ext2: buffer related fixes

Data corruption fix in cases where a buffer could be both in the disk's page cache and a file's disk cache (this fix is not perfect). Zero out file holes now that filemap feeds us unzeroed pages. Signed-off-by: Pedro Falcato <[email protected]>
heatd · Nov 29, 2024 · a635188 · a635188
1 parent c655053
commit a635188
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Showing 4 changed files with 32 additions and 2 deletions.
diff --git a/kernel/include/onyx/page.h b/kernel/include/onyx/page.h
@@ -627,6 +627,12 @@ PAGEFLAG_OPS(buffer, BUFFER);
 struct vm_object *page_vmobj(struct page *page);
 unsigned long page_pgoff(struct page *page);
 
+static inline void page_zero_range(struct page *page, unsigned int off, unsigned int len)
+{
+    u8 *ptr = (u8 *) PAGE_TO_VIRT(page);
+    memset(ptr + off, 0, len);
+}
+
 __END_CDECLS
 
 #endif
diff --git a/kernel/kernel/fs/buffer.cpp b/kernel/kernel/fs/buffer.cpp
@@ -800,6 +800,25 @@ void block_buf_tear_down_assoc(struct vm_object *object)
     }
 }
 
+static void bforget(struct block_buf *buf)
+{
+    /* De-dirty the buffer (and page) if possible */
+    struct page *page = buf->this_page;
+    spin_lock(&buf->pagestate_lock);
+    bb_clear_flag(buf, BLOCKBUF_FLAG_DIRTY);
+    bool isdirty = false;
+    for (struct block_buf *b = (struct block_buf *) page->priv; b; b = b->next)
+    {
+        if (bb_test_flag(b, BLOCKBUF_FLAG_DIRTY))
+            isdirty = true;
+    }
+
+    if (!isdirty)
+        page_clear_dirty(page);
+    spin_unlock(&buf->pagestate_lock);
+    block_buf_put(buf);
+}
+
 /**
  * @brief Forget a block_buf's inode
  * This will remove it from the assoc list
@@ -823,6 +842,8 @@ void block_buf_forget_inode(struct block_buf *buf)
         buf->assoc_buffers_obj = nullptr;
         break;
     }
+
+    bforget(buf);
 }
 
 void buffer_free_page(struct vm_object *vmo, struct page *page)

diff --git a/kernel/kernel/fs/ext2/ext2.cpp b/kernel/kernel/fs/ext2/ext2.cpp
@@ -206,7 +206,7 @@ int ext2_map_page(struct page *page, size_t off, struct inode *ino)
         if (block == EXT2_ERR_INV_BLOCK)
         {
             // Zero the block, since it's a hole
-            memset((char *) PAGE_TO_VIRT(page) + curr_off, 0, sb->block_size);
+            page_zero_range(page, b->page_off, sb->block_size);
             bb_test_and_set(b, BLOCKBUF_FLAG_UPTODATE);
         }
         else
@@ -236,6 +236,9 @@ ssize_t ext2_readpage(struct page *page, size_t off, struct inode *ino)
     for (struct block_buf *b = (struct block_buf *) page->priv; b != nullptr; b = b->next)
     {
         sector_t block = b->block_nr;
+        if (bb_test_flag(b, BLOCKBUF_FLAG_UPTODATE))
+            continue;
+
         if (block != EXT2_ERR_INV_BLOCK)
         {
             /* TODO: Coalesce reads */

diff --git a/kernel/kernel/fs/ext2/inode.cpp b/kernel/kernel/fs/ext2/inode.cpp
@@ -351,7 +351,7 @@ int ext2_truncate_branch(ext2_block_no block, ext2_block_coords &curr_coords, st
         return EXT2_TRUNCATED_PARTIALLY;
     /* Truncated fully, we can free this block */
     /* Note: we must "forget" the inode block buf */
-    block_buf_forget_inode(buf);
+    block_buf_forget_inode(buf.release());
     sb->free_block(block);
     ino->i_blocks -= sb->block_size >> 9;
     return EXT2_TRUNCATED_FULLY;