1 files changed, 245 insertions, 346 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 6819b5163e33..a4beb421018a 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -35,14 +35,12 @@
 #include <linux/freezer.h>
 
 #include "xfs_sb.h"
-#include "xfs_inum.h"
 #include "xfs_log.h"
 #include "xfs_ag.h"
 #include "xfs_mount.h"
 #include "xfs_trace.h"
 
 static kmem_zone_t *xfs_buf_zone;
-STATIC int xfsbufd(void *);
 
 static struct workqueue_struct *xfslogd_workqueue;
 
@@ -57,11 +55,7 @@ static struct workqueue_struct *xfslogd_workqueue;
 #endif
 
 #define xb_to_gfp(flags) \
-	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : \
-	  ((flags) & XBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)
-
-#define xb_to_km(flags) \
-	 (((flags) & XBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)
+	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
 
 
 static inline int
@@ -71,11 +65,11 @@ xfs_buf_is_vmapped(
 	/*
 	 * Return true if the buffer is vmapped.
 	 *
-	 * The XBF_MAPPED flag is set if the buffer should be mapped, but the
-	 * code is clever enough to know it doesn't have to map a single page,
-	 * so the check has to be both for XBF_MAPPED and bp->b_page_count > 1.
+	 * b_addr is null if the buffer is not mapped, but the code is clever
+	 * enough to know it doesn't have to map a single page, so the check has
+	 * to be both for b_addr and bp->b_page_count > 1.
 	 */
-	return (bp->b_flags & XBF_MAPPED) && bp->b_page_count > 1;
+	return bp->b_addr && bp->b_page_count > 1;
 }
 
 static inline int
@@ -144,8 +138,17 @@ void
 xfs_buf_stale(
 	struct xfs_buf	*bp)
 {
+	ASSERT(xfs_buf_islocked(bp));
+
 	bp->b_flags |= XBF_STALE;
-	xfs_buf_delwri_dequeue(bp);
+
+	/*
+	 * Clear the delwri status so that a delwri queue walker will not
+	 * flush this buffer to disk now that it is stale. The delwri queue has
+	 * a reference to the buffer, so this is safe to do.
+	 */
+	bp->b_flags &= ~_XBF_DELWRI_Q;
+
 	atomic_set(&(bp)->b_lru_ref, 0);
 	if (!list_empty(&bp->b_lru)) {
 		struct xfs_buftarg *btp = bp->b_target;
@@ -164,22 +167,22 @@ xfs_buf_stale(
 struct xfs_buf *
 xfs_buf_alloc(
 	struct xfs_buftarg	*target,
-	xfs_off_t		range_base,
-	size_t			range_length,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	struct xfs_buf		*bp;
 
-	bp = kmem_zone_alloc(xfs_buf_zone, xb_to_km(flags));
+	bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
 	if (unlikely(!bp))
 		return NULL;
 
 	/*
-	 * We don't want certain flags to appear in b_flags.
+	 * We don't want certain flags to appear in b_flags unless they are
+	 * specifically set by later operations on the buffer.
 	 */
-	flags &= ~(XBF_LOCK|XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);
+	flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
 
-	memset(bp, 0, sizeof(xfs_buf_t));
 	atomic_set(&bp->b_hold, 1);
 	atomic_set(&bp->b_lru_ref, 1);
 	init_completion(&bp->b_iowait);
@@ -189,15 +192,16 @@ xfs_buf_alloc(
 	sema_init(&bp->b_sema, 0); /* held, no waiters */
 	XB_SET_OWNER(bp);
 	bp->b_target = target;
-	bp->b_file_offset = range_base;
+
 	/*
-	 * Set buffer_length and count_desired to the same value initially.
-	 * I/O routines should use count_desired, which will be the same in
+	 * Set length and io_length to the same value initially.
+	 * I/O routines should use io_length, which will be the same in
 	 * most cases but may be reset (e.g. XFS recovery).
 	 */
-	bp->b_buffer_length = bp->b_count_desired = range_length;
+	bp->b_length = numblks;
+	bp->b_io_length = numblks;
 	bp->b_flags = flags;
-	bp->b_bn = XFS_BUF_DADDR_NULL;
+	bp->b_bn = blkno;
 	atomic_set(&bp->b_pin_count, 0);
 	init_waitqueue_head(&bp->b_waiters);
 
@@ -219,13 +223,12 @@ _xfs_buf_get_pages(
 {
 	/* Make sure that we have a page list */
 	if (bp->b_pages == NULL) {
-		bp->b_offset = xfs_buf_poff(bp->b_file_offset);
 		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, xb_to_km(flags));
+						 page_count, KM_NOFS);
 			if (bp->b_pages == NULL)
 				return -ENOMEM;
 		}
@@ -288,11 +291,11 @@ xfs_buf_allocate_memory(
 	xfs_buf_t		*bp,
 	uint			flags)
 {
-	size_t			size = bp->b_count_desired;
+	size_t			size;
 	size_t			nbytes, offset;
 	gfp_t			gfp_mask = xb_to_gfp(flags);
 	unsigned short		page_count, i;
-	xfs_off_t		end;
+	xfs_off_t		start, end;
 	int			error;
 
 	/*
@@ -300,15 +303,15 @@ xfs_buf_allocate_memory(
 	 * the memory from the heap - there's no need for the complexity of
 	 * page arrays to keep allocation down to order 0.
 	 */
-	if (bp->b_buffer_length < PAGE_SIZE) {
-		bp->b_addr = kmem_alloc(bp->b_buffer_length, xb_to_km(flags));
+	size = BBTOB(bp->b_length);
+	if (size < PAGE_SIZE) {
+		bp->b_addr = kmem_alloc(size, KM_NOFS);
 		if (!bp->b_addr) {
 			/* low memory - use alloc_page loop instead */
 			goto use_alloc_page;
 		}
 
-		if (((unsigned long)(bp->b_addr + bp->b_buffer_length - 1) &
-								PAGE_MASK) !=
+		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);
@@ -319,13 +322,14 @@ xfs_buf_allocate_memory(
 		bp->b_pages = bp->b_page_array;
 		bp->b_pages[0] = virt_to_page(bp->b_addr);
 		bp->b_page_count = 1;
-		bp->b_flags |= XBF_MAPPED | _XBF_KMEM;
+		bp->b_flags |= _XBF_KMEM;
 		return 0;
 	}
 
 use_alloc_page:
-	end = bp->b_file_offset + bp->b_buffer_length;
-	page_count = xfs_buf_btoc(end) - xfs_buf_btoct(bp->b_file_offset);
+	start = BBTOB(bp->b_bn) >> PAGE_SHIFT;
+	end = (BBTOB(bp->b_bn + bp->b_length) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	page_count = end - start;
 	error = _xfs_buf_get_pages(bp, page_count, flags);
 	if (unlikely(error))
 		return error;
@@ -388,8 +392,9 @@ _xfs_buf_map_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_flags |= XBF_MAPPED;
-	} else if (flags & XBF_MAPPED) {
+	} else if (flags & XBF_UNMAPPED) {
+		bp->b_addr = NULL;
+	} else {
 		int retried = 0;
 
 		do {
@@ -403,7 +408,6 @@ _xfs_buf_map_pages(
 		if (!bp->b_addr)
 			return -ENOMEM;
 		bp->b_addr += bp->b_offset;
-		bp->b_flags |= XBF_MAPPED;
 	}
 
 	return 0;
@@ -420,29 +424,27 @@ _xfs_buf_map_pages(
  */
 xfs_buf_t *
 _xfs_buf_find(
-	xfs_buftarg_t		*btp,	/* block device target		*/
-	xfs_off_t		ioff,	/* starting offset of range	*/
-	size_t			isize,	/* length of range		*/
+	struct xfs_buftarg	*btp,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags,
 	xfs_buf_t		*new_bp)
 {
-	xfs_off_t		range_base;
-	size_t			range_length;
+	size_t			numbytes;
 	struct xfs_perag	*pag;
 	struct rb_node		**rbp;
 	struct rb_node		*parent;
 	xfs_buf_t		*bp;
 
-	range_base = (ioff << BBSHIFT);
-	range_length = (isize << BBSHIFT);
+	numbytes = BBTOB(numblks);
 
 	/* Check for IOs smaller than the sector size / not sector aligned */
-	ASSERT(!(range_length < (1 << btp->bt_sshift)));
-	ASSERT(!(range_base & (xfs_off_t)btp->bt_smask));
+	ASSERT(!(numbytes < (1 << btp->bt_sshift)));
+	ASSERT(!(BBTOB(blkno) & (xfs_off_t)btp->bt_smask));
 
 	/* get tree root */
 	pag = xfs_perag_get(btp->bt_mount,
-				xfs_daddr_to_agno(btp->bt_mount, ioff));
+				xfs_daddr_to_agno(btp->bt_mount, blkno));
 
 	/* walk tree */
 	spin_lock(&pag->pag_buf_lock);
@@ -453,20 +455,20 @@ _xfs_buf_find(
 		parent = *rbp;
 		bp = rb_entry(parent, struct xfs_buf, b_rbnode);
 
-		if (range_base < bp->b_file_offset)
+		if (blkno < bp->b_bn)
 			rbp = &(*rbp)->rb_left;
-		else if (range_base > bp->b_file_offset)
+		else if (blkno > bp->b_bn)
 			rbp = &(*rbp)->rb_right;
 		else {
 			/*
-			 * found a block offset match. If the range doesn't
+			 * found a block number match. If the range doesn't
 			 * match, the only way this is allowed is if the buffer
 			 * in the cache is stale and the transaction that made
 			 * it stale has not yet committed. i.e. we are
 			 * reallocating a busy extent. Skip this buffer and
 			 * continue searching to the right for an exact match.
 			 */
-			if (bp->b_buffer_length != range_length) {
+			if (bp->b_length != numblks) {
 				ASSERT(bp->b_flags & XBF_STALE);
 				rbp = &(*rbp)->rb_right;
 				continue;
@@ -511,7 +513,7 @@ found:
 	 */
 	if (bp->b_flags & XBF_STALE) {
 		ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
-		bp->b_flags &= XBF_MAPPED | _XBF_KMEM | _XBF_PAGES;
+		bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
 	}
 
 	trace_xfs_buf_find(bp, flags, _RET_IP_);
@@ -526,63 +528,54 @@ found:
  */
 struct xfs_buf *
 xfs_buf_get(
-	xfs_buftarg_t		*target,/* target for buffer		*/
-	xfs_off_t		ioff,	/* starting offset of range	*/
-	size_t			isize,	/* length of range		*/
+	xfs_buftarg_t		*target,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	struct xfs_buf		*bp;
 	struct xfs_buf		*new_bp;
 	int			error = 0;
 
-	bp = _xfs_buf_find(target, ioff, isize, flags, NULL);
+	bp = _xfs_buf_find(target, blkno, numblks, flags, NULL);
 	if (likely(bp))
 		goto found;
 
-	new_bp = xfs_buf_alloc(target, ioff << BBSHIFT, isize << BBSHIFT,
-			       flags);
+	new_bp = xfs_buf_alloc(target, blkno, numblks, flags);
 	if (unlikely(!new_bp))
 		return NULL;
 
-	bp = _xfs_buf_find(target, ioff, isize, flags, new_bp);
-	if (!bp) {
+	error = xfs_buf_allocate_memory(new_bp, flags);
+	if (error) {
 		kmem_zone_free(xfs_buf_zone, new_bp);
 		return NULL;
 	}
 
-	if (bp == new_bp) {
-		error = xfs_buf_allocate_memory(bp, flags);
-		if (error)
-			goto no_buffer;
-	} else
-		kmem_zone_free(xfs_buf_zone, new_bp);
+	bp = _xfs_buf_find(target, blkno, numblks, flags, new_bp);
+	if (!bp) {
+		xfs_buf_free(new_bp);
+		return NULL;
+	}
 
-	/*
-	 * Now we have a workable buffer, fill in the block number so
-	 * that we can do IO on it.
-	 */
-	bp->b_bn = ioff;
-	bp->b_count_desired = bp->b_buffer_length;
+	if (bp != new_bp)
+		xfs_buf_free(new_bp);
+
+	bp->b_io_length = bp->b_length;
 
 found:
-	if (!(bp->b_flags & XBF_MAPPED)) {
+	if (!bp->b_addr) {
 		error = _xfs_buf_map_pages(bp, flags);
 		if (unlikely(error)) {
 			xfs_warn(target->bt_mount,
 				"%s: failed to map pages\n", __func__);
-			goto no_buffer;
+			xfs_buf_relse(bp);
+			return NULL;
 		}
 	}
 
 	XFS_STATS_INC(xb_get);
 	trace_xfs_buf_get(bp, flags, _RET_IP_);
 	return bp;
-
-no_buffer:
-	if (flags & (XBF_LOCK | XBF_TRYLOCK))
-		xfs_buf_unlock(bp);
-	xfs_buf_rele(bp);
-	return NULL;
 }
 
 STATIC int
@@ -590,32 +583,30 @@ _xfs_buf_read(
 	xfs_buf_t		*bp,
 	xfs_buf_flags_t		flags)
 {
-	int			status;
-
-	ASSERT(!(flags & (XBF_DELWRI|XBF_WRITE)));
+	ASSERT(!(flags & XBF_WRITE));
 	ASSERT(bp->b_bn != XFS_BUF_DADDR_NULL);
 
-	bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_DELWRI | XBF_READ_AHEAD);
+	bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
 	bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 
-	status = xfs_buf_iorequest(bp);
-	if (status || bp->b_error || (flags & XBF_ASYNC))
-		return status;
+	xfs_buf_iorequest(bp);
+	if (flags & XBF_ASYNC)
+		return 0;
 	return xfs_buf_iowait(bp);
 }
 
 xfs_buf_t *
 xfs_buf_read(
 	xfs_buftarg_t		*target,
-	xfs_off_t		ioff,
-	size_t			isize,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	xfs_buf_t		*bp;
 
 	flags |= XBF_READ;
 
-	bp = xfs_buf_get(target, ioff, isize, flags);
+	bp = xfs_buf_get(target, blkno, numblks, flags);
 	if (bp) {
 		trace_xfs_buf_read(bp, flags, _RET_IP_);
 
@@ -627,7 +618,8 @@ xfs_buf_read(
 			 * Read ahead call which is already satisfied,
 			 * drop the buffer
 			 */
-			goto no_buffer;
+			xfs_buf_relse(bp);
+			return NULL;
 		} else {
 			/* We do not want read in the flags */
 			bp->b_flags &= ~XBF_READ;
@@ -635,12 +627,6 @@ xfs_buf_read(
 	}
 
 	return bp;
-
- no_buffer:
-	if (flags & (XBF_LOCK | XBF_TRYLOCK))
-		xfs_buf_unlock(bp);
-	xfs_buf_rele(bp);
-	return NULL;
 }
 
 /*
@@ -650,14 +636,14 @@ xfs_buf_read(
 void
 xfs_buf_readahead(
 	xfs_buftarg_t		*target,
-	xfs_off_t		ioff,
-	size_t			isize)
+	xfs_daddr_t		blkno,
+	size_t			numblks)
 {
 	if (bdi_read_congested(target->bt_bdi))
 		return;
 
-	xfs_buf_read(target, ioff, isize,
-		     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD|XBF_DONT_BLOCK);
+	xfs_buf_read(target, blkno, numblks,
+		     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD);
 }
 
 /*
@@ -666,16 +652,15 @@ xfs_buf_readahead(
  */
 struct xfs_buf *
 xfs_buf_read_uncached(
-	struct xfs_mount	*mp,
 	struct xfs_buftarg	*target,
 	xfs_daddr_t		daddr,
-	size_t			length,
+	size_t			numblks,
 	int			flags)
 {
 	xfs_buf_t		*bp;
 	int			error;
 
-	bp = xfs_buf_get_uncached(target, length, flags);
+	bp = xfs_buf_get_uncached(target, numblks, flags);
 	if (!bp)
 		return NULL;
 
@@ -683,9 +668,9 @@ xfs_buf_read_uncached(
 	XFS_BUF_SET_ADDR(bp, daddr);
 	XFS_BUF_READ(bp);
 
-	xfsbdstrat(mp, bp);
+	xfsbdstrat(target->bt_mount, bp);
 	error = xfs_buf_iowait(bp);
-	if (error || bp->b_error) {
+	if (error) {
 		xfs_buf_relse(bp);
 		return NULL;
 	}
@@ -699,7 +684,7 @@ xfs_buf_read_uncached(
 void
 xfs_buf_set_empty(
 	struct xfs_buf		*bp,
-	size_t			len)
+	size_t			numblks)
 {
 	if (bp->b_pages)
 		_xfs_buf_free_pages(bp);
@@ -707,10 +692,9 @@ xfs_buf_set_empty(
 	bp->b_pages = NULL;
 	bp->b_page_count = 0;
 	bp->b_addr = NULL;
-	bp->b_file_offset = 0;
-	bp->b_buffer_length = bp->b_count_desired = len;
+	bp->b_length = numblks;
+	bp->b_io_length = numblks;
 	bp->b_bn = XFS_BUF_DADDR_NULL;
-	bp->b_flags &= ~XBF_MAPPED;
 }
 
 static inline struct page *
@@ -749,7 +733,7 @@ xfs_buf_associate_memory(
 	bp->b_pages = NULL;
 	bp->b_addr = mem;
 
-	rval = _xfs_buf_get_pages(bp, page_count, XBF_DONT_BLOCK);
+	rval = _xfs_buf_get_pages(bp, page_count, 0);
 	if (rval)
 		return rval;
 
@@ -760,9 +744,8 @@ xfs_buf_associate_memory(
 		pageaddr += PAGE_SIZE;
 	}
 
-	bp->b_count_desired = len;
-	bp->b_buffer_length = buflen;
-	bp->b_flags |= XBF_MAPPED;
+	bp->b_io_length = BTOBB(len);
+	bp->b_length = BTOBB(buflen);
 
 	return 0;
 }
@@ -770,17 +753,18 @@ xfs_buf_associate_memory(
 xfs_buf_t *
 xfs_buf_get_uncached(
 	struct xfs_buftarg	*target,
-	size_t			len,
+	size_t			numblks,
 	int			flags)
 {
-	unsigned long		page_count = PAGE_ALIGN(len) >> PAGE_SHIFT;
+	unsigned long		page_count;
 	int			error, i;
 	xfs_buf_t		*bp;
 
-	bp = xfs_buf_alloc(target, 0, len, 0);
+	bp = xfs_buf_alloc(target, XFS_BUF_DADDR_NULL, numblks, 0);
 	if (unlikely(bp == NULL))
 		goto fail;
 
+	page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
 	error = _xfs_buf_get_pages(bp, page_count, 0);
 	if (error)
 		goto fail_free_buf;
@@ -792,7 +776,7 @@ xfs_buf_get_uncached(
 	}
 	bp->b_flags |= _XBF_PAGES;
 
-	error = _xfs_buf_map_pages(bp, XBF_MAPPED);
+	error = _xfs_buf_map_pages(bp, 0);
 	if (unlikely(error)) {
 		xfs_warn(target->bt_mount,
 			"%s: failed to map pages\n", __func__);
@@ -855,7 +839,7 @@ xfs_buf_rele(
 			spin_unlock(&pag->pag_buf_lock);
 		} else {
 			xfs_buf_lru_del(bp);
-			ASSERT(!(bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)));
+			ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
 			rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
 			spin_unlock(&pag->pag_buf_lock);
 			xfs_perag_put(pag);
@@ -915,13 +899,6 @@ xfs_buf_lock(
 	trace_xfs_buf_lock_done(bp, _RET_IP_);
 }
 
-/*
- *	Releases the lock on the buffer object.
- *	If the buffer is marked delwri but is not queued, do so before we
- *	unlock the buffer as we need to set flags correctly.  We also need to
- *	take a reference for the delwri queue because the unlocker is going to
- *	drop their's and they don't know we just queued it.
- */
 void
 xfs_buf_unlock(
 	struct xfs_buf		*bp)
@@ -1008,9 +985,8 @@ xfs_buf_ioerror_alert(
 	const char		*func)
 {
 	xfs_alert(bp->b_target->bt_mount,
-"metadata I/O error: block 0x%llx (\"%s\") error %d buf count %zd",
-		(__uint64_t)XFS_BUF_ADDR(bp), func,
-		bp->b_error, XFS_BUF_COUNT(bp));
+"metadata I/O error: block 0x%llx (\"%s\") error %d numblks %d",
+		(__uint64_t)XFS_BUF_ADDR(bp), func, bp->b_error, bp->b_length);
 }
 
 int
@@ -1019,10 +995,11 @@ xfs_bwrite(
 {
 	int			error;
 
+	ASSERT(xfs_buf_islocked(bp));
+
 	bp->b_flags |= XBF_WRITE;
-	bp->b_flags &= ~(XBF_ASYNC | XBF_READ);
+	bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q);
 
-	xfs_buf_delwri_dequeue(bp);
 	xfs_bdstrat_cb(bp);
 
 	error = xfs_buf_iowait(bp);
@@ -1181,7 +1158,7 @@ _xfs_buf_ioapply(
 	int			rw, map_i, total_nr_pages, nr_pages;
 	struct bio		*bio;
 	int			offset = bp->b_offset;
-	int			size = bp->b_count_desired;
+	int			size = BBTOB(bp->b_io_length);
 	sector_t		sector = bp->b_bn;
 
 	total_nr_pages = bp->b_page_count;
@@ -1229,7 +1206,7 @@ next_chunk:
 			break;
 
 		offset = 0;
-		sector += nbytes >> BBSHIFT;
+		sector += BTOBB(nbytes);
 		size -= nbytes;
 		total_nr_pages--;
 	}
@@ -1248,13 +1225,13 @@ next_chunk:
 	}
 }
 
-int
+void
 xfs_buf_iorequest(
 	xfs_buf_t		*bp)
 {
 	trace_xfs_buf_iorequest(bp, _RET_IP_);
 
-	ASSERT(!(bp->b_flags & XBF_DELWRI));
+	ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
 
 	if (bp->b_flags & XBF_WRITE)
 		xfs_buf_wait_unpin(bp);
@@ -1269,13 +1246,12 @@ xfs_buf_iorequest(
 	_xfs_buf_ioend(bp, 0);
 
 	xfs_buf_rele(bp);
-	return 0;
 }
 
 /*
- *	Waits for I/O to complete on the buffer supplied.
- *	It returns immediately if no I/O is pending.
- *	It returns the I/O error code, if any, or 0 if there was no error.
+ * Waits for I/O to complete on the buffer supplied.  It returns immediately if
+ * no I/O is pending or there is already a pending error on the buffer.  It
+ * returns the I/O error code, if any, or 0 if there was no error.
  */
 int
 xfs_buf_iowait(
@@ -1283,7 +1259,8 @@ xfs_buf_iowait(
 {
 	trace_xfs_buf_iowait(bp, _RET_IP_);
 
-	wait_for_completion(&bp->b_iowait);
+	if (!bp->b_error)
+		wait_for_completion(&bp->b_iowait);
 
 	trace_xfs_buf_iowait_done(bp, _RET_IP_);
 	return bp->b_error;
@@ -1296,7 +1273,7 @@ xfs_buf_offset(
 {
 	struct page		*page;
 
-	if (bp->b_flags & XBF_MAPPED)
+	if (bp->b_addr)
 		return bp->b_addr + offset;
 
 	offset += bp->b_offset;
@@ -1315,27 +1292,30 @@ xfs_buf_iomove(
 	void			*data,	/* data address			*/
 	xfs_buf_rw_t		mode)	/* read/write/zero flag		*/
 {
-	size_t			bend, cpoff, csize;
-	struct page		*page;
+	size_t			bend;
 
 	bend = boff + bsize;
 	while (boff < bend) {
-		page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
-		cpoff = xfs_buf_poff(boff + bp->b_offset);
-		csize = min_t(size_t,
-			      PAGE_SIZE-cpoff, bp->b_count_desired-boff);
+		struct page	*page;
+		int		page_index, page_offset, csize;
+
+		page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
+		page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
+		page = bp->b_pages[page_index];
+		csize = min_t(size_t, PAGE_SIZE - page_offset,
+				      BBTOB(bp->b_io_length) - boff);
 
-		ASSERT(((csize + cpoff) <= PAGE_SIZE));
+		ASSERT((csize + page_offset) <= PAGE_SIZE);
 
 		switch (mode) {
 		case XBRW_ZERO:
-			memset(page_address(page) + cpoff, 0, csize);
+			memset(page_address(page) + page_offset, 0, csize);
 			break;
 		case XBRW_READ:
-			memcpy(data, page_address(page) + cpoff, csize);
+			memcpy(data, page_address(page) + page_offset, csize);
 			break;
 		case XBRW_WRITE:
-			memcpy(page_address(page) + cpoff, data, csize);
+			memcpy(page_address(page) + page_offset, data, csize);
 		}
 
 		boff += csize;
@@ -1435,11 +1415,9 @@ xfs_free_buftarg(
 {
 	unregister_shrinker(&btp->bt_shrinker);
 
-	xfs_flush_buftarg(btp, 1);
 	if (mp->m_flags & XFS_MOUNT_BARRIER)
 		xfs_blkdev_issue_flush(btp);
 
-	kthread_stop(btp->bt_task);
 	kmem_free(btp);
 }
 
@@ -1491,20 +1469,6 @@ xfs_setsize_buftarg(
 	return xfs_setsize_buftarg_flags(btp, blocksize, sectorsize, 1);
 }
 
-STATIC int
-xfs_alloc_delwri_queue(
-	xfs_buftarg_t		*btp,
-	const char		*fsname)
-{
-	INIT_LIST_HEAD(&btp->bt_delwri_queue);
-	spin_lock_init(&btp->bt_delwri_lock);
-	btp->bt_flags = 0;
-	btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd/%s", fsname);
-	if (IS_ERR(btp->bt_task))
-		return PTR_ERR(btp->bt_task);
-	return 0;
-}
-
 xfs_buftarg_t *
 xfs_alloc_buftarg(
 	struct xfs_mount	*mp,
@@ -1527,8 +1491,6 @@ xfs_alloc_buftarg(
 	spin_lock_init(&btp->bt_lru_lock);
 	if (xfs_setsize_buftarg_early(btp, bdev))
 		goto error;
-	if (xfs_alloc_delwri_queue(btp, fsname))
-		goto error;
 	btp->bt_shrinker.shrink = xfs_buftarg_shrink;
 	btp->bt_shrinker.seeks = DEFAULT_SEEKS;
 	register_shrinker(&btp->bt_shrinker);
@@ -1539,125 +1501,52 @@ error:
 	return NULL;
 }
 
-
 /*
- *	Delayed write buffer handling
+ * Add a buffer to the delayed write list.
+ *
+ * This queues a buffer for writeout if it hasn't already been.  Note that
+ * neither this routine nor the buffer list submission functions perform
+ * any internal synchronization.  It is expected that the lists are thread-local
+ * to the callers.
+ *
+ * Returns true if we queued up the buffer, or false if it already had
+ * been on the buffer list.
  */
-void
+bool
 xfs_buf_delwri_queue(
-	xfs_buf_t		*bp)
+	struct xfs_buf		*bp,
+	struct list_head	*list)
 {
-	struct xfs_buftarg	*btp = bp->b_target;
-
-	trace_xfs_buf_delwri_queue(bp, _RET_IP_);
-
+	ASSERT(xfs_buf_islocked(bp));
 	ASSERT(!(bp->b_flags & XBF_READ));
 
-	spin_lock(&btp->bt_delwri_lock);
-	if (!list_empty(&bp->b_list)) {
-		/* if already in the queue, move it to the tail */
-		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
-		list_move_tail(&bp->b_list, &btp->bt_delwri_queue);
-	} else {
-		/* start xfsbufd as it is about to have something to do */
-		if (list_empty(&btp->bt_delwri_queue))
-			wake_up_process(bp->b_target->bt_task);
-
-		atomic_inc(&bp->b_hold);
-		bp->b_flags |= XBF_DELWRI | _XBF_DELWRI_Q | XBF_ASYNC;
-		list_add_tail(&bp->b_list, &btp->bt_delwri_queue);
-	}
-	bp->b_queuetime = jiffies;
-	spin_unlock(&btp->bt_delwri_lock);
-}
-
-void
-xfs_buf_delwri_dequeue(
-	xfs_buf_t		*bp)
-{
-	int			dequeued = 0;
-
-	spin_lock(&bp->b_target->bt_delwri_lock);
-	if ((bp->b_flags & XBF_DELWRI) && !list_empty(&bp->b_list)) {
-		ASSERT(bp->b_flags & _XBF_DELWRI_Q);
-		list_del_init(&bp->b_list);
-		dequeued = 1;
+	/*
+	 * If the buffer is already marked delwri it already is queued up
+	 * by someone else for imediate writeout.  Just ignore it in that
+	 * case.
+	 */
+	if (bp->b_flags & _XBF_DELWRI_Q) {
+		trace_xfs_buf_delwri_queued(bp, _RET_IP_);
+		return false;
 	}
-	bp->b_flags &= ~(XBF_DELWRI|_XBF_DELWRI_Q);
-	spin_unlock(&bp->b_target->bt_delwri_lock);
-
-	if (dequeued)
-		xfs_buf_rele(bp);
-
-	trace_xfs_buf_delwri_dequeue(bp, _RET_IP_);
-}
-
-/*
- * If a delwri buffer needs to be pushed before it has aged out, then promote
- * it to the head of the delwri queue so that it will be flushed on the next
- * xfsbufd run. We do this by resetting the queuetime of the buffer to be older
- * than the age currently needed to flush the buffer. Hence the next time the
- * xfsbufd sees it is guaranteed to be considered old enough to flush.
- */
-void
-xfs_buf_delwri_promote(
-	struct xfs_buf	*bp)
-{
-	struct xfs_buftarg *btp = bp->b_target;
-	long		age = xfs_buf_age_centisecs * msecs_to_jiffies(10) + 1;
 
-	ASSERT(bp->b_flags & XBF_DELWRI);
-	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
+	trace_xfs_buf_delwri_queue(bp, _RET_IP_);
 
 	/*
-	 * Check the buffer age before locking the delayed write queue as we
-	 * don't need to promote buffers that are already past the flush age.
+	 * If a buffer gets written out synchronously or marked stale while it
+	 * is on a delwri list we lazily remove it. To do this, the other party
+	 * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
+	 * It remains referenced and on the list.  In a rare corner case it
+	 * might get readded to a delwri list after the synchronous writeout, in
+	 * which case we need just need to re-add the flag here.
 	 */
-	if (bp->b_queuetime < jiffies - age)
-		return;
-	bp->b_queuetime = jiffies - age;
-	spin_lock(&btp->bt_delwri_lock);
-	list_move(&bp->b_list, &btp->bt_delwri_queue);
-	spin_unlock(&btp->bt_delwri_lock);
-}
-
-/*
- * Move as many buffers as specified to the supplied list
- * idicating if we skipped any buffers to prevent deadlocks.
- */
-STATIC int
-xfs_buf_delwri_split(
-	xfs_buftarg_t	*target,
-	struct list_head *list,
-	unsigned long	age)
-{
-	xfs_buf_t	*bp, *n;
-	int		skipped = 0;
-	int		force;
-
-	force = test_and_clear_bit(XBT_FORCE_FLUSH, &target->bt_flags);
-	INIT_LIST_HEAD(list);
-	spin_lock(&target->bt_delwri_lock);
-	list_for_each_entry_safe(bp, n, &target->bt_delwri_queue, b_list) {
-		ASSERT(bp->b_flags & XBF_DELWRI);
-
-		if (!xfs_buf_ispinned(bp) && xfs_buf_trylock(bp)) {
-			if (!force &&
-			    time_before(jiffies, bp->b_queuetime + age)) {
-				xfs_buf_unlock(bp);
-				break;
-			}
-
-			bp->b_flags &= ~(XBF_DELWRI | _XBF_DELWRI_Q);
-			bp->b_flags |= XBF_WRITE;
-			list_move_tail(&bp->b_list, list);
-			trace_xfs_buf_delwri_split(bp, _RET_IP_);
-		} else
-			skipped++;
+	bp->b_flags |= _XBF_DELWRI_Q;
+	if (list_empty(&bp->b_list)) {
+		atomic_inc(&bp->b_hold);
+		list_add_tail(&bp->b_list, list);
 	}
 
-	spin_unlock(&target->bt_delwri_lock);
-	return skipped;
+	return true;
 }
 
 /*
@@ -1683,99 +1572,109 @@ xfs_buf_cmp(
 	return 0;
 }
 
-STATIC int
-xfsbufd(
-	void		*data)
+static int
+__xfs_buf_delwri_submit(
+	struct list_head	*buffer_list,
+	struct list_head	*io_list,
+	bool			wait)
 {
-	xfs_buftarg_t   *target = (xfs_buftarg_t *)data;
-
-	current->flags |= PF_MEMALLOC;
-
-	set_freezable();
+	struct blk_plug		plug;
+	struct xfs_buf		*bp, *n;
+	int			pinned = 0;
+
+	list_for_each_entry_safe(bp, n, buffer_list, b_list) {
+		if (!wait) {
+			if (xfs_buf_ispinned(bp)) {
+				pinned++;
+				continue;
+			}
+			if (!xfs_buf_trylock(bp))
+				continue;
+		} else {
+			xfs_buf_lock(bp);
+		}
 
-	do {
-		long	age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
-		long	tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
-		struct list_head tmp;
-		struct blk_plug plug;
+		/*
+		 * Someone else might have written the buffer synchronously or
+		 * marked it stale in the meantime.  In that case only the
+		 * _XBF_DELWRI_Q flag got cleared, and we have to drop the
+		 * reference and remove it from the list here.
+		 */
+		if (!(bp->b_flags & _XBF_DELWRI_Q)) {
+			list_del_init(&bp->b_list);
+			xfs_buf_relse(bp);
+			continue;
+		}
 
-		if (unlikely(freezing(current)))
-			try_to_freeze();
+		list_move_tail(&bp->b_list, io_list);
+		trace_xfs_buf_delwri_split(bp, _RET_IP_);
+	}
 
-		/* sleep for a long time if there is nothing to do. */
-		if (list_empty(&target->bt_delwri_queue))
-			tout = MAX_SCHEDULE_TIMEOUT;
-		schedule_timeout_interruptible(tout);
+	list_sort(NULL, io_list, xfs_buf_cmp);
 
-		xfs_buf_delwri_split(target, &tmp, age);
-		list_sort(NULL, &tmp, xfs_buf_cmp);
+	blk_start_plug(&plug);
+	list_for_each_entry_safe(bp, n, io_list, b_list) {
+		bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC);
+		bp->b_flags |= XBF_WRITE;
 
-		blk_start_plug(&plug);
-		while (!list_empty(&tmp)) {
-			struct xfs_buf *bp;
-			bp = list_first_entry(&tmp, struct xfs_buf, b_list);
+		if (!wait) {
+			bp->b_flags |= XBF_ASYNC;
 			list_del_init(&bp->b_list);
-			xfs_bdstrat_cb(bp);
 		}
-		blk_finish_plug(&plug);
-	} while (!kthread_should_stop());
+		xfs_bdstrat_cb(bp);
+	}
+	blk_finish_plug(&plug);
 
-	return 0;
+	return pinned;
 }
 
 /*
- *	Go through all incore buffers, and release buffers if they belong to
- *	the given device. This is used in filesystem error handling to
- *	preserve the consistency of its metadata.
+ * Write out a buffer list asynchronously.
+ *
+ * This will take the @buffer_list, write all non-locked and non-pinned buffers
+ * out and not wait for I/O completion on any of the buffers.  This interface
+ * is only safely useable for callers that can track I/O completion by higher
+ * level means, e.g. AIL pushing as the @buffer_list is consumed in this
+ * function.
  */
 int
-xfs_flush_buftarg(
-	xfs_buftarg_t	*target,
-	int		wait)
+xfs_buf_delwri_submit_nowait(
+	struct list_head	*buffer_list)
 {
-	xfs_buf_t	*bp;
-	int		pincount = 0;
-	LIST_HEAD(tmp_list);
-	LIST_HEAD(wait_list);
-	struct blk_plug plug;
+	LIST_HEAD		(io_list);
+	return __xfs_buf_delwri_submit(buffer_list, &io_list, false);
+}
 
-	flush_workqueue(xfslogd_workqueue);
+/*
+ * Write out a buffer list synchronously.
+ *
+ * This will take the @buffer_list, write all buffers out and wait for I/O
+ * completion on all of the buffers. @buffer_list is consumed by the function,
+ * so callers must have some other way of tracking buffers if they require such
+ * functionality.
+ */
+int
+xfs_buf_delwri_submit(
+	struct list_head	*buffer_list)
+{
+	LIST_HEAD		(io_list);
+	int			error = 0, error2;
+	struct xfs_buf		*bp;
 
-	set_bit(XBT_FORCE_FLUSH, &target->bt_flags);
-	pincount = xfs_buf_delwri_split(target, &tmp_list, 0);
+	__xfs_buf_delwri_submit(buffer_list, &io_list, true);
 
-	/*
-	 * Dropped the delayed write list lock, now walk the temporary list.
-	 * All I/O is issued async and then if we need to wait for completion
-	 * we do that after issuing all the IO.
-	 */
-	list_sort(NULL, &tmp_list, xfs_buf_cmp);
+	/* Wait for IO to complete. */
+	while (!list_empty(&io_list)) {
+		bp = list_first_entry(&io_list, struct xfs_buf, b_list);
 
-	blk_start_plug(&plug);
-	while (!list_empty(&tmp_list)) {
-		bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);
-		ASSERT(target == bp->b_target);
 		list_del_init(&bp->b_list);
-		if (wait) {
-			bp->b_flags &= ~XBF_ASYNC;
-			list_add(&bp->b_list, &wait_list);
-		}
-		xfs_bdstrat_cb(bp);
-	}
-	blk_finish_plug(&plug);
-
-	if (wait) {
-		/* Wait for IO to complete. */
-		while (!list_empty(&wait_list)) {
-			bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
-
-			list_del_init(&bp->b_list);
-			xfs_buf_iowait(bp);
-			xfs_buf_relse(bp);
-		}
+		error2 = xfs_buf_iowait(bp);
+		xfs_buf_relse(bp);
+		if (!error)
+			error = error2;
 	}
 
-	return pincount;
+	return error;
 }
 
 int __init