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Commit 81def6b9 authored by Joern Engel's avatar Joern Engel
Browse files

Simplify and fix pad_wbuf 



A comment in the old code read:
        /* The math in this function can surely use some love */

And indeed it did.  In the case that area->a_used_bytes is exactly
4096 bytes below segment size it fell apart.  pad_wbuf is now split
into two helpers that are significantly less complicated.

Signed-off-by: default avatarJoern Engel <joern@logfs.org>
parent 19321917

fs/logfs/segment.c

+30 −22
Original line number Diff line number Diff line
@@ -93,47 +93,55 @@ void __logfs_buf_write(struct logfs_area *area, u64 ofs, void *buf, size_t len, 
	} while (len);

}



/*

 * bdev_writeseg will write full pages.  Memset the tail to prevent data leaks.

 */

static void pad_wbuf(struct logfs_area *area, int final)

static void pad_partial_page(struct logfs_area *area)

{

	struct super_block *sb = area->a_sb;

	struct logfs_super *super = logfs_super(sb);

	struct page *page;

	u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes);

	pgoff_t index = ofs >> PAGE_SHIFT;

	long offset = ofs & (PAGE_SIZE-1);

	u32 len = PAGE_SIZE - offset;



	if (len == PAGE_SIZE) {

		/* The math in this function can surely use some love */

		len = 0;

	}

	if (len) {

		BUG_ON(area->a_used_bytes >= super->s_segsize);



		page = get_mapping_page(area->a_sb, index, 0);

	if (len % PAGE_SIZE) {

		page = get_mapping_page(sb, index, 0);

		BUG_ON(!page); /* FIXME: reserve a pool */

		memset(page_address(page) + offset, 0xff, len);

		SetPagePrivate(page);

		page_cache_release(page);

	}

}



	if (!final)

		return;

static void pad_full_pages(struct logfs_area *area)

{

	struct super_block *sb = area->a_sb;

	struct logfs_super *super = logfs_super(sb);

	u64 ofs = dev_ofs(sb, area->a_segno, area->a_used_bytes);

	u32 len = super->s_segsize - area->a_used_bytes;

	pgoff_t index = PAGE_CACHE_ALIGN(ofs) >> PAGE_CACHE_SHIFT;

	pgoff_t no_indizes = len >> PAGE_CACHE_SHIFT;

	struct page *page;



	area->a_used_bytes += len;

	for ( ; area->a_used_bytes < super->s_segsize;

			area->a_used_bytes += PAGE_SIZE) {

		/* Memset another page */

		index++;

		page = get_mapping_page(area->a_sb, index, 0);

	while (no_indizes) {

		page = get_mapping_page(sb, index, 0);

		BUG_ON(!page); /* FIXME: reserve a pool */

		memset(page_address(page), 0xff, PAGE_SIZE);

		SetPageUptodate(page);

		memset(page_address(page), 0xff, PAGE_CACHE_SIZE);

		SetPagePrivate(page);

		page_cache_release(page);

		index++;

		no_indizes--;

	}

}



/*

 * bdev_writeseg will write full pages.  Memset the tail to prevent data leaks.

 * Also make sure we allocate (and memset) all pages for final writeout.

 */

static void pad_wbuf(struct logfs_area *area, int final)

{

	pad_partial_page(area);

	if (final)

		pad_full_pages(area);

}



/*