In subpage-blocksize scenario, extent allocations for only some of the
dirty blocks of a page can succeed, while allocation for rest of the
blocks can fail. This patch allows I/O against such pages to be
submitted.

Signed-off-by: Chandan Rajendra <chan...@linux.vnet.ibm.com>
---
 fs/btrfs/extent_io.c | 27 ++++++++++++++-------------
 fs/btrfs/inode.c     | 39 ++++++++++++++++++++++++++-------------
 2 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0465311..74e27f9 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1863,17 +1863,23 @@ void extent_clear_unlock_delalloc(struct inode *inode, 
u64 start, u64 end,
                        if (page_ops & PAGE_SET_PRIVATE2)
                                SetPagePrivate2(pages[i]);
 
+                       if (page_ops & PAGE_SET_ERROR)
+                               SetPageError(pages[i]);
+
                        if (pages[i] == locked_page) {
                                put_page(pages[i]);
                                continue;
                        }
-                       if (page_ops & PAGE_CLEAR_DIRTY)
+
+                       if ((page_ops & PAGE_CLEAR_DIRTY)
+                               && !PagePrivate2(pages[i]))
                                clear_page_dirty_for_io(pages[i]);
-                       if (page_ops & PAGE_SET_WRITEBACK)
+                       if ((page_ops & PAGE_SET_WRITEBACK)
+                               && !PagePrivate2(pages[i]))
                                set_page_writeback(pages[i]);
-                       if (page_ops & PAGE_SET_ERROR)
-                               SetPageError(pages[i]);
-                       if (page_ops & PAGE_END_WRITEBACK)
+
+                       if ((page_ops & PAGE_END_WRITEBACK)
+                               && !PagePrivate2(pages[i]))
                                end_page_writeback(pages[i]);
                        if (page_ops & PAGE_UNLOCK)
                                unlock_page(pages[i]);
@@ -2565,7 +2571,7 @@ void end_extent_writepage(struct page *page, int err, u64 
start, u64 end)
                        uptodate = 0;
        }
 
-       if (!uptodate) {
+       if (!uptodate || PageError(page)) {
                ClearPageUptodate(page);
                SetPageError(page);
                ret = ret < 0 ? ret : -EIO;
@@ -3420,7 +3426,6 @@ static noinline_for_stack int writepage_delalloc(struct 
inode *inode,
                                               nr_written);
                /* File system has been set read-only */
                if (ret) {
-                       SetPageError(page);
                        /* fill_delalloc should be return < 0 for error
                         * but just in case, we use > 0 here meaning the
                         * IO is started, so we don't want to return > 0
@@ -3641,7 +3646,6 @@ static int __extent_writepage(struct page *page, struct 
writeback_control *wbc,
        struct inode *inode = page->mapping->host;
        struct extent_page_data *epd = data;
        u64 start = page_offset(page);
-       u64 page_end = start + PAGE_SIZE - 1;
        int ret;
        int nr = 0;
        size_t pg_offset = 0;
@@ -3686,7 +3690,7 @@ static int __extent_writepage(struct page *page, struct 
writeback_control *wbc,
        ret = writepage_delalloc(inode, page, wbc, epd, start, &nr_written);
        if (ret == 1)
                goto done_unlocked;
-       if (ret)
+       if (ret && !PagePrivate2(page))
                goto done;
 
        ret = __extent_writepage_io(inode, page, wbc, epd,
@@ -3700,10 +3704,7 @@ done:
                set_page_writeback(page);
                end_page_writeback(page);
        }
-       if (PageError(page)) {
-               ret = ret < 0 ? ret : -EIO;
-               end_extent_writepage(page, ret, start, page_end);
-       }
+
        unlock_page(page);
        return ret;
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e85865b..a6bb415 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -943,6 +943,8 @@ static noinline int cow_file_range(struct inode *inode,
        struct btrfs_key ins;
        struct extent_map *em;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+       struct btrfs_ordered_extent *ordered;
+       unsigned long page_ops, extent_ops;
        int ret = 0;
 
        if (btrfs_is_free_space_inode(inode)) {
@@ -987,8 +989,6 @@ static noinline int cow_file_range(struct inode *inode,
        btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);
 
        while (disk_num_bytes > 0) {
-               unsigned long op;
-
                cur_alloc_size = disk_num_bytes;
                ret = btrfs_reserve_extent(root, cur_alloc_size,
                                           root->sectorsize, 0, alloc_hint,
@@ -1041,7 +1041,7 @@ static noinline int cow_file_range(struct inode *inode,
                        ret = btrfs_reloc_clone_csums(inode, start,
                                                      cur_alloc_size);
                        if (ret)
-                               goto out_drop_extent_cache;
+                               goto out_remove_ordered_extent;
                }
 
                btrfs_dec_block_group_reservations(root->fs_info, ins.objectid);
@@ -1056,13 +1056,12 @@ static noinline int cow_file_range(struct inode *inode,
                 * Do set the Private2 bit so we know this page was properly
                 * setup for writepage
                 */
-               op = unlock ? PAGE_UNLOCK : 0;
-               op |= PAGE_SET_PRIVATE2;
-
+               page_ops = unlock ? PAGE_UNLOCK : 0;
+               page_ops |= PAGE_SET_PRIVATE2;
+               extent_ops = EXTENT_LOCKED | EXTENT_DELALLOC;
                extent_clear_unlock_delalloc(inode, start,
-                                            start + ram_size - 1, locked_page,
-                                            EXTENT_LOCKED | EXTENT_DELALLOC,
-                                            op);
+                                       start + ram_size - 1, locked_page,
+                                       extent_ops, page_ops);
                disk_num_bytes -= cur_alloc_size;
                num_bytes -= cur_alloc_size;
                alloc_hint = ins.objectid + ins.offset;
@@ -1071,17 +1070,31 @@ static noinline int cow_file_range(struct inode *inode,
 out:
        return ret;
 
+out_remove_ordered_extent:
+       ordered = btrfs_lookup_ordered_extent(inode, start);
+       BUG_ON(!ordered);
+       btrfs_remove_ordered_extent(inode, ordered);
+       /* once for us */
+       btrfs_put_ordered_extent(ordered);
+       /* once for the tree */
+       btrfs_put_ordered_extent(ordered);
+
 out_drop_extent_cache:
        btrfs_drop_extent_cache(inode, start, start + ram_size - 1, 0);
+
 out_reserve:
        btrfs_dec_block_group_reservations(root->fs_info, ins.objectid);
        btrfs_free_reserved_extent(root, ins.objectid, ins.offset, 1);
+
 out_unlock:
+       page_ops = unlock ? PAGE_UNLOCK : 0;
+       page_ops |= PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK
+               | PAGE_SET_ERROR;
+       extent_ops = EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING
+               | EXTENT_DEFRAG;
+
        extent_clear_unlock_delalloc(inode, start, end, locked_page,
-                                    EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
-                                    EXTENT_DELALLOC | EXTENT_DEFRAG,
-                                    PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
-                                    PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK);
+                               extent_ops, page_ops);
        goto out;
 }
 
-- 
2.1.0

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