valid for the filler callback */
+        struct page                     *w_this_page;
+        unsigned int                    w_this_page_new;
+};
+
+struct ocfs2_buffered_write_priv {
+        char                            *b_src_buf;
+        const struct iovec              *b_cur_iov; /* Current iovec */
+        size_t                          b_cur_off; /* Offset in the
+                                                    * current iovec */
+};
+int ocfs2_map_and_write_user_data(struct inode *inode,
+                                  struct ocfs2_write_ctxt *wc,
+                                  u64 *p_blkno,
+                                  unsigned int *ret_from,
+                                  unsigned int *ret_to);
+
 /* all ocfs2_dio_end_io()'s fault */
 #define ocfs2_iocb_is_rw_locked(iocb) \
         test_bit(0, (unsigned long *)&iocb->private)
diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 3b4322fd369a..937c2722b753 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -67,8 +67,8 @@ static int ocfs2_search_extent_list(struct ocfs2_extent_list *el,
         return ret;
 }
 
-static int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
-                              u32 *p_cluster, u32 *num_clusters)
+int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
+                       u32 *p_cluster, u32 *num_clusters)
 {
         int ret, i;
         struct buffer_head *di_bh = NULL;
diff --git a/fs/ocfs2/extent_map.h b/fs/ocfs2/extent_map.h
index 036e23251448..625d0ee5e04a 100644
--- a/fs/ocfs2/extent_map.h
+++ b/fs/ocfs2/extent_map.h
@@ -25,6 +25,8 @@
 #ifndef _EXTENT_MAP_H
 #define _EXTENT_MAP_H
 
+int ocfs2_get_clusters(struct inode *inode, u32 v_cluster, u32 *p_cluster,
+                       u32 *num_clusters);
 int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
                                 int *ret_count);
 
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 3bcf3629265e..667e5a869bf5 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -33,6 +33,7 @@
 #include <linux/sched.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/mount.h>
+#include <linux/writeback.h>
 
 #define MLOG_MASK_PREFIX ML_INODE
 #include <cluster/masklog.h>
@@ -485,13 +486,13 @@ leave:
  * accessed, and lock them, reserving the appropriate number of bits.
  *
  * Called from ocfs2_extend_allocation() for file systems which don't
- * support holes, and from ocfs2_prepare_write() for file systems
- * which understand sparse inodes.
+ * support holes, and from ocfs2_write() for file systems which
+ * understand sparse inodes.
  */
-static int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
-                                 u32 clusters_to_add,
-                                 struct ocfs2_alloc_context **data_ac,
-                                 struct ocfs2_alloc_context **meta_ac)
+int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
+                          u32 clusters_to_add,
+                          struct ocfs2_alloc_context **data_ac,
+                          struct ocfs2_alloc_context **meta_ac)
 {
         int ret, num_free_extents;
         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
@@ -518,7 +519,7 @@ static int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
          * a cluster lock (because we ran out of room for another
          * extent) will violate ordering rules.
          *
-         * Most of the time we'll only be seeing this 1 page at a time
+         * Most of the time we'll only be seeing this 1 cluster at a time
          * anyway.
          */
         if (!num_free_extents ||
@@ -596,13 +597,6 @@ static int ocfs2_extend_allocation(struct inode *inode,
 restart_all:
         BUG_ON(le32_to_cpu(fe->i_clusters) != OCFS2_I(inode)->ip_clusters);
 
-        status = ocfs2_lock_allocators(inode, fe, clusters_to_add, &data_ac,
-                                       &meta_ac);
-        if (status) {
-                mlog_errno(status);
-                goto leave;
-        }
-
         /* blocks peope in read/write from reading our allocation
          * until we're done changing it. We depend on i_mutex to block
          * other extend/truncate calls while we're here. Ordering wrt
@@ -610,6 +604,13 @@ restart_all:
         down_write(&OCFS2_I(inode)->ip_alloc_sem);
         drop_alloc_sem = 1;
 
+        status = ocfs2_lock_allocators(inode, fe, clusters_to_add, &data_ac,
+                                       &meta_ac);
+        if (status) {
+                mlog_errno(status);
+                goto leave;
+        }
+
         credits = ocfs2_calc_extend_credits(osb->sb, fe, clusters_to_add);
         handle = ocfs2_start_trans(osb, credits);
         if (IS_ERR(handle)) {
@@ -1088,10 +1089,49 @@ out:
         return ret;
 }
 
+/*
+ * Will look for holes and unwritten extents in the range starting at
+ * pos for count bytes (inclusive).
+ */
+static int ocfs2_check_range_for_holes(struct inode *inode, loff_t pos,
+                                       size_t count)
+{
+        int ret = 0;
+        unsigned int extent_flags;
+        u32 cpos, clusters, extent_len, phys_cpos;
+        struct super_block *sb = inode->i_sb;
+
+        cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
+        clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
+
+        while (clusters) {
+                ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
+                                         &extent_flags);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        goto out;
+                }
+
+                if (phys_cpos == 0 || (extent_flags & OCFS2_EXT_UNWRITTEN)) {
+                        ret = 1;
+                        break;
+                }
+
+                if (extent_len > clusters)
+                        extent_len = clusters;
+
+                clusters -= extent_len;
+                cpos += extent_len;
+        }
+out:
+        return ret;
+}
+
 static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                                          loff_t *ppos,
                                          size_t count,
-                                         int appending)
+                                         int appending,
+                                         int *direct_io)
 {
         int ret = 0, meta_level = appending;
         struct inode *inode = dentry->d_inode;
@@ -1143,12 +1183,47 @@ static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
                         saved_pos = *ppos;
                 }
 
+                if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+                        loff_t end = saved_pos + count;
+
+                        /*
+                         * Skip the O_DIRECT checks if we don't need
+                         * them.
+                         */
+                        if (!direct_io || !(*direct_io))
+                                break;
+
+                        /*
+                         * Allowing concurrent direct writes means
+                         * i_size changes wouldn't be synchronized, so
+                         * one node could wind up truncating another
+                         * nodes writes.
+                         */
+                        if (end > i_size_read(inode)) {
+                                *direct_io = 0;
+                                break;
+                        }
+
+                        /*
+                         * We don't fill holes during direct io, so
+                         * check for them here. If any are found, the
+                         * caller will have to retake some cluster
+                         * locks and initiate the io as buffered.
+                         */
+                        ret = ocfs2_check_range_for_holes(inode, saved_pos,
+                                                          count);
+                        if (ret == 1) {
+                                *direct_io = 0;
+                                ret = 0;
+                        } else if (ret < 0)
+                                mlog_errno(ret);
+                        break;
+                }
+
                 /*
                  * The rest of this loop is concerned with legacy file
                  * systems which don't support sparse files.
                  */
-                if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
-                        break;
 
                 newsize = count + saved_pos;
 
@@ -1202,55 +1277,264 @@ out:
         return ret;
 }
 
+static inline void
+ocfs2_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
+{
+        const struct iovec *iov = *iovp;
+        size_t base = *basep;
+
+        do {
+                int copy = min(bytes, iov->iov_len - base);
+
+                bytes -= copy;
+                base += copy;
+                if (iov->iov_len == base) {
+                        iov++;
+                        base = 0;
+                }
+        } while (bytes);
+        *iovp = iov;
+        *basep = base;
+}
+
+static struct page * ocfs2_get_write_source(struct ocfs2_buffered_write_priv *bp,
+                                            const struct iovec *cur_iov,
+                                            size_t iov_offset)
+{
+        int ret;
+        char *buf;
+        struct page *src_page = NULL;
+
+        buf = cur_iov->iov_base + iov_offset;
+
+        if (!segment_eq(get_fs(), KERNEL_DS)) {
+                /*
+                 * Pull in the user page. We want to do this outside
+                 * of the meta data locks in order to preserve locking
+                 * order in case of page fault.
+                 */
+                ret = get_user_pages(current, current->mm,
+                                     (unsigned long)buf & PAGE_CACHE_MASK, 1,
+                                     0, 0, &src_page, NULL);
+                if (ret == 1)
+                        bp->b_src_buf = kmap(src_page);
+                else
+                        src_page = ERR_PTR(-EFAULT);
+        } else {
+                bp->b_src_buf = buf;
+        }
+
+        return src_page;
+}
+
+static void ocfs2_put_write_source(struct ocfs2_buffered_write_priv *bp,
+                                   struct page *page)
+{
+        if (page) {
+                kunmap(page);
+                page_cache_release(page);
+        }
+}
+
+static ssize_t ocfs2_file_buffered_write(struct file *file, loff_t *ppos,
+                                         const struct iovec *iov,
+                                         unsigned long nr_segs,
+                                         size_t count,
+                                         ssize_t o_direct_written)
+{
+        int ret = 0;
+        ssize_t copied, total = 0;
+        size_t iov_offset = 0;
+        const struct iovec *cur_iov = iov;
+        struct ocfs2_buffered_write_priv bp;
+        struct page *page;
+
+        /*
+         * handle partial DIO write.  Adjust cur_iov if needed.
+         */
+        ocfs2_set_next_iovec(&cur_iov, &iov_offset, o_direct_written);
+
+        do {
+                bp.b_cur_off = iov_offset;
+                bp.b_cur_iov = cur_iov;
+
+                page = ocfs2_get_write_source(&bp, cur_iov, iov_offset);
+                if (IS_ERR(page)) {
+                        ret = PTR_ERR(page);
+                        goto out;
+                }
+
+                copied = ocfs2_buffered_write_cluster(file, *ppos, count,
+                                                      ocfs2_map_and_write_user_data,
+                                                      &bp);
+
+                ocfs2_put_write_source(&bp, page);
+
+                if (copied < 0) {
+                        mlog_errno(copied);
+                        ret = copied;
+                        goto out;
+                }
+
+                total += copied;
+                *ppos = *ppos + copied;
+                count -= copied;
+
+                ocfs2_set_next_iovec(&cur_iov, &iov_offset, copied);
+        } while(count);
+
+out:
+        return total ? total : ret;
+}
+
+static int ocfs2_check_iovec(const struct iovec *iov, size_t *counted,
+                             unsigned long *nr_segs)
+{
+        size_t ocount;          /* original count */
+        unsigned long seg;
+
+        ocount = 0;
+        for (seg = 0; seg < *nr_segs; seg++) {
+                const struct iovec *iv = &iov[seg];
+
+                /*
+                 * If any segment has a negative length, or the cumulative
+                 * length ever wraps negative then return -EINVAL.
+                 */
+                ocount += iv->iov_len;
+                if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
+                        return -EINVAL;
+                if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
+                        continue;
+                if (seg == 0)
+                        return -EFAULT;
+                *nr_segs = seg;
+                ocount -= iv->iov_len;  /* This segment is no good */
+                break;
+        }
+
+        *counted = ocount;
+        return 0;
+}
+
 static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
                                     const struct iovec *iov,
                                     unsigned long nr_segs,
                                     loff_t pos)
 {
-        int ret, rw_level, have_alloc_sem = 0;
-        struct file *filp = iocb->ki_filp;
-        struct inode *inode = filp->f_path.dentry->d_inode;
-        int appending = filp->f_flags & O_APPEND ? 1 : 0;
-
-        mlog_entry("(0x%p, %u, '%.*s')\n", filp,
+        int ret, direct_io, appending, rw_level, have_alloc_sem  = 0;
+        int can_do_direct, sync = 0;
+        ssize_t written = 0;
+        size_t ocount;          /* original count */
+        size_t count;           /* after file limit checks */
+        loff_t *ppos = &iocb->ki_pos;
+        struct file *file = iocb->ki_filp;
+        struct inode *inode = file->f_path.dentry->d_inode;
+
+        mlog_entry("(0x%p, %u, '%.*s')\n", file,
                    (unsigned int)nr_segs,
-                   filp->f_path.dentry->d_name.len,
-                   filp->f_path.dentry->d_name.name);
+                   file->f_path.dentry->d_name.len,
+                   file->f_path.dentry->d_name.name);
 
-        /* happy write of zero bytes */
         if (iocb->ki_left == 0)
                 return 0;
 
+        ret = ocfs2_check_iovec(iov, &ocount, &nr_segs);
+        if (ret)
+                return ret;
+
+        count = ocount;
+
+        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+
+        appending = file->f_flags & O_APPEND ? 1 : 0;
+        direct_io = file->f_flags & O_DIRECT ? 1 : 0;
+
         mutex_lock(&inode->i_mutex);
+
+relock:
         /* to match setattr's i_mutex -> i_alloc_sem -> rw_lock ordering */
-        if (filp->f_flags & O_DIRECT) {
-                have_alloc_sem = 1;
+        if (direct_io) {
                 down_read(&inode->i_alloc_sem);
+                have_alloc_sem = 1;
         }
 
         /* concurrent O_DIRECT writes are allowed */
-        rw_level = (filp->f_flags & O_DIRECT) ? 0 : 1;
+        rw_level = !direct_io;
         ret = ocfs2_rw_lock(inode, rw_level);
         if (ret < 0) {
-                rw_level = -1;
                 mlog_errno(ret);
-                goto out;
+                goto out_sems;
         }
 
-        ret = ocfs2_prepare_inode_for_write(filp->f_path.dentry, &iocb->ki_pos,
-                                            iocb->ki_left, appending);
+        can_do_direct = direct_io;
+        ret = ocfs2_prepare_inode_for_write(file->f_path.dentry, ppos,
+                                            iocb->ki_left, appending,
+                                            &can_do_direct);
         if (ret < 0) {
                 mlog_errno(ret);
                 goto out;
         }
 
+        /*
+         * We can't complete the direct I/O as requested, fall back to
+         * buffered I/O.
+         */
+        if (direct_io && !can_do_direct) {
+                ocfs2_rw_unlock(inode, rw_level);
+                up_read(&inode->i_alloc_sem);
+
+                have_alloc_sem = 0;
+                rw_level = -1;
+
+                direct_io = 0;
+                sync = 1;
+                goto relock;
+        }
+
+        if (!sync && ((file->f_flags & O_SYNC) || IS_SYNC(inode)))
+                sync = 1;
+
+        /*
+         * XXX: Is it ok to execute these checks a second time?
+         */
+        ret = generic_write_checks(file, ppos, &count, S_ISBLK(inode->i_mode));
+        if (ret)
+                goto out;
+
+        /*
+         * Set pos so that sync_page_range_nolock() below understands
+         * where to start from. We might've moved it around via the
+         * calls above. The range we want to actually sync starts from
+         * *ppos here.
+         *
+         */
+        pos = *ppos;
+
         /* communicate with ocfs2_dio_end_io */
         ocfs2_iocb_set_rw_locked(iocb);
 
-        ret = generic_file_aio_write_nolock(iocb, iov, nr_segs, iocb->ki_pos);
+        if (direct_io) {
+                written = generic_file_direct_write(iocb, iov, &nr_segs, *ppos,
+                                                    ppos, count, ocount);
+                if (written < 0) {
+                        ret = written;
+                        goto out_dio;
+                }
+        } else {
+                written = ocfs2_file_buffered_write(file, ppos, iov, nr_segs,
+                                                    count, written);
+                if (written < 0) {
+                        ret = written;
+                        if (ret != -EFAULT || ret != -ENOSPC)
+                                mlog_errno(ret);
+                        goto out;
+                }
+        }
 
+out_dio:
         /* buffered aio wouldn't have proper lock coverage today */
-        BUG_ON(ret == -EIOCBQUEUED && !(filp->f_flags & O_DIRECT));
+        BUG_ON(ret == -EIOCBQUEUED && !(file->f_flags & O_DIRECT));
 
         /* 
          * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
@@ -1268,14 +1552,25 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
         }
 
 out:
+        if (rw_level != -1)
+                ocfs2_rw_unlock(inode, rw_level);
+
+out_sems:
         if (have_alloc_sem)
                 up_read(&inode->i_alloc_sem);
-        if (rw_level != -1) 
-                ocfs2_rw_unlock(inode, rw_level);
+
+        if (written > 0 && sync) {
+                ssize_t err;
+
+                err = sync_page_range_nolock(inode, file->f_mapping, pos, count);
+                if (err < 0)
+                        written = err;
+        }
+
         mutex_unlock(&inode->i_mutex);
 
         mlog_exit(ret);
-        return ret;
+        return written ? written : ret;
 }
 
 static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
@@ -1300,7 +1595,8 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
                 goto out;
         }
 
-        ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0);
+        ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0,
+                                            NULL);
         if (ret < 0) {
                 mlog_errno(ret);
                 goto out_unlock;
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index e2f6551604d0..2c4460fced52 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -46,6 +46,10 @@ int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
                                struct ocfs2_alloc_context *data_ac,
                                struct ocfs2_alloc_context *meta_ac,
                                enum ocfs2_alloc_restarted *reason);
+int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
+                          u32 clusters_to_add,
+                          struct ocfs2_alloc_context **data_ac,
+                          struct ocfs2_alloc_context **meta_ac);
 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
 int ocfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
                   struct kstat *stat);
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index faeb53f2eecf..2699f7cac21a 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -463,6 +463,38 @@ static inline unsigned long ocfs2_align_bytes_to_sectors(u64 bytes)
         return (unsigned long)((bytes + 511) >> 9);
 }
 
+static inline unsigned int ocfs2_page_index_to_clusters(struct super_block *sb,
+                                                        unsigned long pg_index)
+{
+        u32 clusters = pg_index;
+        unsigned int cbits = OCFS2_SB(sb)->s_clustersize_bits;
+
+        if (unlikely(PAGE_CACHE_SHIFT > cbits))
+                clusters = pg_index << (PAGE_CACHE_SHIFT - cbits);
+        else if (PAGE_CACHE_SHIFT < cbits)
+                clusters = pg_index >> (cbits - PAGE_CACHE_SHIFT);
+
+        return clusters;
+}
+
+/*
+ * Find the 1st page index which covers the given clusters.
+ */
+static inline unsigned long ocfs2_align_clusters_to_page_index(struct super_block *sb,
+                                                        u32 clusters)
+{
+        unsigned int cbits = OCFS2_SB(sb)->s_clustersize_bits;
+        unsigned long index = clusters;
+
+        if (PAGE_CACHE_SHIFT > cbits) {
+                index = clusters >> (PAGE_CACHE_SHIFT - cbits);
+        } else if (PAGE_CACHE_SHIFT < cbits) {
+                index = clusters << (cbits - PAGE_CACHE_SHIFT);
+        }
+
+        return index;
+}
+
 #define ocfs2_set_bit ext2_set_bit
 #define ocfs2_clear_bit ext2_clear_bit
 #define ocfs2_test_bit ext2_test_bit