fat: support adding multiple clusters

fat_add_cluster() currently adds only one cluster to a file's chain,
requiring multiple calls when adding more clusters.

Add a fat_alloc_chain() helper that allocates a cluster chain
but only returns the first cluster. Extend fat_add_cluster()
to add multiple clusters in a single call and rename it to
fat_add_clusters() to reflect the new behavior.

Link: https://lore.kernel.org/20261012171106.146243-3-matheus.aalmeida@inf.ufrgs.br
Signed-off-by: Matheus Alves de Almeida <matheus.aalmeida@inf.ufrgs.br>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

4 files changed, 23 insertions, 8 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index fbd207c55859..5784ca9061b6 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -395,6 +395,7 @@ extern int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 			 int new, int old, int wait);
 extern int fat_alloc_clusters(struct inode *inode, int *cluster,
 			      int nr_cluster);
+int fat_alloc_chain(struct inode *inode, int *cluster, int nr_cluster);
 extern int fat_free_clusters(struct inode *inode, int cluster);
 extern int fat_count_free_clusters(struct super_block *sb);
 extern int fat_trim_fs(struct inode *inode, struct fstrim_range *range);
@@ -440,7 +441,7 @@ static inline unsigned long fat_dir_hash(int logstart)
 {
 	return hash_32(logstart, FAT_HASH_BITS);
 }
-extern int fat_add_cluster(struct inode *inode);
+extern int fat_add_clusters(struct inode *inode, int nr_cluster);
 
 /* fat/misc.c */
 extern __printf(3, 4) __cold
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index e008fb4e72e0..2d10a815a579 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -503,7 +503,8 @@ static int fat_flush_bhs(struct super_block *sb, struct buffer_head **bhs,
 	return 0;
 }
 
-int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
+static int __fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster,
+				bool return_all)
 {
 	struct super_block *sb = inode->i_sb;
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
@@ -546,7 +547,10 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 				if (sbi->free_clusters != -1)
 					sbi->free_clusters--;
 
-				cluster[idx_clus] = entry;
+				if (return_all)
+					cluster[idx_clus] = entry;
+				else if (!idx_clus)
+					*cluster = entry;
 				idx_clus++;
 
 				if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
@@ -596,6 +600,16 @@ out:
 	return err;
 }
 
+int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
+{
+	return __fat_alloc_clusters(inode, cluster, nr_cluster, true);
+}
+
+int fat_alloc_chain(struct inode *inode, int *cluster, int nr_cluster)
+{
+	return __fat_alloc_clusters(inode, cluster, nr_cluster, false);
+}
+
 int fat_free_clusters(struct inode *inode, int cluster)
 {
 	struct super_block *sb = inode->i_sb;
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 6c475c53334c..fc77d20e8fe7 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -292,7 +292,7 @@ static long fat_fallocate(struct file *file, int mode,
 
 		/* Start the allocation.We are not zeroing out the clusters */
 		while (nr_cluster-- > 0) {
-			err = fat_add_cluster(inode);
+			err = fat_add_clusters(inode, 1);
 			if (err)
 				goto error;
 		}
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 0b0bbe777842..d85c8fbdcca4 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -102,16 +102,16 @@ static struct fat_floppy_defaults {
 },
 };
 
-int fat_add_cluster(struct inode *inode)
+int fat_add_clusters(struct inode *inode, int nr_cluster)
 {
 	int err, cluster;
 
-	err = fat_alloc_clusters(inode, &cluster, 1);
+	err = fat_alloc_chain(inode, &cluster, nr_cluster);
 	if (err)
 		return err;
 	/* FIXME: this cluster should be added after data of this
 	 * cluster is writed */
-	err = fat_chain_add(inode, cluster, 1);
+	err = fat_chain_add(inode, cluster, nr_cluster);
 	if (err)
 		fat_free_clusters(inode, cluster);
 	return err;
@@ -153,7 +153,7 @@ static inline int __fat_get_block(struct inode *inode, sector_t iblock,
 	 */
 	if (!offset && !(iblock < last_block)) {
 		/* TODO: multiple cluster allocation would be desirable. */
-		err = fat_add_cluster(inode);
+		err = fat_add_clusters(inode, 1);
 		if (err)
 			return err;
 	}