4 files changed, 294 insertions, 51 deletions

diff --git a/fs/zonefs/Makefile b/fs/zonefs/Makefile
index 33c1a4f1132e..9fe54f5319f2 100644
--- a/fs/zonefs/Makefile
+++ b/fs/zonefs/Makefile
@@ -3,4 +3,4 @@ ccflags-y				+= -I$(src)
 
 obj-$(CONFIG_ZONEFS_FS) += zonefs.o
 
-zonefs-y	:= super.o
+zonefs-y	:= super.o sysfs.o
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 82da583da17b..b3b0b71fdf6c 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -27,6 +27,39 @@
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
+/*
+ * Manage the active zone count. Called with zi->i_truncate_mutex held.
+ */
+static void zonefs_account_active(struct inode *inode)
+{
+	struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+	struct zonefs_inode_info *zi = ZONEFS_I(inode);
+
+	lockdep_assert_held(&zi->i_truncate_mutex);
+
+	if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
+		return;
+
+	/*
+	 * If the zone is active, that is, if it is explicitly open or
+	 * partially written, check if it was already accounted as active.
+	 */
+	if ((zi->i_flags & ZONEFS_ZONE_OPEN) ||
+	    (zi->i_wpoffset > 0 && zi->i_wpoffset < zi->i_max_size)) {
+		if (!(zi->i_flags & ZONEFS_ZONE_ACTIVE)) {
+			zi->i_flags |= ZONEFS_ZONE_ACTIVE;
+			atomic_inc(&sbi->s_active_seq_files);
+		}
+		return;
+	}
+
+	/* The zone is not active. If it was, update the active count */
+	if (zi->i_flags & ZONEFS_ZONE_ACTIVE) {
+		zi->i_flags &= ~ZONEFS_ZONE_ACTIVE;
+		atomic_dec(&sbi->s_active_seq_files);
+	}
+}
+
 static inline int zonefs_zone_mgmt(struct inode *inode,
 				   enum req_opf op)
 {
@@ -68,8 +101,13 @@ static inline void zonefs_i_size_write(struct inode *inode, loff_t isize)
 	 * A full zone is no longer open/active and does not need
 	 * explicit closing.
 	 */
-	if (isize >= zi->i_max_size)
-		zi->i_flags &= ~ZONEFS_ZONE_OPEN;
+	if (isize >= zi->i_max_size) {
+		struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+
+		if (zi->i_flags & ZONEFS_ZONE_ACTIVE)
+			atomic_dec(&sbi->s_active_seq_files);
+		zi->i_flags &= ~(ZONEFS_ZONE_OPEN | ZONEFS_ZONE_ACTIVE);
+	}
 }
 
 static int zonefs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
@@ -397,6 +435,7 @@ static int zonefs_io_error_cb(struct blk_zone *zone, unsigned int idx,
 	zonefs_update_stats(inode, data_size);
 	zonefs_i_size_write(inode, data_size);
 	zi->i_wpoffset = data_size;
+	zonefs_account_active(inode);
 
 	return 0;
 }
@@ -508,6 +547,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
 	zonefs_update_stats(inode, isize);
 	truncate_setsize(inode, isize);
 	zi->i_wpoffset = isize;
+	zonefs_account_active(inode);
 
 unlock:
 	mutex_unlock(&zi->i_truncate_mutex);
@@ -865,8 +905,15 @@ static ssize_t zonefs_file_dio_write(struct kiocb *iocb, struct iov_iter *from)
 	    (ret > 0 || ret == -EIOCBQUEUED)) {
 		if (ret > 0)
 			count = ret;
+
+		/*
+		 * Update the zone write pointer offset assuming the write
+		 * operation succeeded. If it did not, the error recovery path
+		 * will correct it. Also do active seq file accounting.
+		 */
 		mutex_lock(&zi->i_truncate_mutex);
 		zi->i_wpoffset += count;
+		zonefs_account_active(inode);
 		mutex_unlock(&zi->i_truncate_mutex);
 	}
 
@@ -1008,13 +1055,13 @@ inode_unlock:
 	return ret;
 }
 
-static inline bool zonefs_file_use_exp_open(struct inode *inode, struct file *file)
+/*
+ * Write open accounting is done only for sequential files.
+ */
+static inline bool zonefs_seq_file_need_wro(struct inode *inode,
+					    struct file *file)
 {
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
-	struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
-
-	if (!(sbi->s_mount_opts & ZONEFS_MNTOPT_EXPLICIT_OPEN))
-		return false;
 
 	if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
 		return false;
@@ -1025,28 +1072,34 @@ static inline bool zonefs_file_use_exp_open(struct inode *inode, struct file *fi
 	return true;
 }
 
-static int zonefs_open_zone(struct inode *inode)
+static int zonefs_seq_file_write_open(struct inode *inode)
 {
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
-	struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
 	int ret = 0;
 
 	mutex_lock(&zi->i_truncate_mutex);
 
 	if (!zi->i_wr_refcnt) {
-		if (atomic_inc_return(&sbi->s_open_zones) > sbi->s_max_open_zones) {
-			atomic_dec(&sbi->s_open_zones);
-			ret = -EBUSY;
-			goto unlock;
-		}
+		struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
+		unsigned int wro = atomic_inc_return(&sbi->s_wro_seq_files);
 
-		if (i_size_read(inode) < zi->i_max_size) {
-			ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_OPEN);
-			if (ret) {
-				atomic_dec(&sbi->s_open_zones);
+		if (sbi->s_mount_opts & ZONEFS_MNTOPT_EXPLICIT_OPEN) {
+
+			if (wro > sbi->s_max_wro_seq_files) {
+				atomic_dec(&sbi->s_wro_seq_files);
+				ret = -EBUSY;
 				goto unlock;
 			}
-			zi->i_flags |= ZONEFS_ZONE_OPEN;
+
+			if (i_size_read(inode) < zi->i_max_size) {
+				ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_OPEN);
+				if (ret) {
+					atomic_dec(&sbi->s_wro_seq_files);
+					goto unlock;
+				}
+				zi->i_flags |= ZONEFS_ZONE_OPEN;
+				zonefs_account_active(inode);
+			}
 		}
 	}
 
@@ -1066,30 +1119,31 @@ static int zonefs_file_open(struct inode *inode, struct file *file)
 	if (ret)
 		return ret;
 
-	if (zonefs_file_use_exp_open(inode, file))
-		return zonefs_open_zone(inode);
+	if (zonefs_seq_file_need_wro(inode, file))
+		return zonefs_seq_file_write_open(inode);
 
 	return 0;
 }
 
-static void zonefs_close_zone(struct inode *inode)
+static void zonefs_seq_file_write_close(struct inode *inode)
 {
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
+	struct super_block *sb = inode->i_sb;
+	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
 	int ret = 0;
 
 	mutex_lock(&zi->i_truncate_mutex);
-	zi->i_wr_refcnt--;
-	if (!zi->i_wr_refcnt) {
-		struct zonefs_sb_info *sbi = ZONEFS_SB(inode->i_sb);
-		struct super_block *sb = inode->i_sb;
 
-		/*
-		 * If the file zone is full, it is not open anymore and we only
-		 * need to decrement the open count.
-		 */
-		if (!(zi->i_flags & ZONEFS_ZONE_OPEN))
-			goto dec;
+	zi->i_wr_refcnt--;
+	if (zi->i_wr_refcnt)
+		goto unlock;
 
+	/*
+	 * The file zone may not be open anymore (e.g. the file was truncated to
+	 * its maximum size or it was fully written). For this case, we only
+	 * need to decrement the write open count.
+	 */
+	if (zi->i_flags & ZONEFS_ZONE_OPEN) {
 		ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_CLOSE);
 		if (ret) {
 			__zonefs_io_error(inode, false);
@@ -1101,14 +1155,23 @@ static void zonefs_close_zone(struct inode *inode)
 			 */
 			if (zi->i_flags & ZONEFS_ZONE_OPEN &&
 			    !(sb->s_flags & SB_RDONLY)) {
-				zonefs_warn(sb, "closing zone failed, remounting filesystem read-only\n");
+				zonefs_warn(sb,
+					"closing zone at %llu failed %d\n",
+					zi->i_zsector, ret);
+				zonefs_warn(sb,
+					"remounting filesystem read-only\n");
 				sb->s_flags |= SB_RDONLY;
 			}
+			goto unlock;
 		}
+
 		zi->i_flags &= ~ZONEFS_ZONE_OPEN;
-dec:
-		atomic_dec(&sbi->s_open_zones);
+		zonefs_account_active(inode);
 	}
+
+	atomic_dec(&sbi->s_wro_seq_files);
+
+unlock:
 	mutex_unlock(&zi->i_truncate_mutex);
 }
 
@@ -1120,8 +1183,8 @@ static int zonefs_file_release(struct inode *inode, struct file *file)
 	 * the zone has gone offline or read-only). Make sure we don't fail the
 	 * close(2) for user-space.
 	 */
-	if (zonefs_file_use_exp_open(inode, file))
-		zonefs_close_zone(inode);
+	if (zonefs_seq_file_need_wro(inode, file))
+		zonefs_seq_file_write_close(inode);
 
 	return 0;
 }
@@ -1310,7 +1373,7 @@ static int zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
 	struct super_block *sb = inode->i_sb;
 	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
-	int ret = 0;
+	int ret;
 
 	inode->i_ino = zone->start >> sbi->s_zone_sectors_shift;
 	inode->i_mode = S_IFREG | sbi->s_perm;
@@ -1336,6 +1399,8 @@ static int zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
 	sbi->s_blocks += zi->i_max_size >> sb->s_blocksize_bits;
 	sbi->s_used_blocks += zi->i_wpoffset >> sb->s_blocksize_bits;
 
+	mutex_lock(&zi->i_truncate_mutex);
+
 	/*
 	 * For sequential zones, make sure that any open zone is closed first
 	 * to ensure that the initial number of open zones is 0, in sync with
@@ -1345,12 +1410,17 @@ static int zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
 	if (type == ZONEFS_ZTYPE_SEQ &&
 	    (zone->cond == BLK_ZONE_COND_IMP_OPEN ||
 	     zone->cond == BLK_ZONE_COND_EXP_OPEN)) {
-		mutex_lock(&zi->i_truncate_mutex);
 		ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_CLOSE);
-		mutex_unlock(&zi->i_truncate_mutex);
+		if (ret)
+			goto unlock;
 	}
 
-	return ret;
+	zonefs_account_active(inode);
+
+unlock:
+	mutex_unlock(&zi->i_truncate_mutex);
+
+	return 0;
 }
 
 static struct dentry *zonefs_create_inode(struct dentry *parent,
@@ -1687,14 +1757,18 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_gid = GLOBAL_ROOT_GID;
 	sbi->s_perm = 0640;
 	sbi->s_mount_opts = ZONEFS_MNTOPT_ERRORS_RO;
-	sbi->s_max_open_zones = bdev_max_open_zones(sb->s_bdev);
-	atomic_set(&sbi->s_open_zones, 0);
-	if (!sbi->s_max_open_zones &&
+
+	atomic_set(&sbi->s_wro_seq_files, 0);
+	sbi->s_max_wro_seq_files = bdev_max_open_zones(sb->s_bdev);
+	if (!sbi->s_max_wro_seq_files &&
 	    sbi->s_mount_opts & ZONEFS_MNTOPT_EXPLICIT_OPEN) {
 		zonefs_info(sb, "No open zones limit. Ignoring explicit_open mount option\n");
 		sbi->s_mount_opts &= ~ZONEFS_MNTOPT_EXPLICIT_OPEN;
 	}
 
+	atomic_set(&sbi->s_active_seq_files, 0);
+	sbi->s_max_active_seq_files = bdev_max_active_zones(sb->s_bdev);
+
 	ret = zonefs_read_super(sb);
 	if (ret)
 		return ret;
@@ -1709,6 +1783,10 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
 	if (ret)
 		goto cleanup;
 
+	ret = zonefs_sysfs_register(sb);
+	if (ret)
+		goto cleanup;
+
 	zonefs_info(sb, "Mounting %u zones",
 		    blkdev_nr_zones(sb->s_bdev->bd_disk));
 
@@ -1754,6 +1832,8 @@ static void zonefs_kill_super(struct super_block *sb)
 
 	if (sb->s_root)
 		d_genocide(sb->s_root);
+
+	zonefs_sysfs_unregister(sb);
 	kill_block_super(sb);
 	kfree(sbi);
 }
@@ -1801,16 +1881,26 @@ static int __init zonefs_init(void)
 		return ret;
 
 	ret = register_filesystem(&zonefs_type);
-	if (ret) {
-		zonefs_destroy_inodecache();
-		return ret;
-	}
+	if (ret)
+		goto destroy_inodecache;
+
+	ret = zonefs_sysfs_init();
+	if (ret)
+		goto unregister_fs;
 
 	return 0;
+
+unregister_fs:
+	unregister_filesystem(&zonefs_type);
+destroy_inodecache:
+	zonefs_destroy_inodecache();
+
+	return ret;
 }
 
 static void __exit zonefs_exit(void)
 {
+	zonefs_sysfs_exit();
 	zonefs_destroy_inodecache();
 	unregister_filesystem(&zonefs_type);
 }
diff --git a/fs/zonefs/sysfs.c b/fs/zonefs/sysfs.c
new file mode 100644
index 000000000000..9cb6755ce39a
--- /dev/null
+++ b/fs/zonefs/sysfs.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple file system for zoned block devices exposing zones as files.
+ *
+ * Copyright (C) 2022 Western Digital Corporation or its affiliates.
+ */
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/blkdev.h>
+
+#include "zonefs.h"
+
+struct zonefs_sysfs_attr {
+	struct attribute attr;
+	ssize_t (*show)(struct zonefs_sb_info *sbi, char *buf);
+};
+
+static inline struct zonefs_sysfs_attr *to_attr(struct attribute *attr)
+{
+	return container_of(attr, struct zonefs_sysfs_attr, attr);
+}
+
+#define ZONEFS_SYSFS_ATTR_RO(name) \
+static struct zonefs_sysfs_attr zonefs_sysfs_attr_##name = __ATTR_RO(name)
+
+#define ATTR_LIST(name) &zonefs_sysfs_attr_##name.attr
+
+static ssize_t zonefs_sysfs_attr_show(struct kobject *kobj,
+				      struct attribute *attr, char *buf)
+{
+	struct zonefs_sb_info *sbi =
+		container_of(kobj, struct zonefs_sb_info, s_kobj);
+	struct zonefs_sysfs_attr *zonefs_attr =
+		container_of(attr, struct zonefs_sysfs_attr, attr);
+
+	if (!zonefs_attr->show)
+		return 0;
+
+	return zonefs_attr->show(sbi, buf);
+}
+
+static ssize_t max_wro_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%u\n", sbi->s_max_wro_seq_files);
+}
+ZONEFS_SYSFS_ATTR_RO(max_wro_seq_files);
+
+static ssize_t nr_wro_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", atomic_read(&sbi->s_wro_seq_files));
+}
+ZONEFS_SYSFS_ATTR_RO(nr_wro_seq_files);
+
+static ssize_t max_active_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%u\n", sbi->s_max_active_seq_files);
+}
+ZONEFS_SYSFS_ATTR_RO(max_active_seq_files);
+
+static ssize_t nr_active_seq_files_show(struct zonefs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", atomic_read(&sbi->s_active_seq_files));
+}
+ZONEFS_SYSFS_ATTR_RO(nr_active_seq_files);
+
+static struct attribute *zonefs_sysfs_attrs[] = {
+	ATTR_LIST(max_wro_seq_files),
+	ATTR_LIST(nr_wro_seq_files),
+	ATTR_LIST(max_active_seq_files),
+	ATTR_LIST(nr_active_seq_files),
+	NULL,
+};
+ATTRIBUTE_GROUPS(zonefs_sysfs);
+
+static void zonefs_sysfs_sb_release(struct kobject *kobj)
+{
+	struct zonefs_sb_info *sbi =
+		container_of(kobj, struct zonefs_sb_info, s_kobj);
+
+	complete(&sbi->s_kobj_unregister);
+}
+
+static const struct sysfs_ops zonefs_sysfs_attr_ops = {
+	.show	= zonefs_sysfs_attr_show,
+};
+
+static struct kobj_type zonefs_sb_ktype = {
+	.default_groups = zonefs_sysfs_groups,
+	.sysfs_ops	= &zonefs_sysfs_attr_ops,
+	.release	= zonefs_sysfs_sb_release,
+};
+
+static struct kobject *zonefs_sysfs_root;
+
+int zonefs_sysfs_register(struct super_block *sb)
+{
+	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+	int ret;
+
+	init_completion(&sbi->s_kobj_unregister);
+	ret = kobject_init_and_add(&sbi->s_kobj, &zonefs_sb_ktype,
+				   zonefs_sysfs_root, "%s", sb->s_id);
+	if (ret) {
+		kobject_put(&sbi->s_kobj);
+		wait_for_completion(&sbi->s_kobj_unregister);
+		return ret;
+	}
+
+	sbi->s_sysfs_registered = true;
+
+	return 0;
+}
+
+void zonefs_sysfs_unregister(struct super_block *sb)
+{
+	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
+
+	if (!sbi || !sbi->s_sysfs_registered)
+		return;
+
+	kobject_del(&sbi->s_kobj);
+	kobject_put(&sbi->s_kobj);
+	wait_for_completion(&sbi->s_kobj_unregister);
+}
+
+int __init zonefs_sysfs_init(void)
+{
+	zonefs_sysfs_root = kobject_create_and_add("zonefs", fs_kobj);
+	if (!zonefs_sysfs_root)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void zonefs_sysfs_exit(void)
+{
+	kobject_put(zonefs_sysfs_root);
+	zonefs_sysfs_root = NULL;
+}
diff --git a/fs/zonefs/zonefs.h b/fs/zonefs/zonefs.h
index 7b147907c328..4b3de66c3233 100644
--- a/fs/zonefs/zonefs.h
+++ b/fs/zonefs/zonefs.h
@@ -12,6 +12,7 @@
 #include <linux/uuid.h>
 #include <linux/mutex.h>
 #include <linux/rwsem.h>
+#include <linux/kobject.h>
 
 /*
  * Maximum length of file names: this only needs to be large enough to fit
@@ -39,6 +40,7 @@ static inline enum zonefs_ztype zonefs_zone_type(struct blk_zone *zone)
 }
 
 #define ZONEFS_ZONE_OPEN	(1 << 0)
+#define ZONEFS_ZONE_ACTIVE	(1 << 1)
 
 /*
  * In-memory inode data.
@@ -182,8 +184,15 @@ struct zonefs_sb_info {
 	loff_t			s_blocks;
 	loff_t			s_used_blocks;
 
-	unsigned int		s_max_open_zones;
-	atomic_t		s_open_zones;
+	unsigned int		s_max_wro_seq_files;
+	atomic_t		s_wro_seq_files;
+
+	unsigned int		s_max_active_seq_files;
+	atomic_t		s_active_seq_files;
+
+	bool			s_sysfs_registered;
+	struct kobject		s_kobj;
+	struct completion	s_kobj_unregister;
 };
 
 static inline struct zonefs_sb_info *ZONEFS_SB(struct super_block *sb)
@@ -198,4 +207,9 @@ static inline struct zonefs_sb_info *ZONEFS_SB(struct super_block *sb)
 #define zonefs_warn(sb, format, args...)	\
 	pr_warn("zonefs (%s) WARNING: " format, sb->s_id, ## args)
 
+int zonefs_sysfs_register(struct super_block *sb);
+void zonefs_sysfs_unregister(struct super_block *sb);
+int zonefs_sysfs_init(void);
+void zonefs_sysfs_exit(void);
+
 #endif