[PATCH v2 4/9] exfat: add support for multi-cluster allocation

[Namjae Jeon <linkinjeon@kernel.org>]

Currently exfat_map_cluster() allocates and returns only one cluster
at a time even when more clusters are needed. This causes multiple
FAT walks and repeated allocation calls during large sequential writes
or when using iomap for writes. This change exfat_map_cluster() and
exfat_alloc_cluster() to be able to allocate multiple contiguous
clusters.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/dir.c      |  2 +-
 fs/exfat/exfat_fs.h |  2 +-
 fs/exfat/fatent.c   | 26 ++++++++++++++++----------
 fs/exfat/file.c     |  2 +-
 fs/exfat/inode.c    | 23 ++++++-----------------
 fs/exfat/namei.c    |  2 +-
 6 files changed, 26 insertions(+), 31 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index ca9d707220df..37f324399b6b 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -295,7 +295,7 @@ int exfat_alloc_new_dir(struct inode *inode, struct exfat_chain *clu)
 
 	exfat_chain_set(clu, EXFAT_EOF_CLUSTER, 0, ALLOC_NO_FAT_CHAIN);
 
-	ret = exfat_alloc_cluster(inode, 1, clu, IS_DIRSYNC(inode));
+	ret = exfat_alloc_cluster(inode, 1, clu, IS_DIRSYNC(inode), false);
 	if (ret)
 		return ret;
 
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 9c8ab3df7a42..6e7fd6822b01 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -497,7 +497,7 @@ int exfat_clear_volume_dirty(struct super_block *sb);
 	exfat_cluster_walk(sb, (pclu), 1, ALLOC_FAT_CHAIN)
 
 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
-		struct exfat_chain *p_chain, bool sync_bmap);
+		struct exfat_chain *p_chain, bool sync_bmap, bool contig);
 int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain);
 int exfat_ent_get(struct super_block *sb, unsigned int loc,
 		unsigned int *content, struct buffer_head **last);
diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index 45b0b754a2e4..a917c954bd23 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -419,7 +419,7 @@ int exfat_zeroed_cluster(struct inode *dir, unsigned int clu)
 }
 
 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
-		struct exfat_chain *p_chain, bool sync_bmap)
+		struct exfat_chain *p_chain, bool sync_bmap, bool contig)
 {
 	int ret = -ENOSPC;
 	unsigned int total_cnt;
@@ -470,14 +470,20 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 
 	while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) !=
 	       EXFAT_EOF_CLUSTER) {
-		if (new_clu != hint_clu &&
-		    p_chain->flags == ALLOC_NO_FAT_CHAIN) {
-			if (exfat_chain_cont_cluster(sb, p_chain->dir,
-					p_chain->size)) {
-				ret = -EIO;
-				goto free_cluster;
+		if (new_clu != hint_clu) {
+			if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
+				if (exfat_chain_cont_cluster(sb, p_chain->dir,
+							     p_chain->size)) {
+					ret = -EIO;
+					goto free_cluster;
+				}
+				p_chain->flags = ALLOC_FAT_CHAIN;
+			}
+
+			if (contig && p_chain->size > 0) {
+				hint_clu--;
+				goto done;
 			}
-			p_chain->flags = ALLOC_FAT_CHAIN;
 		}
 
 		/* update allocation bitmap */
@@ -507,9 +513,9 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 		last_clu = new_clu;
 
 		if (p_chain->size == num_alloc) {
+done:
 			sbi->clu_srch_ptr = hint_clu;
-			sbi->used_clusters += num_alloc;
-
+			sbi->used_clusters += p_chain->size;
 			mutex_unlock(&sbi->bitmap_lock);
 			return 0;
 		}
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index b7a4964631a0..15b9d6a1766a 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -56,7 +56,7 @@ static int exfat_cont_expand(struct inode *inode, loff_t size)
 	clu.flags = ei->flags;
 
 	ret = exfat_alloc_cluster(inode, new_num_clusters - num_clusters,
-			&clu, inode_needs_sync(inode));
+			&clu, inode_needs_sync(inode), false);
 	if (ret)
 		return ret;
 
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index 1246713567a5..7b09d94ac464 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -137,9 +137,9 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 	unsigned int num_to_be_allocated = 0, num_clusters;
 
 	num_clusters = exfat_bytes_to_cluster(sbi, exfat_ondisk_size(inode));
-
-	if (clu_offset >= num_clusters)
-		num_to_be_allocated = clu_offset - num_clusters + 1;
+	if (clu_offset > num_clusters ||
+	    *count > num_clusters - clu_offset)
+		num_to_be_allocated = clu_offset + *count - num_clusters;
 
 	if (!create && (num_to_be_allocated > 0)) {
 		*clu = EXFAT_EOF_CLUSTER;
@@ -182,7 +182,7 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 		}
 
 		ret = exfat_alloc_cluster(inode, num_to_be_allocated, &new_clu,
-				inode_needs_sync(inode));
+				inode_needs_sync(inode), true);
 		if (ret)
 			return ret;
 
@@ -216,20 +216,9 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
 		}
 
 		*clu = new_clu.dir;
+		*count = new_clu.size;
 
-		inode->i_blocks +=
-			exfat_cluster_to_sectors(sbi, num_to_be_allocated) >> 9;
-
-		/*
-		 * Move *clu pointer along FAT chains (hole care) because the
-		 * caller of this function expect *clu to be the last cluster.
-		 * This only works when num_to_be_allocated >= 2,
-		 * *clu = (the first cluster of the allocated chain) =>
-		 * (the last cluster of ...)
-		 */
-		if (exfat_cluster_walk(sb, clu, num_to_be_allocated - 1, ei->flags))
-			return -EIO;
-		*count = 1;
+		inode->i_blocks += exfat_cluster_to_sectors(sbi, new_clu.size);
 		if (balloc)
 			*balloc = true;
 	}
diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 752fbec9316b..87e55c5c1bf4 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -341,7 +341,7 @@ int exfat_find_empty_entry(struct inode *inode,
 		}
 
 		/* allocate a cluster */
-		ret = exfat_alloc_cluster(inode, 1, &clu, IS_DIRSYNC(inode));
+		ret = exfat_alloc_cluster(inode, 1, &clu, IS_DIRSYNC(inode), false);
 		if (ret)
 			return ret;
 
-- 
2.25.1