1 files changed, 140 insertions, 10 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7875a75315d0..3a89cd77f307 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -475,6 +475,73 @@ out_unlock:
         return error;
 }
 
+static int should_defrag_range(struct inode *inode, u64 start, u64 len,
+                               u64 *last_len, u64 *skip, u64 *defrag_end)
+{
+        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+        struct extent_map *em = NULL;
+        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+        int ret = 1;
+
+        /*
+         * make sure that once we start defragging and extent, we keep on
+         * defragging it
+         */
+        if (start < *defrag_end)
+                return 1;
+
+        *skip = 0;
+
+        /*
+         * hopefully we have this extent in the tree already, try without
+         * the full extent lock
+         */
+        read_lock(&em_tree->lock);
+        em = lookup_extent_mapping(em_tree, start, len);
+        read_unlock(&em_tree->lock);
+
+        if (!em) {
+                /* get the big lock and read metadata off disk */
+                lock_extent(io_tree, start, start + len - 1, GFP_NOFS);
+                em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
+                unlock_extent(io_tree, start, start + len - 1, GFP_NOFS);
+
+                if (!em)
+                        return 0;
+        }
+
+        /* this will cover holes, and inline extents */
+        if (em->block_start >= EXTENT_MAP_LAST_BYTE)
+                ret = 0;
+
+        /*
+         * we hit a real extent, if it is big don't bother defragging it again
+         */
+        if ((*last_len == 0 || *last_len >= 256 * 1024) &&
+            em->len >= 256 * 1024)
+                ret = 0;
+
+        /*
+         * last_len ends up being a counter of how many bytes we've defragged.
+         * every time we choose not to defrag an extent, we reset *last_len
+         * so that the next tiny extent will force a defrag.
+         *
+         * The end result of this is that tiny extents before a single big
+         * extent will force at least part of that big extent to be defragged.
+         */
+        if (ret) {
+                *last_len += len;
+                *defrag_end = extent_map_end(em);
+        } else {
+                *last_len = 0;
+                *skip = extent_map_end(em);
+                *defrag_end = 0;
+        }
+
+        free_extent_map(em);
+        return ret;
+}
+
 static int btrfs_defrag_file(struct file *file)
 {
         struct inode *inode = fdentry(file)->d_inode;
@@ -487,37 +554,86 @@ static int btrfs_defrag_file(struct file *file)
         unsigned long total_read = 0;
         u64 page_start;
         u64 page_end;
+        u64 last_len = 0;
+        u64 skip = 0;
+        u64 defrag_end = 0;
         unsigned long i;
         int ret;
 
-        ret = btrfs_check_data_free_space(root, inode, inode->i_size);
-        if (ret)
-                return -ENOSPC;
+        if (inode->i_size == 0)
+                return 0;
+
+        last_index = (inode->i_size - 1) >> PAGE_CACHE_SHIFT;
+        i = 0;
+        while (i <= last_index) {
+                if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
+                                        PAGE_CACHE_SIZE, &last_len, &skip,
+                                        &defrag_end)) {
+                        unsigned long next;
+                        /*
+                         * the should_defrag function tells us how much to skip
+                         * bump our counter by the suggested amount
+                         */
+                        next = (skip + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+                        i = max(i + 1, next);
+                        continue;
+                }
 
-        mutex_lock(&inode->i_mutex);
-        last_index = inode->i_size >> PAGE_CACHE_SHIFT;
-        for (i = 0; i <= last_index; i++) {
                 if (total_read % ra_pages == 0) {
                         btrfs_force_ra(inode->i_mapping, &file->f_ra, file, i,
                                        min(last_index, i + ra_pages - 1));
                 }
                 total_read++;
+                mutex_lock(&inode->i_mutex);
+
+                ret = btrfs_check_data_free_space(root, inode, PAGE_CACHE_SIZE);
+                if (ret) {
+                        ret = -ENOSPC;
+                        break;
+                }
+
+                ret = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
+                if (ret) {
+                        btrfs_free_reserved_data_space(root, inode,
+                                                       PAGE_CACHE_SIZE);
+                        ret = -ENOSPC;
+                        break;
+                }
 again:
+                if (inode->i_size == 0 ||
+                    i > ((inode->i_size - 1) >> PAGE_CACHE_SHIFT)) {
+                        ret = 0;
+                        goto err_reservations;
+                }
+
                 page = grab_cache_page(inode->i_mapping, i);
                 if (!page)
-                        goto out_unlock;
+                        goto err_reservations;
+
                 if (!PageUptodate(page)) {
                         btrfs_readpage(NULL, page);
                         lock_page(page);
                         if (!PageUptodate(page)) {
                                 unlock_page(page);
                                 page_cache_release(page);
-                                goto out_unlock;
+                                goto err_reservations;
                         }
                 }
 
+                if (page->mapping != inode->i_mapping) {
+                        unlock_page(page);
+                        page_cache_release(page);
+                        goto again;
+                }
+
                 wait_on_page_writeback(page);
 
+                if (PageDirty(page)) {
+                        btrfs_free_reserved_data_space(root, inode,
+                                                       PAGE_CACHE_SIZE);
+                        goto loop_unlock;
+                }
+
                 page_start = (u64)page->index << PAGE_CACHE_SHIFT;
                 page_end = page_start + PAGE_CACHE_SIZE - 1;
                 lock_extent(io_tree, page_start, page_end, GFP_NOFS);
@@ -538,18 +654,32 @@ again:
                  * page if it is dirtied again later
                  */
                 clear_page_dirty_for_io(page);
+                clear_extent_bits(&BTRFS_I(inode)->io_tree, page_start,
+                                  page_end, EXTENT_DIRTY | EXTENT_DELALLOC |
+                                  EXTENT_DO_ACCOUNTING, GFP_NOFS);
 
                 btrfs_set_extent_delalloc(inode, page_start, page_end);
+                ClearPageChecked(page);
                 set_page_dirty(page);
                 unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
+
+loop_unlock:
                 unlock_page(page);
                 page_cache_release(page);
+                mutex_unlock(&inode->i_mutex);
+
+                btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
                 balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
+                i++;
         }
 
-out_unlock:
-        mutex_unlock(&inode->i_mutex);
         return 0;
+
+err_reservations:
+        mutex_unlock(&inode->i_mutex);
+        btrfs_free_reserved_data_space(root, inode, PAGE_CACHE_SIZE);
+        btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
+        return ret;
 }
 
 static noinline int btrfs_ioctl_resize(struct btrfs_root *root,