3 files changed, 120 insertions, 189 deletions

diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
index c68a36688474..be0087825ae0 100644
--- a/fs/xfs/libxfs/xfs_ag.c
+++ b/fs/xfs/libxfs/xfs_ag.c
@@ -43,7 +43,6 @@ xfs_get_aghdr_buf(
 	if (error)
 		return error;
 
-	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
 	bp->b_bn = blkno;
 	bp->b_maps[0].bm_bn = blkno;
 	bp->b_ops = ops;
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 592800c8852f..a55471612150 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -22,9 +22,6 @@
 
 static kmem_zone_t *xfs_buf_zone;
 
-#define xb_to_gfp(flags) \
-	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
-
 /*
  * Locking orders
  *
@@ -79,7 +76,7 @@ static inline int
 xfs_buf_vmap_len(
 	struct xfs_buf	*bp)
 {
-	return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
+	return (bp->b_page_count * PAGE_SIZE);
 }
 
 /*
@@ -272,51 +269,30 @@ _xfs_buf_alloc(
 	return 0;
 }
 
-/*
- *	Allocate a page array capable of holding a specified number
- *	of pages, and point the page buf at it.
- */
-STATIC int
-_xfs_buf_get_pages(
-	struct xfs_buf		*bp,
-	int			page_count)
+static void
+xfs_buf_free_pages(
+	struct xfs_buf	*bp)
 {
-	/* Make sure that we have a page list */
-	if (bp->b_pages == NULL) {
-		bp->b_page_count = page_count;
-		if (page_count <= XB_PAGES) {
-			bp->b_pages = bp->b_page_array;
-		} else {
-			bp->b_pages = kmem_alloc(sizeof(struct page *) *
-						 page_count, KM_NOFS);
-			if (bp->b_pages == NULL)
-				return -ENOMEM;
-		}
-		memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
+	uint		i;
+
+	ASSERT(bp->b_flags & _XBF_PAGES);
+
+	if (xfs_buf_is_vmapped(bp))
+		vm_unmap_ram(bp->b_addr, bp->b_page_count);
+
+	for (i = 0; i < bp->b_page_count; i++) {
+		if (bp->b_pages[i])
+			__free_page(bp->b_pages[i]);
 	}
-	return 0;
-}
+	if (current->reclaim_state)
+		current->reclaim_state->reclaimed_slab += bp->b_page_count;
 
-/*
- *	Frees b_pages if it was allocated.
- */
-STATIC void
-_xfs_buf_free_pages(
-	struct xfs_buf	*bp)
-{
-	if (bp->b_pages != bp->b_page_array) {
+	if (bp->b_pages != bp->b_page_array)
 		kmem_free(bp->b_pages);
-		bp->b_pages = NULL;
-	}
+	bp->b_pages = NULL;
+	bp->b_flags &= ~_XBF_PAGES;
 }
 
-/*
- *	Releases the specified buffer.
- *
- * 	The modification state of any associated pages is left unchanged.
- * 	The buffer must not be on any hash - use xfs_buf_rele instead for
- * 	hashed and refcounted buffers
- */
 static void
 xfs_buf_free(
 	struct xfs_buf		*bp)
@@ -325,137 +301,103 @@ xfs_buf_free(
 
 	ASSERT(list_empty(&bp->b_lru));
 
-	if (bp->b_flags & _XBF_PAGES) {
-		uint		i;
-
-		if (xfs_buf_is_vmapped(bp))
-			vm_unmap_ram(bp->b_addr - bp->b_offset,
-					bp->b_page_count);
-
-		for (i = 0; i < bp->b_page_count; i++) {
-			struct page	*page = bp->b_pages[i];
-
-			__free_page(page);
-		}
-		if (current->reclaim_state)
-			current->reclaim_state->reclaimed_slab +=
-							bp->b_page_count;
-	} else if (bp->b_flags & _XBF_KMEM)
+	if (bp->b_flags & _XBF_PAGES)
+		xfs_buf_free_pages(bp);
+	else if (bp->b_flags & _XBF_KMEM)
 		kmem_free(bp->b_addr);
-	_xfs_buf_free_pages(bp);
+
 	xfs_buf_free_maps(bp);
 	kmem_cache_free(xfs_buf_zone, bp);
 }
 
-/*
- * Allocates all the pages for buffer in question and builds it's page list.
- */
-STATIC int
-xfs_buf_allocate_memory(
-	struct xfs_buf		*bp,
-	uint			flags)
+static int
+xfs_buf_alloc_kmem(
+	struct xfs_buf	*bp,
+	xfs_buf_flags_t	flags)
 {
-	size_t			size;
-	size_t			nbytes, offset;
-	gfp_t			gfp_mask = xb_to_gfp(flags);
-	unsigned short		page_count, i;
-	xfs_off_t		start, end;
-	int			error;
-	xfs_km_flags_t		kmflag_mask = 0;
+	int		align_mask = xfs_buftarg_dma_alignment(bp->b_target);
+	xfs_km_flags_t	kmflag_mask = KM_NOFS;
+	size_t		size = BBTOB(bp->b_length);
 
-	/*
-	 * assure zeroed buffer for non-read cases.
-	 */
-	if (!(flags & XBF_READ)) {
+	/* Assure zeroed buffer for non-read cases. */
+	if (!(flags & XBF_READ))
 		kmflag_mask |= KM_ZERO;
-		gfp_mask |= __GFP_ZERO;
-	}
 
-	/*
-	 * for buffers that are contained within a single page, just allocate
-	 * the memory from the heap - there's no need for the complexity of
-	 * page arrays to keep allocation down to order 0.
-	 */
-	size = BBTOB(bp->b_length);
-	if (size < PAGE_SIZE) {
-		int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
-		bp->b_addr = kmem_alloc_io(size, align_mask,
-					   KM_NOFS | kmflag_mask);
-		if (!bp->b_addr) {
-			/* low memory - use alloc_page loop instead */
-			goto use_alloc_page;
-		}
+	bp->b_addr = kmem_alloc_io(size, align_mask, kmflag_mask);
+	if (!bp->b_addr)
+		return -ENOMEM;
 
-		if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
-		    ((unsigned long)bp->b_addr & PAGE_MASK)) {
-			/* b_addr spans two pages - use alloc_page instead */
-			kmem_free(bp->b_addr);
-			bp->b_addr = NULL;
-			goto use_alloc_page;
-		}
-		bp->b_offset = offset_in_page(bp->b_addr);
-		bp->b_pages = bp->b_page_array;
-		bp->b_pages[0] = kmem_to_page(bp->b_addr);
-		bp->b_page_count = 1;
-		bp->b_flags |= _XBF_KMEM;
-		return 0;
+	if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
+	    ((unsigned long)bp->b_addr & PAGE_MASK)) {
+		/* b_addr spans two pages - use alloc_page instead */
+		kmem_free(bp->b_addr);
+		bp->b_addr = NULL;
+		return -ENOMEM;
 	}
+	bp->b_offset = offset_in_page(bp->b_addr);
+	bp->b_pages = bp->b_page_array;
+	bp->b_pages[0] = kmem_to_page(bp->b_addr);
+	bp->b_page_count = 1;
+	bp->b_flags |= _XBF_KMEM;
+	return 0;
+}
 
-use_alloc_page:
-	start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
-	end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
-								>> PAGE_SHIFT;
-	page_count = end - start;
-	error = _xfs_buf_get_pages(bp, page_count);
-	if (unlikely(error))
-		return error;
+static int
+xfs_buf_alloc_pages(
+	struct xfs_buf	*bp,
+	xfs_buf_flags_t	flags)
+{
+	gfp_t		gfp_mask = __GFP_NOWARN;
+	long		filled = 0;
 
-	offset = bp->b_offset;
+	if (flags & XBF_READ_AHEAD)
+		gfp_mask |= __GFP_NORETRY;
+	else
+		gfp_mask |= GFP_NOFS;
+
+	/* Make sure that we have a page list */
+	bp->b_page_count = DIV_ROUND_UP(BBTOB(bp->b_length), PAGE_SIZE);
+	if (bp->b_page_count <= XB_PAGES) {
+		bp->b_pages = bp->b_page_array;
+	} else {
+		bp->b_pages = kzalloc(sizeof(struct page *) * bp->b_page_count,
+					gfp_mask);
+		if (!bp->b_pages)
+			return -ENOMEM;
+	}
 	bp->b_flags |= _XBF_PAGES;
 
-	for (i = 0; i < bp->b_page_count; i++) {
-		struct page	*page;
-		uint		retries = 0;
-retry:
-		page = alloc_page(gfp_mask);
-		if (unlikely(page == NULL)) {
-			if (flags & XBF_READ_AHEAD) {
-				bp->b_page_count = i;
-				error = -ENOMEM;
-				goto out_free_pages;
-			}
+	/* Assure zeroed buffer for non-read cases. */
+	if (!(flags & XBF_READ))
+		gfp_mask |= __GFP_ZERO;
 
-			/*
-			 * This could deadlock.
-			 *
-			 * But until all the XFS lowlevel code is revamped to
-			 * handle buffer allocation failures we can't do much.
-			 */
-			if (!(++retries % 100))
-				xfs_err(NULL,
-		"%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
-					current->comm, current->pid,
-					__func__, gfp_mask);
-
-			XFS_STATS_INC(bp->b_mount, xb_page_retries);
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
-			goto retry;
+	/*
+	 * Bulk filling of pages can take multiple calls. Not filling the entire
+	 * array is not an allocation failure, so don't back off if we get at
+	 * least one extra page.
+	 */
+	for (;;) {
+		long	last = filled;
+
+		filled = alloc_pages_bulk_array(gfp_mask, bp->b_page_count,
+						bp->b_pages);
+		if (filled == bp->b_page_count) {
+			XFS_STATS_INC(bp->b_mount, xb_page_found);
+			break;
 		}
 
-		XFS_STATS_INC(bp->b_mount, xb_page_found);
+		if (filled != last)
+			continue;
+
+		if (flags & XBF_READ_AHEAD) {
+			xfs_buf_free_pages(bp);
+			return -ENOMEM;
+		}
 
-		nbytes = min_t(size_t, size, PAGE_SIZE - offset);
-		size -= nbytes;
-		bp->b_pages[i] = page;
-		offset = 0;
+		XFS_STATS_INC(bp->b_mount, xb_page_retries);
+		congestion_wait(BLK_RW_ASYNC, HZ / 50);
 	}
 	return 0;
-
-out_free_pages:
-	for (i = 0; i < bp->b_page_count; i++)
-		__free_page(bp->b_pages[i]);
-	bp->b_flags &= ~_XBF_PAGES;
-	return error;
 }
 
 /*
@@ -469,7 +411,7 @@ _xfs_buf_map_pages(
 	ASSERT(bp->b_flags & _XBF_PAGES);
 	if (bp->b_page_count == 1) {
 		/* A single page buffer is always mappable */
-		bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
+		bp->b_addr = page_address(bp->b_pages[0]);
 	} else if (flags & XBF_UNMAPPED) {
 		bp->b_addr = NULL;
 	} else {
@@ -496,7 +438,6 @@ _xfs_buf_map_pages(
 
 		if (!bp->b_addr)
 			return -ENOMEM;
-		bp->b_addr += bp->b_offset;
 	}
 
 	return 0;
@@ -720,17 +661,22 @@ xfs_buf_get_map(
 	if (error)
 		return error;
 
-	error = xfs_buf_allocate_memory(new_bp, flags);
-	if (error) {
-		xfs_buf_free(new_bp);
-		return error;
+	/*
+	 * For buffers that fit entirely within a single page, first attempt to
+	 * allocate the memory from the heap to minimise memory usage. If we
+	 * can't get heap memory for these small buffers, we fall back to using
+	 * the page allocator.
+	 */
+	if (BBTOB(new_bp->b_length) >= PAGE_SIZE ||
+	    xfs_buf_alloc_kmem(new_bp, flags) < 0) {
+		error = xfs_buf_alloc_pages(new_bp, flags);
+		if (error)
+			goto out_free_buf;
 	}
 
 	error = xfs_buf_find(target, map, nmaps, flags, new_bp, &bp);
-	if (error) {
-		xfs_buf_free(new_bp);
-		return error;
-	}
+	if (error)
+		goto out_free_buf;
 
 	if (bp != new_bp)
 		xfs_buf_free(new_bp);
@@ -758,6 +704,9 @@ found:
 	trace_xfs_buf_get(bp, flags, _RET_IP_);
 	*bpp = bp;
 	return 0;
+out_free_buf:
+	xfs_buf_free(new_bp);
+	return error;
 }
 
 int
@@ -950,8 +899,7 @@ xfs_buf_get_uncached(
 	int			flags,
 	struct xfs_buf		**bpp)
 {
-	unsigned long		page_count;
-	int			error, i;
+	int			error;
 	struct xfs_buf		*bp;
 	DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
 
@@ -960,41 +908,25 @@ xfs_buf_get_uncached(
 	/* flags might contain irrelevant bits, pass only what we care about */
 	error = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT, &bp);
 	if (error)
-		goto fail;
+		return error;
 
-	page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
-	error = _xfs_buf_get_pages(bp, page_count);
+	error = xfs_buf_alloc_pages(bp, flags);
 	if (error)
 		goto fail_free_buf;
 
-	for (i = 0; i < page_count; i++) {
-		bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
-		if (!bp->b_pages[i]) {
-			error = -ENOMEM;
-			goto fail_free_mem;
-		}
-	}
-	bp->b_flags |= _XBF_PAGES;
-
 	error = _xfs_buf_map_pages(bp, 0);
 	if (unlikely(error)) {
 		xfs_warn(target->bt_mount,
 			"%s: failed to map pages", __func__);
-		goto fail_free_mem;
+		goto fail_free_buf;
 	}
 
 	trace_xfs_buf_get_uncached(bp, _RET_IP_);
 	*bpp = bp;
 	return 0;
 
- fail_free_mem:
-	while (--i >= 0)
-		__free_page(bp->b_pages[i]);
-	_xfs_buf_free_pages(bp);
- fail_free_buf:
-	xfs_buf_free_maps(bp);
-	kmem_cache_free(xfs_buf_zone, bp);
- fail:
+fail_free_buf:
+	xfs_buf_free(bp);
 	return error;
 }
 
@@ -1722,7 +1654,6 @@ xfs_buf_offset(
 	if (bp->b_addr)
 		return bp->b_addr + offset;
 
-	offset += bp->b_offset;
 	page = bp->b_pages[offset >> PAGE_SHIFT];
 	return page_address(page) + (offset & (PAGE_SIZE-1));
 }
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 459ca34f26f5..464dc548fa23 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -167,7 +167,8 @@ struct xfs_buf {
 	atomic_t		b_pin_count;	/* pin count */
 	atomic_t		b_io_remaining;	/* #outstanding I/O requests */
 	unsigned int		b_page_count;	/* size of page array */
-	unsigned int		b_offset;	/* page offset in first page */
+	unsigned int		b_offset;	/* page offset of b_addr,
+						   only for _XBF_KMEM buffers */
 	int			b_error;	/* error code on I/O */
 
 	/*