Merge tag 'reflink-speedups-5.19_2022-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-5.19-for-next

xfs: fix reflink inefficiencies

As Dave Chinner has complained about on IRC, there are a couple of
things about reflink that are very inefficient.  First of all, we
limited the size of all bunmapi operations to avoid flooding the log
with defer ops in the worst case, but recent changes to the defer
ops code have solved that problem, so get rid of the bunmapi length
clamp.

Second, the log reservations for reflink operations are far far
larger than they need to be.  Shrink them to exactly what we need to
handle each deferred RUI and CUI log item, and no more.  Also reduce
logcount because we don't need 8 rolls per operation.  Introduce a
transaction reservation compatibility layer to avoid changing the
minimum log size calculations.

Signed-off-by: Dave Chinner <david@fromorbit.com>

9 files changed, 345 insertions, 139 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 24462bdfd8e7..6833110d1bd4 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5280,7 +5280,6 @@ __xfs_bunmapi(
 	int			whichfork;	/* data or attribute fork */
 	xfs_fsblock_t		sum;
 	xfs_filblks_t		len = *rlen;	/* length to unmap in file */
-	xfs_fileoff_t		max_len;
 	xfs_fileoff_t		end;
 	struct xfs_iext_cursor	icur;
 	bool			done = false;
@@ -5299,16 +5298,6 @@ __xfs_bunmapi(
 	ASSERT(len > 0);
 	ASSERT(nexts >= 0);
 
-	/*
-	 * Guesstimate how many blocks we can unmap without running the risk of
-	 * blowing out the transaction with a mix of EFIs and reflink
-	 * adjustments.
-	 */
-	if (tp && xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK)
-		max_len = min(len, xfs_refcount_max_unmap(tp->t_log_res));
-	else
-		max_len = len;
-
 	error = xfs_iread_extents(tp, ip, whichfork);
 	if (error)
 		return error;
@@ -5347,7 +5336,7 @@ __xfs_bunmapi(
 
 	extno = 0;
 	while (end != (xfs_fileoff_t)-1 && end >= start &&
-	       (nexts == 0 || extno < nexts) && max_len > 0) {
+	       (nexts == 0 || extno < nexts)) {
 		/*
 		 * Is the found extent after a hole in which end lives?
 		 * Just back up to the previous extent, if so.
@@ -5381,14 +5370,6 @@ __xfs_bunmapi(
 		if (del.br_startoff + del.br_blockcount > end + 1)
 			del.br_blockcount = end + 1 - del.br_startoff;
 
-		/* How much can we safely unmap? */
-		if (max_len < del.br_blockcount) {
-			del.br_startoff += del.br_blockcount - max_len;
-			if (!wasdel)
-				del.br_startblock += del.br_blockcount - max_len;
-			del.br_blockcount = max_len;
-		}
-
 		if (!isrt)
 			goto delete;
 
@@ -5524,7 +5505,6 @@ delete:
 		if (error)
 			goto error0;
 
-		max_len -= del.br_blockcount;
 		end = del.br_startoff - 1;
 nodelete:
 		/*
diff --git a/fs/xfs/libxfs/xfs_log_rlimit.c b/fs/xfs/libxfs/xfs_log_rlimit.c
index 67798ff5e14e..9975b93a7412 100644
--- a/fs/xfs/libxfs/xfs_log_rlimit.c
+++ b/fs/xfs/libxfs/xfs_log_rlimit.c
@@ -14,6 +14,7 @@
 #include "xfs_trans_space.h"
 #include "xfs_da_btree.h"
 #include "xfs_bmap_btree.h"
+#include "xfs_trace.h"
 
 /*
  * Calculate the maximum length in bytes that would be required for a local
@@ -37,6 +38,65 @@ xfs_log_calc_max_attrsetm_res(
 }
 
 /*
+ * Compute an alternate set of log reservation sizes for use exclusively with
+ * minimum log size calculations.
+ */
+static void
+xfs_log_calc_trans_resv_for_minlogblocks(
+	struct xfs_mount	*mp,
+	struct xfs_trans_resv	*resv)
+{
+	unsigned int		rmap_maxlevels = mp->m_rmap_maxlevels;
+
+	/*
+	 * In the early days of rmap+reflink, we always set the rmap maxlevels
+	 * to 9 even if the AG was small enough that it would never grow to
+	 * that height.  Transaction reservation sizes influence the minimum
+	 * log size calculation, which influences the size of the log that mkfs
+	 * creates.  Use the old value here to ensure that newly formatted
+	 * small filesystems will mount on older kernels.
+	 */
+	if (xfs_has_rmapbt(mp) && xfs_has_reflink(mp))
+		mp->m_rmap_maxlevels = XFS_OLD_REFLINK_RMAP_MAXLEVELS;
+
+	xfs_trans_resv_calc(mp, resv);
+
+	if (xfs_has_reflink(mp)) {
+		/*
+		 * In the early days of reflink, typical log operation counts
+		 * were greatly overestimated.
+		 */
+		resv->tr_write.tr_logcount = XFS_WRITE_LOG_COUNT_REFLINK;
+		resv->tr_itruncate.tr_logcount =
+				XFS_ITRUNCATE_LOG_COUNT_REFLINK;
+		resv->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT_REFLINK;
+	} else if (xfs_has_rmapbt(mp)) {
+		/*
+		 * In the early days of non-reflink rmap, the impact of rmapbt
+		 * updates on log counts were not taken into account at all.
+		 */
+		resv->tr_write.tr_logcount = XFS_WRITE_LOG_COUNT;
+		resv->tr_itruncate.tr_logcount = XFS_ITRUNCATE_LOG_COUNT;
+		resv->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT;
+	}
+
+	/*
+	 * In the early days of reflink, we did not use deferred refcount
+	 * update log items, so log reservations must be recomputed using the
+	 * old calculations.
+	 */
+	resv->tr_write.tr_logres =
+			xfs_calc_write_reservation_minlogsize(mp);
+	resv->tr_itruncate.tr_logres =
+			xfs_calc_itruncate_reservation_minlogsize(mp);
+	resv->tr_qm_dqalloc.tr_logres =
+			xfs_calc_qm_dqalloc_reservation_minlogsize(mp);
+
+	/* Put everything back the way it was.  This goes at the end. */
+	mp->m_rmap_maxlevels = rmap_maxlevels;
+}
+
+/*
  * Iterate over the log space reservation table to figure out and return
  * the maximum one in terms of the pre-calculated values which were done
  * at mount time.
@@ -46,19 +106,25 @@ xfs_log_get_max_trans_res(
 	struct xfs_mount	*mp,
 	struct xfs_trans_res	*max_resp)
 {
+	struct xfs_trans_resv	resv = {};
 	struct xfs_trans_res	*resp;
 	struct xfs_trans_res	*end_resp;
+	unsigned int		i;
 	int			log_space = 0;
 	int			attr_space;
 
 	attr_space = xfs_log_calc_max_attrsetm_res(mp);
 
-	resp = (struct xfs_trans_res *)M_RES(mp);
-	end_resp = (struct xfs_trans_res *)(M_RES(mp) + 1);
-	for (; resp < end_resp; resp++) {
+	xfs_log_calc_trans_resv_for_minlogblocks(mp, &resv);
+
+	resp = (struct xfs_trans_res *)&resv;
+	end_resp = (struct xfs_trans_res *)(&resv + 1);
+	for (i = 0; resp < end_resp; i++, resp++) {
 		int		tmp = resp->tr_logcount > 1 ?
 				      resp->tr_logres * resp->tr_logcount :
 				      resp->tr_logres;
+
+		trace_xfs_trans_resv_calc_minlogsize(mp, i, resp);
 		if (log_space < tmp) {
 			log_space = tmp;
 			*max_resp = *resp;		/* struct copy */
@@ -66,9 +132,10 @@ xfs_log_get_max_trans_res(
 	}
 
 	if (attr_space > log_space) {
-		*max_resp = M_RES(mp)->tr_attrsetm;	/* struct copy */
+		*max_resp = resv.tr_attrsetm;	/* struct copy */
 		max_resp->tr_logres = attr_space;
 	}
+	trace_xfs_log_get_max_trans_res(mp, max_resp);
 }
 
 /*
diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
index 327ba25e9e17..97e9e6020596 100644
--- a/fs/xfs/libxfs/xfs_refcount.c
+++ b/fs/xfs/libxfs/xfs_refcount.c
@@ -886,8 +886,13 @@ xfs_refcount_still_have_space(
 {
 	unsigned long			overhead;
 
-	overhead = cur->bc_ag.refc.shape_changes *
-			xfs_allocfree_log_count(cur->bc_mp, 1);
+	/*
+	 * Worst case estimate: full splits of the free space and rmap btrees
+	 * to handle each of the shape changes to the refcount btree.
+	 */
+	overhead = xfs_allocfree_block_count(cur->bc_mp,
+				cur->bc_ag.refc.shape_changes);
+	overhead += cur->bc_mp->m_refc_maxlevels;
 	overhead *= cur->bc_mp->m_sb.sb_blocksize;
 
 	/*
@@ -960,6 +965,7 @@ xfs_refcount_adjust_extents(
 			 * Either cover the hole (increment) or
 			 * delete the range (decrement).
 			 */
+			cur->bc_ag.refc.nr_ops++;
 			if (tmp.rc_refcount) {
 				error = xfs_refcount_insert(cur, &tmp,
 						&found_tmp);
@@ -970,7 +976,6 @@ xfs_refcount_adjust_extents(
 					error = -EFSCORRUPTED;
 					goto out_error;
 				}
-				cur->bc_ag.refc.nr_ops++;
 			} else {
 				fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
 						cur->bc_ag.pag->pag_agno,
@@ -1001,11 +1006,11 @@ xfs_refcount_adjust_extents(
 		ext.rc_refcount += adj;
 		trace_xfs_refcount_modify_extent(cur->bc_mp,
 				cur->bc_ag.pag->pag_agno, &ext);
+		cur->bc_ag.refc.nr_ops++;
 		if (ext.rc_refcount > 1) {
 			error = xfs_refcount_update(cur, &ext);
 			if (error)
 				goto out_error;
-			cur->bc_ag.refc.nr_ops++;
 		} else if (ext.rc_refcount == 1) {
 			error = xfs_refcount_delete(cur, &found_rec);
 			if (error)
@@ -1014,7 +1019,6 @@ xfs_refcount_adjust_extents(
 				error = -EFSCORRUPTED;
 				goto out_error;
 			}
-			cur->bc_ag.refc.nr_ops++;
 			goto advloop;
 		} else {
 			fsbno = XFS_AGB_TO_FSB(cur->bc_mp,
diff --git a/fs/xfs/libxfs/xfs_refcount.h b/fs/xfs/libxfs/xfs_refcount.h
index 9eb01edbd89d..e8b322de7f3d 100644
--- a/fs/xfs/libxfs/xfs_refcount.h
+++ b/fs/xfs/libxfs/xfs_refcount.h
@@ -67,14 +67,17 @@ extern int xfs_refcount_recover_cow_leftovers(struct xfs_mount *mp,
  * log (plus any key updates) so we'll conservatively assume 32 bytes
  * per record.  We must also leave space for btree splits on both ends
  * of the range and space for the CUD and a new CUI.
+ *
+ * Each EFI that we attach to the transaction is assumed to consume ~32 bytes.
+ * This is a low estimate for an EFI tracking a single extent (16 bytes for the
+ * EFI header, 16 for the extent, and 12 for the xlog op header), but the
+ * estimate is acceptable if there's more than one extent being freed.
+ * In the worst case of freeing every other block during a refcount decrease
+ * operation, we amortize the space used for one EFI log item across 16
+ * extents.
  */
 #define XFS_REFCOUNT_ITEM_OVERHEAD	32
 
-static inline xfs_fileoff_t xfs_refcount_max_unmap(int log_res)
-{
-	return (log_res * 3 / 4) / XFS_REFCOUNT_ITEM_OVERHEAD;
-}
-
 extern int xfs_refcount_has_record(struct xfs_btree_cur *cur,
 		xfs_agblock_t bno, xfs_extlen_t len, bool *exists);
 union xfs_btree_rec;
diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index 8e1d09e8cc9a..e9913c2c5a24 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -56,15 +56,14 @@ xfs_calc_buf_res(
  * Per-extent log reservation for the btree changes involved in freeing or
  * allocating an extent.  In classic XFS there were two trees that will be
  * modified (bnobt + cntbt).  With rmap enabled, there are three trees
- * (rmapbt).  With reflink, there are four trees (refcountbt).  The number of
- * blocks reserved is based on the formula:
+ * (rmapbt).  The number of blocks reserved is based on the formula:
  *
  * num trees * ((2 blocks/level * max depth) - 1)
  *
  * Keep in mind that max depth is calculated separately for each type of tree.
  */
 uint
-xfs_allocfree_log_count(
+xfs_allocfree_block_count(
 	struct xfs_mount *mp,
 	uint		num_ops)
 {
@@ -73,13 +72,24 @@ xfs_allocfree_log_count(
 	blocks = num_ops * 2 * (2 * mp->m_alloc_maxlevels - 1);
 	if (xfs_has_rmapbt(mp))
 		blocks += num_ops * (2 * mp->m_rmap_maxlevels - 1);
-	if (xfs_has_reflink(mp))
-		blocks += num_ops * (2 * mp->m_refc_maxlevels - 1);
 
 	return blocks;
 }
 
 /*
+ * Per-extent log reservation for refcount btree changes.  These are never done
+ * in the same transaction as an allocation or a free, so we compute them
+ * separately.
+ */
+static unsigned int
+xfs_refcountbt_block_count(
+	struct xfs_mount	*mp,
+	unsigned int		num_ops)
+{
+	return num_ops * (2 * mp->m_refc_maxlevels - 1);
+}
+
+/*
  * Logging inodes is really tricksy. They are logged in memory format,
  * which means that what we write into the log doesn't directly translate into
  * the amount of space they use on disk.
@@ -136,7 +146,7 @@ xfs_calc_inobt_res(
 {
 	return xfs_calc_buf_res(M_IGEO(mp)->inobt_maxlevels,
 			XFS_FSB_TO_B(mp, 1)) +
-				xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+				xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 			XFS_FSB_TO_B(mp, 1));
 }
 
@@ -183,7 +193,7 @@ xfs_calc_inode_chunk_res(
 {
 	uint			res, size = 0;
 
-	res = xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+	res = xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 			       XFS_FSB_TO_B(mp, 1));
 	if (alloc) {
 		/* icreate tx uses ordered buffers */
@@ -203,7 +213,7 @@ xfs_calc_inode_chunk_res(
  * extents, as well as the realtime summary block.
  */
 static unsigned int
-xfs_rtalloc_log_count(
+xfs_rtalloc_block_count(
 	struct xfs_mount	*mp,
 	unsigned int		num_ops)
 {
@@ -233,6 +243,28 @@ xfs_rtalloc_log_count(
  * register overflow from temporaries in the calculations.
  */
 
+/*
+ * Compute the log reservation required to handle the refcount update
+ * transaction.  Refcount updates are always done via deferred log items.
+ *
+ * This is calculated as:
+ * Data device refcount updates (t1):
+ *    the agfs of the ags containing the blocks: nr_ops * sector size
+ *    the refcount btrees: nr_ops * 1 trees * (2 * max depth - 1) * block size
+ */
+static unsigned int
+xfs_calc_refcountbt_reservation(
+	struct xfs_mount	*mp,
+	unsigned int		nr_ops)
+{
+	unsigned int		blksz = XFS_FSB_TO_B(mp, 1);
+
+	if (!xfs_has_reflink(mp))
+		return 0;
+
+	return xfs_calc_buf_res(nr_ops, mp->m_sb.sb_sectsize) +
+	       xfs_calc_buf_res(xfs_refcountbt_block_count(mp, nr_ops), blksz);
+}
 
 /*
  * In a write transaction we can allocate a maximum of 2
@@ -255,34 +287,65 @@ xfs_rtalloc_log_count(
  *    the agfls of the ags containing the blocks: 2 * sector size
  *    the super block free block counter: sector size
  *    the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size
+ * And any refcount updates that happen in a separate transaction (t4).
  */
 STATIC uint
 xfs_calc_write_reservation(
-	struct xfs_mount	*mp)
+	struct xfs_mount	*mp,
+	bool			for_minlogsize)
 {
-	unsigned int		t1, t2, t3;
+	unsigned int		t1, t2, t3, t4;
 	unsigned int		blksz = XFS_FSB_TO_B(mp, 1);
 
 	t1 = xfs_calc_inode_res(mp, 1) +
 	     xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK), blksz) +
 	     xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
+	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2), blksz);
 
 	if (xfs_has_realtime(mp)) {
 		t2 = xfs_calc_inode_res(mp, 1) +
 		     xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK),
 				     blksz) +
 		     xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 1), blksz) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1), blksz);
+		     xfs_calc_buf_res(xfs_rtalloc_block_count(mp, 1), blksz) +
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1), blksz);
 	} else {
 		t2 = 0;
 	}
 
 	t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
+	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2), blksz);
 
-	return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
+	/*
+	 * In the early days of reflink, we included enough reservation to log
+	 * two refcountbt splits for each transaction.  The codebase runs
+	 * refcountbt updates in separate transactions now, so to compute the
+	 * minimum log size, add the refcountbtree splits back to t1 and t3 and
+	 * do not account them separately as t4.  Reflink did not support
+	 * realtime when the reservations were established, so no adjustment to
+	 * t2 is needed.
+	 */
+	if (for_minlogsize) {
+		unsigned int	adj = 0;
+
+		if (xfs_has_reflink(mp))
+			adj = xfs_calc_buf_res(
+					xfs_refcountbt_block_count(mp, 2),
+					blksz);
+		t1 += adj;
+		t3 += adj;
+		return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
+	}
+
+	t4 = xfs_calc_refcountbt_reservation(mp, 1);
+	return XFS_DQUOT_LOGRES(mp) + max(t4, max3(t1, t2, t3));
+}
+
+unsigned int
+xfs_calc_write_reservation_minlogsize(
+	struct xfs_mount	*mp)
+{
+	return xfs_calc_write_reservation(mp, true);
 }
 
 /*
@@ -304,29 +367,57 @@ xfs_calc_write_reservation(
  *    the realtime summary: 2 exts * 1 block
  *    worst case split in allocation btrees per extent assuming 2 extents:
  *		2 exts * 2 trees * (2 * max depth - 1) * block size
+ * And any refcount updates that happen in a separate transaction (t4).
  */
 STATIC uint
 xfs_calc_itruncate_reservation(
-	struct xfs_mount	*mp)
+	struct xfs_mount	*mp,
+	bool			for_minlogsize)
 {
-	unsigned int		t1, t2, t3;
+	unsigned int		t1, t2, t3, t4;
 	unsigned int		blksz = XFS_FSB_TO_B(mp, 1);
 
 	t1 = xfs_calc_inode_res(mp, 1) +
 	     xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1, blksz);
 
 	t2 = xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) +
-	     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4), blksz);
+	     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 4), blksz);
 
 	if (xfs_has_realtime(mp)) {
 		t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 2), blksz) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz);
+		     xfs_calc_buf_res(xfs_rtalloc_block_count(mp, 2), blksz) +
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2), blksz);
 	} else {
 		t3 = 0;
 	}
 
-	return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
+	/*
+	 * In the early days of reflink, we included enough reservation to log
+	 * four refcountbt splits in the same transaction as bnobt/cntbt
+	 * updates.  The codebase runs refcountbt updates in separate
+	 * transactions now, so to compute the minimum log size, add the
+	 * refcount btree splits back here and do not compute them separately
+	 * as t4.  Reflink did not support realtime when the reservations were
+	 * established, so do not adjust t3.
+	 */
+	if (for_minlogsize) {
+		if (xfs_has_reflink(mp))
+			t2 += xfs_calc_buf_res(
+					xfs_refcountbt_block_count(mp, 4),
+					blksz);
+
+		return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3);
+	}
+
+	t4 = xfs_calc_refcountbt_reservation(mp, 2);
+	return XFS_DQUOT_LOGRES(mp) + max(t4, max3(t1, t2, t3));
+}
+
+unsigned int
+xfs_calc_itruncate_reservation_minlogsize(
+	struct xfs_mount	*mp)
+{
+	return xfs_calc_itruncate_reservation(mp, true);
 }
 
 /*
@@ -350,7 +441,7 @@ xfs_calc_rename_reservation(
 		     xfs_calc_buf_res(2 * XFS_DIROP_LOG_COUNT(mp),
 				      XFS_FSB_TO_B(mp, 1))),
 		    (xfs_calc_buf_res(7, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 3),
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 3),
 				      XFS_FSB_TO_B(mp, 1))));
 }
 
@@ -390,7 +481,7 @@ xfs_calc_link_reservation(
 		     xfs_calc_buf_res(XFS_DIROP_LOG_COUNT(mp),
 				      XFS_FSB_TO_B(mp, 1))),
 		    (xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 				      XFS_FSB_TO_B(mp, 1))));
 }
 
@@ -428,7 +519,7 @@ xfs_calc_remove_reservation(
 		     xfs_calc_buf_res(XFS_DIROP_LOG_COUNT(mp),
 				      XFS_FSB_TO_B(mp, 1))),
 		    (xfs_calc_buf_res(4, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2),
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2),
 				      XFS_FSB_TO_B(mp, 1))));
 }
 
@@ -573,7 +664,7 @@ xfs_calc_growdata_reservation(
 	struct xfs_mount	*mp)
 {
 	return xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +
-		xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+		xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 				 XFS_FSB_TO_B(mp, 1));
 }
 
@@ -595,7 +686,7 @@ xfs_calc_growrtalloc_reservation(
 		xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK),
 				 XFS_FSB_TO_B(mp, 1)) +
 		xfs_calc_inode_res(mp, 1) +
-		xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+		xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 				 XFS_FSB_TO_B(mp, 1));
 }
 
@@ -671,7 +762,7 @@ xfs_calc_addafork_reservation(
 		xfs_calc_buf_res(1, mp->m_dir_geo->blksize) +
 		xfs_calc_buf_res(XFS_DAENTER_BMAP1B(mp, XFS_DATA_FORK) + 1,
 				 XFS_FSB_TO_B(mp, 1)) +
-		xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+		xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1),
 				 XFS_FSB_TO_B(mp, 1));
 }
 
@@ -694,7 +785,7 @@ xfs_calc_attrinval_reservation(
 		    xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK),
 				     XFS_FSB_TO_B(mp, 1))),
 		   (xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) +
-		    xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4),
+		    xfs_calc_buf_res(xfs_allocfree_block_count(mp, 4),
 				     XFS_FSB_TO_B(mp, 1))));
 }
 
@@ -761,7 +852,7 @@ xfs_calc_attrrm_reservation(
 					XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK)) +
 		     xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK), 0)),
 		    (xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) +
-		     xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2),
+		     xfs_calc_buf_res(xfs_allocfree_block_count(mp, 2),
 				      XFS_FSB_TO_B(mp, 1))));
 }
 
@@ -792,13 +883,21 @@ xfs_calc_qm_setqlim_reservation(void)
  */
 STATIC uint
 xfs_calc_qm_dqalloc_reservation(
-	struct xfs_mount	*mp)
+	struct xfs_mount	*mp,
+	bool			for_minlogsize)
 {
-	return xfs_calc_write_reservation(mp) +
+	return xfs_calc_write_reservation(mp, for_minlogsize) +
 		xfs_calc_buf_res(1,
 			XFS_FSB_TO_B(mp, XFS_DQUOT_CLUSTER_SIZE_FSB) - 1);
 }
 
+unsigned int
+xfs_calc_qm_dqalloc_reservation_minlogsize(
+	struct xfs_mount	*mp)
+{
+	return xfs_calc_qm_dqalloc_reservation(mp, true);
+}
+
 /*
  * Syncing the incore super block changes to disk.
  *     the super block to reflect the changes: sector size
@@ -815,36 +914,18 @@ xfs_trans_resv_calc(
 	struct xfs_mount	*mp,
 	struct xfs_trans_resv	*resp)
 {
-	unsigned int		rmap_maxlevels = mp->m_rmap_maxlevels;
-
-	/*
-	 * In the early days of rmap+reflink, we always set the rmap maxlevels
-	 * to 9 even if the AG was small enough that it would never grow to
-	 * that height.  Transaction reservation sizes influence the minimum
-	 * log size calculation, which influences the size of the log that mkfs
-	 * creates.  Use the old value here to ensure that newly formatted
-	 * small filesystems will mount on older kernels.
-	 */
-	if (xfs_has_rmapbt(mp) && xfs_has_reflink(mp))
-		mp->m_rmap_maxlevels = XFS_OLD_REFLINK_RMAP_MAXLEVELS;
+	int			logcount_adj = 0;
 
 	/*
 	 * The following transactions are logged in physical format and
 	 * require a permanent reservation on space.
 	 */
-	resp->tr_write.tr_logres = xfs_calc_write_reservation(mp);
-	if (xfs_has_reflink(mp))
-		resp->tr_write.tr_logcount = XFS_WRITE_LOG_COUNT_REFLINK;
-	else
-		resp->tr_write.tr_logcount = XFS_WRITE_LOG_COUNT;
+	resp->tr_write.tr_logres = xfs_calc_write_reservation(mp, false);
+	resp->tr_write.tr_logcount = XFS_WRITE_LOG_COUNT;
 	resp->tr_write.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
-	resp->tr_itruncate.tr_logres = xfs_calc_itruncate_reservation(mp);
-	if (xfs_has_reflink(mp))
-		resp->tr_itruncate.tr_logcount =
-				XFS_ITRUNCATE_LOG_COUNT_REFLINK;
-	else
-		resp->tr_itruncate.tr_logcount = XFS_ITRUNCATE_LOG_COUNT;
+	resp->tr_itruncate.tr_logres = xfs_calc_itruncate_reservation(mp, false);
+	resp->tr_itruncate.tr_logcount = XFS_ITRUNCATE_LOG_COUNT;
 	resp->tr_itruncate.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
 	resp->tr_rename.tr_logres = xfs_calc_rename_reservation(mp);
@@ -900,11 +981,9 @@ xfs_trans_resv_calc(
 	resp->tr_growrtalloc.tr_logcount = XFS_DEFAULT_PERM_LOG_COUNT;
 	resp->tr_growrtalloc.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
-	resp->tr_qm_dqalloc.tr_logres = xfs_calc_qm_dqalloc_reservation(mp);
-	if (xfs_has_reflink(mp))
-		resp->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT_REFLINK;
-	else
-		resp->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT;
+	resp->tr_qm_dqalloc.tr_logres = xfs_calc_qm_dqalloc_reservation(mp,
+			false);
+	resp->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT;
 	resp->tr_qm_dqalloc.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
 	/*
@@ -931,6 +1010,19 @@ xfs_trans_resv_calc(
 	resp->tr_growrtzero.tr_logres = xfs_calc_growrtzero_reservation(mp);
 	resp->tr_growrtfree.tr_logres = xfs_calc_growrtfree_reservation(mp);
 
-	/* Put everything back the way it was.  This goes at the end. */
-	mp->m_rmap_maxlevels = rmap_maxlevels;
+	/*
+	 * Add one logcount for BUI items that appear with rmap or reflink,
+	 * one logcount for refcount intent items, and one logcount for rmap
+	 * intent items.
+	 */
+	if (xfs_has_reflink(mp) || xfs_has_rmapbt(mp))
+		logcount_adj++;
+	if (xfs_has_reflink(mp))
+		logcount_adj++;
+	if (xfs_has_rmapbt(mp))
+		logcount_adj++;
+
+	resp->tr_itruncate.tr_logcount += logcount_adj;
+	resp->tr_write.tr_logcount += logcount_adj;
+	resp->tr_qm_dqalloc.tr_logcount += logcount_adj;
 }
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index fc4e9b369a3a..0554b9d775d2 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -73,7 +73,6 @@ struct xfs_trans_resv {
 #define	XFS_DEFAULT_LOG_COUNT		1
 #define	XFS_DEFAULT_PERM_LOG_COUNT	2
 #define	XFS_ITRUNCATE_LOG_COUNT		2
-#define	XFS_ITRUNCATE_LOG_COUNT_REFLINK	8
 #define XFS_INACTIVE_LOG_COUNT		2
 #define	XFS_CREATE_LOG_COUNT		2
 #define	XFS_CREATE_TMPFILE_LOG_COUNT	2
@@ -83,13 +82,24 @@ struct xfs_trans_resv {
 #define	XFS_LINK_LOG_COUNT		2
 #define	XFS_RENAME_LOG_COUNT		2
 #define	XFS_WRITE_LOG_COUNT		2
-#define	XFS_WRITE_LOG_COUNT_REFLINK	8
 #define	XFS_ADDAFORK_LOG_COUNT		2
 #define	XFS_ATTRINVAL_LOG_COUNT		1
 #define	XFS_ATTRSET_LOG_COUNT		3
 #define	XFS_ATTRRM_LOG_COUNT		3
 
+/*
+ * Original log operation counts were overestimated in the early days of
+ * reflink.  These are retained here purely for minimum log size calculations
+ * and must not be used for runtime reservations.
+ */
+#define	XFS_ITRUNCATE_LOG_COUNT_REFLINK	8
+#define	XFS_WRITE_LOG_COUNT_REFLINK	8
+
 void xfs_trans_resv_calc(struct xfs_mount *mp, struct xfs_trans_resv *resp);
-uint xfs_allocfree_log_count(struct xfs_mount *mp, uint num_ops);
+uint xfs_allocfree_block_count(struct xfs_mount *mp, uint num_ops);
+
+unsigned int xfs_calc_itruncate_reservation_minlogsize(struct xfs_mount *mp);
+unsigned int xfs_calc_write_reservation_minlogsize(struct xfs_mount *mp);
+unsigned int xfs_calc_qm_dqalloc_reservation_minlogsize(struct xfs_mount *mp);
 
 #endif	/* __XFS_TRANS_RESV_H__ */
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 1ae6d3434ad2..e7a7c00d93be 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -586,21 +586,21 @@ out:
 STATIC int
 xfs_reflink_end_cow_extent(
 	struct xfs_inode	*ip,
-	xfs_fileoff_t		offset_fsb,
-	xfs_fileoff_t		*end_fsb)
+	xfs_fileoff_t		*offset_fsb,
+	xfs_fileoff_t		end_fsb)
 {
-	struct xfs_bmbt_irec	got, del;
 	struct xfs_iext_cursor	icur;
+	struct xfs_bmbt_irec	got, del, data;
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_trans	*tp;
 	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
-	xfs_filblks_t		rlen;
 	unsigned int		resblks;
+	int			nmaps;
 	int			error;
 
 	/* No COW extents?  That's easy! */
 	if (ifp->if_bytes == 0) {
-		*end_fsb = offset_fsb;
+		*offset_fsb = end_fsb;
 		return 0;
 	}
 
@@ -631,42 +631,66 @@ xfs_reflink_end_cow_extent(
 	 * left by the time I/O completes for the loser of the race.  In that
 	 * case we are done.
 	 */
-	if (!xfs_iext_lookup_extent_before(ip, ifp, end_fsb, &icur, &got) ||
-	    got.br_startoff + got.br_blockcount <= offset_fsb) {
-		*end_fsb = offset_fsb;
+	if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
+	    got.br_startoff >= end_fsb) {
+		*offset_fsb = end_fsb;
 		goto out_cancel;
 	}
 
 	/*
-	 * Structure copy @got into @del, then trim @del to the range that we
-	 * were asked to remap.  We preserve @got for the eventual CoW fork
-	 * deletion; from now on @del represents the mapping that we're
-	 * actually remapping.
-	 */
-	del = got;
-	xfs_trim_extent(&del, offset_fsb, *end_fsb - offset_fsb);
-
-	ASSERT(del.br_blockcount > 0);
-
-	/*
 	 * Only remap real extents that contain data.  With AIO, speculative
 	 * preallocations can leak into the range we are called upon, and we
-	 * need to skip them.
+	 * need to skip them.  Preserve @got for the eventual CoW fork
+	 * deletion; from now on @del represents the mapping that we're
+	 * actually remapping.
 	 */
-	if (!xfs_bmap_is_written_extent(&got)) {
-		*end_fsb = del.br_startoff;
-		goto out_cancel;
+	while (!xfs_bmap_is_written_extent(&got)) {
+		if (!xfs_iext_next_extent(ifp, &icur, &got) ||
+		    got.br_startoff >= end_fsb) {
+			*offset_fsb = end_fsb;
+			goto out_cancel;
+		}
 	}
+	del = got;
 
-	/* Unmap the old blocks in the data fork. */
-	rlen = del.br_blockcount;
-	error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1);
+	/* Grab the corresponding mapping in the data fork. */
+	nmaps = 1;
+	error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
+			&nmaps, 0);
 	if (error)
 		goto out_cancel;
 
-	/* Trim the extent to whatever got unmapped. */
-	xfs_trim_extent(&del, del.br_startoff + rlen, del.br_blockcount - rlen);
-	trace_xfs_reflink_cow_remap(ip, &del);
+	/* We can only remap the smaller of the two extent sizes. */
+	data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
+	del.br_blockcount = data.br_blockcount;
+
+	trace_xfs_reflink_cow_remap_from(ip, &del);
+	trace_xfs_reflink_cow_remap_to(ip, &data);
+
+	if (xfs_bmap_is_real_extent(&data)) {
+		/*
+		 * If the extent we're remapping is backed by storage (written
+		 * or not), unmap the extent and drop its refcount.
+		 */
+		xfs_bmap_unmap_extent(tp, ip, &data);
+		xfs_refcount_decrease_extent(tp, &data);
+		xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
+				-data.br_blockcount);
+	} else if (data.br_startblock == DELAYSTARTBLOCK) {
+		int		done;
+
+		/*
+		 * If the extent we're remapping is a delalloc reservation,
+		 * we can use the regular bunmapi function to release the
+		 * incore state.  Dropping the delalloc reservation takes care
+		 * of the quota reservation for us.
+		 */
+		error = xfs_bunmapi(NULL, ip, data.br_startoff,
+				data.br_blockcount, 0, 1, &done);
+		if (error)
+			goto out_cancel;
+		ASSERT(done);
+	}
 
 	/* Free the CoW orphan record. */
 	xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
@@ -687,7 +711,7 @@ xfs_reflink_end_cow_extent(
 		return error;
 
 	/* Update the caller about how much progress we made. */
-	*end_fsb = del.br_startoff;
+	*offset_fsb = del.br_startoff + del.br_blockcount;
 	return 0;
 
 out_cancel:
@@ -715,7 +739,7 @@ xfs_reflink_end_cow(
 	end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 
 	/*
-	 * Walk backwards until we're out of the I/O range.  The loop function
+	 * Walk forwards until we've remapped the I/O range.  The loop function
 	 * repeatedly cycles the ILOCK to allocate one transaction per remapped
 	 * extent.
 	 *
@@ -747,7 +771,7 @@ xfs_reflink_end_cow(
 	 * blocks will be remapped.
 	 */
 	while (end_fsb > offset_fsb && !error)
-		error = xfs_reflink_end_cow_extent(ip, offset_fsb, &end_fsb);
+		error = xfs_reflink_end_cow_extent(ip, &offset_fsb, end_fsb);
 
 	if (error)
 		trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
@@ -1138,7 +1162,7 @@ xfs_reflink_remap_extent(
 		xfs_refcount_decrease_extent(tp, &smap);
 		qdelta -= smap.br_blockcount;
 	} else if (smap.br_startblock == DELAYSTARTBLOCK) {
-		xfs_filblks_t	len = smap.br_blockcount;
+		int		done;
 
 		/*
 		 * If the extent we're unmapping is a delalloc reservation,
@@ -1146,10 +1170,11 @@ xfs_reflink_remap_extent(
 		 * incore state.  Dropping the delalloc reservation takes care
 		 * of the quota reservation for us.
 		 */
-		error = __xfs_bunmapi(NULL, ip, smap.br_startoff, &len, 0, 1);
+		error = xfs_bunmapi(NULL, ip, smap.br_startoff,
+				smap.br_blockcount, 0, 1, &done);
 		if (error)
 			goto out_cancel;
-		ASSERT(len == 0);
+		ASSERT(done);
 	}
 
 	/*
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index fe8f4ec98ec6..e19a3f7351be 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3408,7 +3408,8 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_convert_cow);
 
 DEFINE_SIMPLE_IO_EVENT(xfs_reflink_cancel_cow_range);
 DEFINE_SIMPLE_IO_EVENT(xfs_reflink_end_cow);
-DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_remap);
+DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_remap_from);
+DEFINE_INODE_IREC_EVENT(xfs_reflink_cow_remap_to);
 
 DEFINE_INODE_ERROR_EVENT(xfs_reflink_cancel_cow_range_error);
 DEFINE_INODE_ERROR_EVENT(xfs_reflink_end_cow_error);
@@ -3503,7 +3504,7 @@ DEFINE_GETFSMAP_EVENT(xfs_getfsmap_low_key);
 DEFINE_GETFSMAP_EVENT(xfs_getfsmap_high_key);
 DEFINE_GETFSMAP_EVENT(xfs_getfsmap_mapping);
 
-TRACE_EVENT(xfs_trans_resv_calc,
+DECLARE_EVENT_CLASS(xfs_trans_resv_class,
 	TP_PROTO(struct xfs_mount *mp, unsigned int type,
 		 struct xfs_trans_res *res),
 	TP_ARGS(mp, type, res),
@@ -3527,6 +3528,33 @@ TRACE_EVENT(xfs_trans_resv_calc,
 		  __entry->logres,
 		  __entry->logcount,
 		  __entry->logflags)
+)
+
+#define DEFINE_TRANS_RESV_EVENT(name) \
+DEFINE_EVENT(xfs_trans_resv_class, name, \
+	TP_PROTO(struct xfs_mount *mp, unsigned int type, \
+		 struct xfs_trans_res *res), \
+	TP_ARGS(mp, type, res))
+DEFINE_TRANS_RESV_EVENT(xfs_trans_resv_calc);
+DEFINE_TRANS_RESV_EVENT(xfs_trans_resv_calc_minlogsize);
+
+TRACE_EVENT(xfs_log_get_max_trans_res,
+	TP_PROTO(struct xfs_mount *mp, const struct xfs_trans_res *res),
+	TP_ARGS(mp, res),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(uint, logres)
+		__field(int, logcount)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->logres = res->tr_logres;
+		__entry->logcount = res->tr_logcount;
+	),
+	TP_printk("dev %d:%d logres %u logcount %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->logres,
+		  __entry->logcount)
 );
 
 DECLARE_EVENT_CLASS(xfs_trans_class,
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 836ce2beac53..82cf0189c0db 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -32,7 +32,6 @@ static void
 xfs_trans_trace_reservations(
 	struct xfs_mount	*mp)
 {
-	struct xfs_trans_res	resv;
 	struct xfs_trans_res	*res;
 	struct xfs_trans_res	*end_res;
 	int			i;
@@ -41,8 +40,6 @@ xfs_trans_trace_reservations(
 	end_res = (struct xfs_trans_res *)(M_RES(mp) + 1);
 	for (i = 0; res < end_res; i++, res++)
 		trace_xfs_trans_resv_calc(mp, i, res);
-	xfs_log_get_max_trans_res(mp, &resv);
-	trace_xfs_trans_resv_calc(mp, -1, &resv);
 }
 #else
 # define xfs_trans_trace_reservations(mp)