[PATCH 4/4] zonefs: fix synchronous write to sequential zone files

[Damien Le Moal <damien.lemoal@wdc.com>]

Synchronous writes to sequential zone files cannot use zone append
operations if the underlying zoned device queue limit
max_zone_append_sectors is 0, indicating that the device does not
support this operation. In this case, fall back to using regular write
operations.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 fs/zonefs/super.c  | 16 ++++++++++++----
 fs/zonefs/zonefs.h |  2 ++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 049e36c69ed7..b97566b9dff7 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -689,14 +689,15 @@ static ssize_t zonefs_file_dio_append(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
-	struct block_device *bdev = inode->i_sb->s_bdev;
-	unsigned int max;
+	struct super_block *sb = inode->i_sb;
+	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+	struct block_device *bdev = sb->s_bdev;
+	sector_t max = sbi->s_max_zone_append_sectors;
 	struct bio *bio;
 	ssize_t size;
 	int nr_pages;
 	ssize_t ret;
 
-	max = queue_max_zone_append_sectors(bdev_get_queue(bdev));
 	max = ALIGN_DOWN(max << SECTOR_SHIFT, inode->i_sb->s_blocksize);
 	iov_iter_truncate(from, max);
 
@@ -853,6 +854,8 @@ static ssize_t zonefs_file_dio_write(struct kiocb *iocb, struct iov_iter *from)
 
 	/* Enforce sequential writes (append only) in sequential zones */
 	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ) {
+		struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+
 		mutex_lock(&zi->i_truncate_mutex);
 		if (iocb->ki_pos != zi->i_wpoffset) {
 			mutex_unlock(&zi->i_truncate_mutex);
@@ -860,7 +863,7 @@ static ssize_t zonefs_file_dio_write(struct kiocb *iocb, struct iov_iter *from)
 			goto inode_unlock;
 		}
 		mutex_unlock(&zi->i_truncate_mutex);
-		append = sync;
+		append = sync && sbi->s_max_zone_append_sectors;
 	}
 
 	if (append)
@@ -1683,6 +1686,11 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
 		sbi->s_mount_opts &= ~ZONEFS_MNTOPT_EXPLICIT_OPEN;
 	}
 
+	sbi->s_max_zone_append_sectors =
+		queue_max_zone_append_sectors(bdev_get_queue(sb->s_bdev));
+	if (!sbi->s_max_zone_append_sectors)
+		zonefs_info(sb, "Zone append is not supported: falling back to using regular writes\n");
+
 	ret = zonefs_read_super(sb);
 	if (ret)
 		return ret;
diff --git a/fs/zonefs/zonefs.h b/fs/zonefs/zonefs.h
index 51141907097c..2b8c3b1a32ea 100644
--- a/fs/zonefs/zonefs.h
+++ b/fs/zonefs/zonefs.h
@@ -185,6 +185,8 @@ struct zonefs_sb_info {
 
 	unsigned int		s_max_open_zones;
 	atomic_t		s_open_zones;
+
+	sector_t		s_max_zone_append_sectors;
 };
 
 static inline struct zonefs_sb_info *ZONEFS_SB(struct super_block *sb)
-- 
2.30.2