logfs: update page reference count for pined pages

LogFS sets PG_private flag to indicate a pined page. We assumed that
marking a page as private is enough to ensure its existence. But
instead it is necessary to hold a reference count to the page.

The change resolves the following BUG

BUG: Bad page state in process flush-253:16  pfn:6a6d0
page flags: 0x100000000000808(uptodate|private)

Suggested-and-Acked-by: Joern Engel <joern@logfs.org>
Signed-off-by: Prasad Joshi <prasadjoshi.linux@gmail.com>

diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index 2ac4217b7901cb60b726986fc964f29b3e09168f..6d663e8ea6dad22792bbc873c268fdd6d86390ac 100644 (file)
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -560,8 +560,13 @@ static void inode_free_block(struct super_block *sb, struct logfs_block *block)
 static void indirect_free_block(struct super_block *sb,
                struct logfs_block *block)
 {
-       ClearPagePrivate(block->page);
-       block->page->private = 0;
+       struct page *page = block->page;
+
+       if (PagePrivate(page)) {
+               ClearPagePrivate(page);
+               page_cache_release(page);
+               set_page_private(page, 0);
+       }
        __free_block(sb, block);
 }
 
@@ -650,8 +655,11 @@ static void alloc_data_block(struct inode *inode, struct page *page)
        logfs_unpack_index(page->index, &bix, &level);
        block = __alloc_block(inode->i_sb, inode->i_ino, bix, level);
        block->page = page;
+
        SetPagePrivate(page);
-       page->private = (unsigned long)block;
+       page_cache_get(page);
+       set_page_private(page, (unsigned long) block);
+
        block->ops = &indirect_block_ops;
 }
 
@@ -1901,8 +1909,11 @@ static void move_page_to_inode(struct inode *inode, struct page *page)
        li->li_block = block;
 
        block->page = NULL;
-       page->private = 0;
-       ClearPagePrivate(page);
+       if (PagePrivate(page)) {
+               ClearPagePrivate(page);
+               page_cache_release(page);
+               set_page_private(page, 0);
+       }
 }
 
 static void move_inode_to_page(struct page *page, struct inode *inode)
@@ -1918,8 +1929,12 @@ static void move_inode_to_page(struct page *page, struct inode *inode)
        BUG_ON(PagePrivate(page));
        block->ops = &indirect_block_ops;
        block->page = page;
-       page->private = (unsigned long)block;
-       SetPagePrivate(page);
+
+       if (!PagePrivate(page)) {
+               SetPagePrivate(page);
+               page_cache_get(page);
+               set_page_private(page, (unsigned long) block);
+       }
 
        block->inode = NULL;
        li->li_block = NULL;

diff --git a/fs/logfs/segment.c b/fs/logfs/segment.c
index 9d5187353255ddf630a44afcb5e7d020dc8dd25c..6aee6092860df3d0ffb81e9b606df20d700d9b9f 100644 (file)
--- a/fs/logfs/segment.c
+++ b/fs/logfs/segment.c
@@ -86,7 +86,11 @@ int __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len,
                BUG_ON(!page); /* FIXME: reserve a pool */
                SetPageUptodate(page);
                memcpy(page_address(page) + offset, buf, copylen);
-               SetPagePrivate(page);
+
+               if (!PagePrivate(page)) {
+                       SetPagePrivate(page);
+                       page_cache_get(page);
+               }
                page_cache_release(page);
 
                buf += copylen;
@@ -110,7 +114,10 @@ static void pad_partial_page(struct logfs_area *area)
                page = get_mapping_page(sb, index, 0);
                BUG_ON(!page); /* FIXME: reserve a pool */
                memset(page_address(page) + offset, 0xff, len);
-               SetPagePrivate(page);
+               if (!PagePrivate(page)) {
+                       SetPagePrivate(page);
+                       page_cache_get(page);
+               }
                page_cache_release(page);
        }
 }
@@ -130,7 +137,10 @@ static void pad_full_pages(struct logfs_area *area)
                BUG_ON(!page); /* FIXME: reserve a pool */
                SetPageUptodate(page);
                memset(page_address(page), 0xff, PAGE_CACHE_SIZE);
-               SetPagePrivate(page);
+               if (!PagePrivate(page)) {
+                       SetPagePrivate(page);
+                       page_cache_get(page);
+               }
                page_cache_release(page);
                index++;
                no_indizes--;
@@ -485,8 +495,12 @@ static void move_btree_to_page(struct inode *inode, struct page *page,
                mempool_free(item, super->s_alias_pool);
        }
        block->page = page;
-       SetPagePrivate(page);
-       page->private = (unsigned long)block;
+
+       if (!PagePrivate(page)) {
+               SetPagePrivate(page);
+               page_cache_get(page);
+               set_page_private(page, (unsigned long) block);
+       }
        block->ops = &indirect_block_ops;
        initialize_block_counters(page, block, data, 0);
 }
@@ -536,8 +550,12 @@ void move_page_to_btree(struct page *page)
                list_add(&item->list, &block->item_list);
        }
        block->page = NULL;
-       ClearPagePrivate(page);
-       page->private = 0;
+
+       if (PagePrivate(page)) {
+               ClearPagePrivate(page);
+               page_cache_release(page);
+               set_page_private(page, 0);
+       }
        block->ops = &btree_block_ops;
        err = alias_tree_insert(block->sb, block->ino, block->bix, block->level,
                        block);
@@ -702,7 +720,10 @@ void freeseg(struct super_block *sb, u32 segno)
                page = find_get_page(mapping, ofs >> PAGE_SHIFT);
                if (!page)
                        continue;
-               ClearPagePrivate(page);
+               if (PagePrivate(page)) {
+                       ClearPagePrivate(page);
+                       page_cache_release(page);
+               }
                page_cache_release(page);
        }
 }