logfs: commit reservations under space pressure

Ensures we only return -ENOSPC when there really is no space.

Signed-off-by: Joern Engel <joern@logfs.org>

3 files changed, 24 insertions, 4 deletions

diff --git a/fs/logfs/file.c b/fs/logfs/file.c
index 370f367a933e..bf9b1cf953a6 100644
--- a/fs/logfs/file.c
+++ b/fs/logfs/file.c
@@ -161,7 +161,17 @@ static int logfs_writepage(struct page *page, struct writeback_control *wbc)
 
 static void logfs_invalidatepage(struct page *page, unsigned long offset)
 {
-        move_page_to_btree(page);
+        struct logfs_block *block = logfs_block(page);
+
+        if (block->reserved_bytes) {
+                struct super_block *sb = page->mapping->host->i_sb;
+                struct logfs_super *super = logfs_super(sb);
+
+                super->s_dirty_pages -= block->reserved_bytes;
+                block->ops->free_block(sb, block);
+                BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
+        } else
+                move_page_to_btree(page);
         BUG_ON(PagePrivate(page) || page->private);
 }
 
diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h
index 32bf55616e56..26a9458e6b13 100644
--- a/fs/logfs/logfs.h
+++ b/fs/logfs/logfs.h
@@ -394,6 +394,7 @@ struct logfs_super {
         int      s_lock_count;
         mempool_t *s_block_pool;                /* struct logfs_block pool */
         mempool_t *s_shadow_pool;               /* struct logfs_shadow pool */
+        struct list_head s_writeback_list;      /* writeback pages */
         /*
          * Space accounting:
          * - s_used_bytes specifies space used to store valid data objects.
diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index e37cee3b1007..0718d112a1a5 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -1095,17 +1095,25 @@ static int logfs_reserve_bytes(struct inode *inode, int bytes)
 int get_page_reserve(struct inode *inode, struct page *page)
 {
         struct logfs_super *super = logfs_super(inode->i_sb);
+        struct logfs_block *block = logfs_block(page);
         int ret;
 
-        if (logfs_block(page) && logfs_block(page)->reserved_bytes)
+        if (block && block->reserved_bytes)
                 return 0;
 
         logfs_get_wblocks(inode->i_sb, page, WF_LOCK);
-        ret = logfs_reserve_bytes(inode, 6 * LOGFS_MAX_OBJECTSIZE);
+        while ((ret = logfs_reserve_bytes(inode, 6 * LOGFS_MAX_OBJECTSIZE)) &&
+                        !list_empty(&super->s_writeback_list)) {
+                block = list_entry(super->s_writeback_list.next,
+                                struct logfs_block, alias_list);
+                block->ops->write_block(block);
+        }
         if (!ret) {
                 alloc_data_block(inode, page);
-                logfs_block(page)->reserved_bytes += 6 * LOGFS_MAX_OBJECTSIZE;
+                block = logfs_block(page);
+                block->reserved_bytes += 6 * LOGFS_MAX_OBJECTSIZE;
                 super->s_dirty_pages += 6 * LOGFS_MAX_OBJECTSIZE;
+                list_move_tail(&block->alias_list, &super->s_writeback_list);
         }
         logfs_put_wblocks(inode->i_sb, page, WF_LOCK);
         return ret;
@@ -2251,6 +2259,7 @@ int logfs_init_rw(struct super_block *sb)
         int min_fill = 3 * super->s_no_blocks;
 
         INIT_LIST_HEAD(&super->s_object_alias);
+        INIT_LIST_HEAD(&super->s_writeback_list);
         mutex_init(&super->s_write_mutex);
         super->s_block_pool = mempool_create_kmalloc_pool(min_fill,
                         sizeof(struct logfs_block));