[PATCH 06/15] nilfs2: convert persistent object allocator to use kmap_local

[Ryusuke Konishi]

Regarding the allocator code that is commonly used in the ondisk inode
metadata file ifile and the disk address translation metadata file
DAT, convert the parts that use the deprecated kmap_atomic() and kmap()
to use kmap_local.

Most can be converted directly, but only
nilfs_palloc_prepare_alloc_entry() needs to be rewritten to change mapping
sections so that multiple kmap_local/kunmap_local calls are nested and
disk I/O can be avoided within the mapping sections.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
---
 fs/nilfs2/alloc.c | 91 ++++++++++++++++++++++++-----------------------
 1 file changed, 46 insertions(+), 45 deletions(-)

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index 7342de296ec3..89caef7513db 100644
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -525,54 +525,55 @@ int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
 		ret = nilfs_palloc_get_desc_block(inode, group, 1, &desc_bh);
 		if (ret < 0)
 			return ret;
-		desc_kaddr = kmap(desc_bh->b_page);
+		desc_kaddr = kmap_local_page(desc_bh->b_page);
 		desc = nilfs_palloc_block_get_group_desc(
 			inode, group, desc_bh, desc_kaddr);
 		n = nilfs_palloc_rest_groups_in_desc_block(inode, group,
 							   maxgroup);
-		for (j = 0; j < n; j++, desc++, group++) {
+		for (j = 0; j < n; j++, desc++, group++, group_offset = 0) {
 			lock = nilfs_mdt_bgl_lock(inode, group);
-			if (nilfs_palloc_group_desc_nfrees(desc, lock) > 0) {
-				ret = nilfs_palloc_get_bitmap_block(
-					inode, group, 1, &bitmap_bh);
-				if (ret < 0)
-					goto out_desc;
-				bitmap_kaddr = kmap(bitmap_bh->b_page);
-				bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
-				pos = nilfs_palloc_find_available_slot(
-					bitmap, group_offset,
-					entries_per_group, lock);
-				if (pos >= 0) {
-					/* found a free entry */
-					nilfs_palloc_group_desc_add_entries(
-						desc, lock, -1);
-					req->pr_entry_nr =
-						entries_per_group * group + pos;
-					kunmap(desc_bh->b_page);
-					kunmap(bitmap_bh->b_page);
-
-					req->pr_desc_bh = desc_bh;
-					req->pr_bitmap_bh = bitmap_bh;
-					return 0;
-				}
-				kunmap(bitmap_bh->b_page);
-				brelse(bitmap_bh);
+			if (nilfs_palloc_group_desc_nfrees(desc, lock) == 0)
+				continue;
+
+			kunmap_local(desc_kaddr);
+			ret = nilfs_palloc_get_bitmap_block(inode, group, 1,
+							    &bitmap_bh);
+			if (unlikely(ret < 0)) {
+				brelse(desc_bh);
+				return ret;
 			}
 
-			group_offset = 0;
+			desc_kaddr = kmap_local_page(desc_bh->b_page);
+			desc = nilfs_palloc_block_get_group_desc(
+				inode, group, desc_bh, desc_kaddr);
+
+			bitmap_kaddr = kmap_local_page(bitmap_bh->b_page);
+			bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
+			pos = nilfs_palloc_find_available_slot(
+				bitmap, group_offset, entries_per_group, lock);
+			kunmap_local(bitmap_kaddr);
+			if (pos >= 0)
+				goto found;
+
+			brelse(bitmap_bh);
 		}
 
-		kunmap(desc_bh->b_page);
+		kunmap_local(desc_kaddr);
 		brelse(desc_bh);
 	}
 
 	/* no entries left */
 	return -ENOSPC;
 
- out_desc:
-	kunmap(desc_bh->b_page);
-	brelse(desc_bh);
-	return ret;
+found:
+	/* found a free entry */
+	nilfs_palloc_group_desc_add_entries(desc, lock, -1);
+	req->pr_entry_nr = entries_per_group * group + pos;
+	kunmap_local(desc_kaddr);
+
+	req->pr_desc_bh = desc_bh;
+	req->pr_bitmap_bh = bitmap_bh;
+	return 0;
 }
 
 /**
@@ -606,10 +607,10 @@ void nilfs_palloc_commit_free_entry(struct inode *inode,
 	spinlock_t *lock;
 
 	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
-	desc_kaddr = kmap(req->pr_desc_bh->b_page);
+	desc_kaddr = kmap_local_page(req->pr_desc_bh->b_page);
 	desc = nilfs_palloc_block_get_group_desc(inode, group,
 						 req->pr_desc_bh, desc_kaddr);
-	bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
+	bitmap_kaddr = kmap_local_page(req->pr_bitmap_bh->b_page);
 	bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
 	lock = nilfs_mdt_bgl_lock(inode, group);
 
@@ -621,8 +622,8 @@ void nilfs_palloc_commit_free_entry(struct inode *inode,
 	else
 		nilfs_palloc_group_desc_add_entries(desc, lock, 1);
 
-	kunmap(req->pr_bitmap_bh->b_page);
-	kunmap(req->pr_desc_bh->b_page);
+	kunmap_local(bitmap_kaddr);
+	kunmap_local(desc_kaddr);
 
 	mark_buffer_dirty(req->pr_desc_bh);
 	mark_buffer_dirty(req->pr_bitmap_bh);
@@ -647,10 +648,10 @@ void nilfs_palloc_abort_alloc_entry(struct inode *inode,
 	spinlock_t *lock;
 
 	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
-	desc_kaddr = kmap(req->pr_desc_bh->b_page);
+	desc_kaddr = kmap_local_page(req->pr_desc_bh->b_page);
 	desc = nilfs_palloc_block_get_group_desc(inode, group,
 						 req->pr_desc_bh, desc_kaddr);
-	bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
+	bitmap_kaddr = kmap_local_page(req->pr_bitmap_bh->b_page);
 	bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
 	lock = nilfs_mdt_bgl_lock(inode, group);
 
@@ -662,8 +663,8 @@ void nilfs_palloc_abort_alloc_entry(struct inode *inode,
 	else
 		nilfs_palloc_group_desc_add_entries(desc, lock, 1);
 
-	kunmap(req->pr_bitmap_bh->b_page);
-	kunmap(req->pr_desc_bh->b_page);
+	kunmap_local(bitmap_kaddr);
+	kunmap_local(desc_kaddr);
 
 	brelse(req->pr_bitmap_bh);
 	brelse(req->pr_desc_bh);
@@ -755,7 +756,7 @@ int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
 		/* Get the first entry number of the group */
 		group_min_nr = (__u64)group * epg;
 
-		bitmap_kaddr = kmap(bitmap_bh->b_page);
+		bitmap_kaddr = kmap_local_page(bitmap_bh->b_page);
 		bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
 		lock = nilfs_mdt_bgl_lock(inode, group);
 
@@ -801,7 +802,7 @@ int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
 			entry_start = rounddown(group_offset, epb);
 		} while (true);
 
-		kunmap(bitmap_bh->b_page);
+		kunmap_local(bitmap_kaddr);
 		mark_buffer_dirty(bitmap_bh);
 		brelse(bitmap_bh);
 
@@ -815,11 +816,11 @@ int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
 					   inode->i_ino);
 		}
 
-		desc_kaddr = kmap_atomic(desc_bh->b_page);
+		desc_kaddr = kmap_local_page(desc_bh->b_page);
 		desc = nilfs_palloc_block_get_group_desc(
 			inode, group, desc_bh, desc_kaddr);
 		nfree = nilfs_palloc_group_desc_add_entries(desc, lock, n);
-		kunmap_atomic(desc_kaddr);
+		kunmap_local(desc_kaddr);
 		mark_buffer_dirty(desc_bh);
 		nilfs_mdt_mark_dirty(inode);
 		brelse(desc_bh);
-- 
2.34.1