[PATCH 1/2] iomap: Support large pages

[Matthew Wilcox <willy@infradead.org>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Change iomap_page from a statically sized uptodate bitmap to a
dynamically allocated uptodate bitmap, allowing an arbitrarily large page.

Calculate the size of the page everywhere instead of using a base
PAGE_SIZE.

Based on a patch from Christoph Hellwig.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/iomap/buffered-io.c | 82 ++++++++++++++++++++++++++----------------
 include/linux/iomap.h  |  2 +-
 2 files changed, 53 insertions(+), 31 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index e25901ae3ff4..4d56b8060b6c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -23,14 +23,17 @@ static struct iomap_page *
 iomap_page_create(struct inode *inode, struct page *page)
 {
 	struct iomap_page *iop = to_iomap_page(page);
+	unsigned int nbits;
 
-	if (iop || i_blocksize(inode) == PAGE_SIZE)
+	if (iop || i_blocksize(inode) == page_size(page))
 		return iop;
 
-	iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
+	nbits = BITS_TO_LONGS(page_size(page) / SECTOR_SIZE);
+	iop = kmalloc(struct_size(iop, uptodate, nbits),
+			GFP_NOFS | __GFP_NOFAIL);
 	atomic_set(&iop->read_count, 0);
 	atomic_set(&iop->write_count, 0);
-	bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
+	bitmap_zero(iop->uptodate, nbits);
 
 	/*
 	 * migrate_page_move_mapping() assumes that pages with private data have
@@ -61,15 +64,16 @@ iomap_page_release(struct page *page)
  * Calculate the range inside the page that we actually need to read.
  */
 static void
-iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
+iomap_adjust_read_range(struct inode *inode, struct page *page,
 		loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
 {
+	struct iomap_page *iop = to_iomap_page(page);
 	loff_t orig_pos = *pos;
 	loff_t isize = i_size_read(inode);
 	unsigned block_bits = inode->i_blkbits;
 	unsigned block_size = (1 << block_bits);
-	unsigned poff = offset_in_page(*pos);
-	unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
+	unsigned poff = *pos & (page_size(page) - 1);
+	unsigned plen = min_t(loff_t, page_size(page) - poff, length);
 	unsigned first = poff >> block_bits;
 	unsigned last = (poff + plen - 1) >> block_bits;
 
@@ -107,7 +111,8 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
 	 * page cache for blocks that are entirely outside of i_size.
 	 */
 	if (orig_pos <= isize && orig_pos + length > isize) {
-		unsigned end = offset_in_page(isize - 1) >> block_bits;
+		unsigned end = (isize - 1) & (page_size(page) - 1) >>
+				block_bits;
 
 		if (first <= end && last > end)
 			plen -= (last - end) * block_size;
@@ -128,7 +133,7 @@ iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
 	bool uptodate = true;
 
 	if (iop) {
-		for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
+		for (i = 0; i < page_size(page) / i_blocksize(inode); i++) {
 			if (i >= first && i <= last)
 				set_bit(i, iop->uptodate);
 			else if (!test_bit(i, iop->uptodate))
@@ -194,11 +199,12 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
 		return;
 
 	BUG_ON(page->index);
-	BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
+	BUG_ON(size > page_size(page) - ((unsigned long)iomap->inline_data &
+						(page_size(page) - 1)));
 
 	addr = kmap_atomic(page);
 	memcpy(addr, iomap->inline_data, size);
-	memset(addr + size, 0, PAGE_SIZE - size);
+	memset(addr + size, 0, page_size(page) - size);
 	kunmap_atomic(addr);
 	SetPageUptodate(page);
 }
@@ -218,11 +224,11 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 	if (iomap->type == IOMAP_INLINE) {
 		WARN_ON_ONCE(pos);
 		iomap_read_inline_data(inode, page, iomap);
-		return PAGE_SIZE;
+		return page_size(page);
 	}
 
 	/* zero post-eof blocks as the page may be mapped */
-	iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
+	iomap_adjust_read_range(inode, page, &pos, length, &poff, &plen);
 	if (plen == 0)
 		goto done;
 
@@ -258,7 +264,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 
 	if (!ctx->bio || !is_contig || bio_full(ctx->bio, plen)) {
 		gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
-		int nr_vecs = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		int nr_vecs = (length + page_size(page) - 1) >> page_shift(page);
 
 		if (ctx->bio)
 			submit_bio(ctx->bio);
@@ -293,9 +299,9 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops)
 	unsigned poff;
 	loff_t ret;
 
-	for (poff = 0; poff < PAGE_SIZE; poff += ret) {
+	for (poff = 0; poff < page_size(page); poff += ret) {
 		ret = iomap_apply(inode, page_offset(page) + poff,
-				PAGE_SIZE - poff, 0, ops, &ctx,
+				page_size(page) - poff, 0, ops, &ctx,
 				iomap_readpage_actor);
 		if (ret <= 0) {
 			WARN_ON_ONCE(ret == 0);
@@ -342,7 +348,7 @@ iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos,
 		 * readpages call itself as every page gets checked again once
 		 * actually needed.
 		 */
-		*done += PAGE_SIZE;
+		*done += page_size(page);
 		put_page(page);
 	}
 
@@ -355,9 +361,14 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
 {
 	struct iomap_readpage_ctx *ctx = data;
 	loff_t done, ret;
+	size_t pg_left = 0;
+
+	if (ctx->cur_page)
+		pg_left = page_size(ctx->cur_page) -
+					(pos & (page_size(ctx->cur_page) - 1));
 
 	for (done = 0; done < length; done += ret) {
-		if (ctx->cur_page && offset_in_page(pos + done) == 0) {
+		if (ctx->cur_page && pg_left == 0) {
 			if (!ctx->cur_page_in_bio)
 				unlock_page(ctx->cur_page);
 			put_page(ctx->cur_page);
@@ -369,9 +380,11 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
 			if (!ctx->cur_page)
 				break;
 			ctx->cur_page_in_bio = false;
+			pg_left = page_size(ctx->cur_page);
 		}
 		ret = iomap_readpage_actor(inode, pos + done, length - done,
 				ctx, iomap);
+		pg_left -= ret;
 	}
 
 	return done;
@@ -386,8 +399,9 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages,
 		.is_readahead	= true,
 	};
 	loff_t pos = page_offset(list_entry(pages->prev, struct page, lru));
-	loff_t last = page_offset(list_entry(pages->next, struct page, lru));
-	loff_t length = last - pos + PAGE_SIZE, ret = 0;
+	struct page *last_page = list_entry(pages->next, struct page, lru);
+	loff_t length = page_offset(last_page) - pos + page_size(last_page);
+	loff_t ret = 0;
 
 	while (length > 0) {
 		ret = iomap_apply(mapping->host, pos, length, 0, ops,
@@ -435,7 +449,7 @@ iomap_is_partially_uptodate(struct page *page, unsigned long from,
 	unsigned i;
 
 	/* Limit range to one page */
-	len = min_t(unsigned, PAGE_SIZE - from, count);
+	len = min_t(unsigned, page_size(page) - from, count);
 
 	/* First and last blocks in range within page */
 	first = from >> inode->i_blkbits;
@@ -474,7 +488,7 @@ iomap_invalidatepage(struct page *page, unsigned int offset, unsigned int len)
 	 * If we are invalidating the entire page, clear the dirty state from it
 	 * and release it to avoid unnecessary buildup of the LRU.
 	 */
-	if (offset == 0 && len == PAGE_SIZE) {
+	if (offset == 0 && len == page_size(page)) {
 		WARN_ON_ONCE(PageWriteback(page));
 		cancel_dirty_page(page);
 		iomap_page_release(page);
@@ -550,18 +564,20 @@ static int
 __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
 		struct page *page, struct iomap *iomap)
 {
-	struct iomap_page *iop = iomap_page_create(inode, page);
 	loff_t block_size = i_blocksize(inode);
 	loff_t block_start = pos & ~(block_size - 1);
 	loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1);
-	unsigned from = offset_in_page(pos), to = from + len, poff, plen;
+	unsigned from = pos & (page_size(page) - 1);
+	unsigned to = from + len;
+	unsigned poff, plen;
 	int status = 0;
 
 	if (PageUptodate(page))
 		return 0;
+	iomap_page_create(inode, page);
 
 	do {
-		iomap_adjust_read_range(inode, iop, &block_start,
+		iomap_adjust_read_range(inode, page, &block_start,
 				block_end - block_start, &poff, &plen);
 		if (plen == 0)
 			break;
@@ -673,7 +689,7 @@ __iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
 	 */
 	if (unlikely(copied < len && !PageUptodate(page)))
 		return 0;
-	iomap_set_range_uptodate(page, offset_in_page(pos), len);
+	iomap_set_range_uptodate(page, pos & (page_size(page) - 1), len);
 	iomap_set_page_dirty(page);
 	return copied;
 }
@@ -685,7 +701,9 @@ iomap_write_end_inline(struct inode *inode, struct page *page,
 	void *addr;
 
 	WARN_ON_ONCE(!PageUptodate(page));
-	BUG_ON(pos + copied > PAGE_SIZE - offset_in_page(iomap->inline_data));
+	BUG_ON(pos + copied > page_size(page) -
+			((unsigned long)iomap->inline_data &
+			 (page_size(page) - 1)));
 
 	addr = kmap_atomic(page);
 	memcpy(iomap->inline_data + pos, addr + pos, copied);
@@ -749,6 +767,10 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		unsigned long bytes;	/* Bytes to write to page */
 		size_t copied;		/* Bytes copied from user */
 
+		/*
+		 * XXX: We don't know what size page we'll find in the
+		 * page cache, so only copy up to a regular page boundary.
+		 */
 		offset = offset_in_page(pos);
 		bytes = min_t(unsigned long, PAGE_SIZE - offset,
 						iov_iter_count(i));
@@ -1047,11 +1069,11 @@ vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
 		goto out_unlock;
 	}
 
-	/* page is wholly or partially inside EOF */
-	if (((page->index + 1) << PAGE_SHIFT) > size)
-		length = offset_in_page(size);
+	/* page is wholly or partially beyond EOF */
+	if (((page->index + compound_nr(page)) << PAGE_SHIFT) > size)
+		length = size & (page_size(page) - 1);
 	else
-		length = PAGE_SIZE;
+		length = page_size(page);
 
 	offset = page_offset(page);
 	while (length > 0) {
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index bc499ceae392..86be24a8259b 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -139,7 +139,7 @@ loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
 struct iomap_page {
 	atomic_t		read_count;
 	atomic_t		write_count;
-	DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
+	unsigned long		uptodate[];
 };
 
 static inline struct iomap_page *to_iomap_page(struct page *page)
-- 
2.20.1