text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Simple file system for zoned block devices exposing zones as files.
   *
   * Copyright (C) 2019 Western Digital Corporation or its affiliates.
   */
  #include <linux/module.h>
  #include <linux/pagemap.h>
  #include <linux/magic.h>
  #include <linux/iomap.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/blkdev.h>
  #include <linux/statfs.h>
  #include <linux/writeback.h>
  #include <linux/quotaops.h>
  #include <linux/seq_file.h>
  #include <linux/parser.h>
  #include <linux/uio.h>
  #include <linux/mman.h>
  #include <linux/sched/mm.h>
  #include <linux/crc32.h>
  #include <linux/task_io_accounting_ops.h>
  
  #include "zonefs.h"
  
  #define CREATE_TRACE_POINTS
  #include "trace.h"
  
  static inline int zonefs_zone_mgmt(struct inode *inode,
  				   enum req_opf op)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	int ret;
  
  	lockdep_assert_held(&zi->i_truncate_mutex);
  
  	trace_zonefs_zone_mgmt(inode, op);
  	ret = blkdev_zone_mgmt(inode->i_sb->s_bdev, op, zi->i_zsector,
  			       zi->i_zone_size >> SECTOR_SHIFT, GFP_NOFS);
  	if (ret) {
  		zonefs_err(inode->i_sb,
  			   "Zone management operation %s at %llu failed %d\n",
  			   blk_op_str(op), zi->i_zsector, ret);
  		return ret;
  	}
  
  	return 0;
  }
  
  static inline void zonefs_i_size_write(struct inode *inode, loff_t isize)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	i_size_write(inode, 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;
  }
  
  static int zonefs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
  			      unsigned int flags, struct iomap *iomap,
  			      struct iomap *srcmap)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	struct super_block *sb = inode->i_sb;
  	loff_t isize;
  
  	/* All I/Os should always be within the file maximum size */
  	if (WARN_ON_ONCE(offset + length > zi->i_max_size))
  		return -EIO;
  
  	/*
  	 * Sequential zones can only accept direct writes. This is already
  	 * checked when writes are issued, so warn if we see a page writeback
  	 * operation.
  	 */
  	if (WARN_ON_ONCE(zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
  			 (flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT)))
  		return -EIO;
  
  	/*
  	 * For conventional zones, all blocks are always mapped. For sequential
  	 * zones, all blocks after always mapped below the inode size (zone
  	 * write pointer) and unwriten beyond.
  	 */
  	mutex_lock(&zi->i_truncate_mutex);
  	isize = i_size_read(inode);
  	if (offset >= isize)
  		iomap->type = IOMAP_UNWRITTEN;
  	else
  		iomap->type = IOMAP_MAPPED;
  	if (flags & IOMAP_WRITE)
  		length = zi->i_max_size - offset;
  	else
  		length = min(length, isize - offset);
  	mutex_unlock(&zi->i_truncate_mutex);
  
  	iomap->offset = ALIGN_DOWN(offset, sb->s_blocksize);
  	iomap->length = ALIGN(offset + length, sb->s_blocksize) - iomap->offset;
  	iomap->bdev = inode->i_sb->s_bdev;
  	iomap->addr = (zi->i_zsector << SECTOR_SHIFT) + iomap->offset;
  
  	trace_zonefs_iomap_begin(inode, iomap);
  
  	return 0;
  }
  
  static const struct iomap_ops zonefs_iomap_ops = {
  	.iomap_begin	= zonefs_iomap_begin,
  };
  
  static int zonefs_readpage(struct file *unused, struct page *page)
  {
  	return iomap_readpage(page, &zonefs_iomap_ops);
  }
  
  static void zonefs_readahead(struct readahead_control *rac)
  {
  	iomap_readahead(rac, &zonefs_iomap_ops);
  }
  
  /*
   * Map blocks for page writeback. This is used only on conventional zone files,
   * which implies that the page range can only be within the fixed inode size.
   */
  static int zonefs_map_blocks(struct iomap_writepage_ctx *wpc,
  			     struct inode *inode, loff_t offset)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	if (WARN_ON_ONCE(zi->i_ztype != ZONEFS_ZTYPE_CNV))
  		return -EIO;
  	if (WARN_ON_ONCE(offset >= i_size_read(inode)))
  		return -EIO;
  
  	/* If the mapping is already OK, nothing needs to be done */
  	if (offset >= wpc->iomap.offset &&
  	    offset < wpc->iomap.offset + wpc->iomap.length)
  		return 0;
  
  	return zonefs_iomap_begin(inode, offset, zi->i_max_size - offset,
  				  IOMAP_WRITE, &wpc->iomap, NULL);
  }
  
  static const struct iomap_writeback_ops zonefs_writeback_ops = {
  	.map_blocks		= zonefs_map_blocks,
  };
  
  static int zonefs_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct iomap_writepage_ctx wpc = { };
  
  	return iomap_writepage(page, wbc, &wpc, &zonefs_writeback_ops);
  }
  
  static int zonefs_writepages(struct address_space *mapping,
  			     struct writeback_control *wbc)
  {
  	struct iomap_writepage_ctx wpc = { };
  
  	return iomap_writepages(mapping, wbc, &wpc, &zonefs_writeback_ops);
  }
  
  static int zonefs_swap_activate(struct swap_info_struct *sis,
  				struct file *swap_file, sector_t *span)
  {
  	struct inode *inode = file_inode(swap_file);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	if (zi->i_ztype != ZONEFS_ZTYPE_CNV) {
  		zonefs_err(inode->i_sb,
  			   "swap file: not a conventional zone file\n");
  		return -EINVAL;
  	}
  
  	return iomap_swapfile_activate(sis, swap_file, span, &zonefs_iomap_ops);
  }
  
  static const struct address_space_operations zonefs_file_aops = {
  	.readpage		= zonefs_readpage,
  	.readahead		= zonefs_readahead,
  	.writepage		= zonefs_writepage,
  	.writepages		= zonefs_writepages,
  	.set_page_dirty		= __set_page_dirty_nobuffers,
  	.releasepage		= iomap_releasepage,
  	.invalidatepage		= iomap_invalidatepage,
  	.migratepage		= iomap_migrate_page,
  	.is_partially_uptodate	= iomap_is_partially_uptodate,
  	.error_remove_page	= generic_error_remove_page,
  	.direct_IO		= noop_direct_IO,
  	.swap_activate		= zonefs_swap_activate,
  };
  
  static void zonefs_update_stats(struct inode *inode, loff_t new_isize)
  {
  	struct super_block *sb = inode->i_sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	loff_t old_isize = i_size_read(inode);
  	loff_t nr_blocks;
  
  	if (new_isize == old_isize)
  		return;
  
  	spin_lock(&sbi->s_lock);
  
  	/*
  	 * This may be called for an update after an IO error.
  	 * So beware of the values seen.
  	 */
  	if (new_isize < old_isize) {
  		nr_blocks = (old_isize - new_isize) >> sb->s_blocksize_bits;
  		if (sbi->s_used_blocks > nr_blocks)
  			sbi->s_used_blocks -= nr_blocks;
  		else
  			sbi->s_used_blocks = 0;
  	} else {
  		sbi->s_used_blocks +=
  			(new_isize - old_isize) >> sb->s_blocksize_bits;
  		if (sbi->s_used_blocks > sbi->s_blocks)
  			sbi->s_used_blocks = sbi->s_blocks;
  	}
  
  	spin_unlock(&sbi->s_lock);
  }
  
  /*
   * Check a zone condition and adjust its file inode access permissions for
   * offline and readonly zones. Return the inode size corresponding to the
   * amount of readable data in the zone.
   */
  static loff_t zonefs_check_zone_condition(struct inode *inode,
  					  struct blk_zone *zone, bool warn,
  					  bool mount)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	switch (zone->cond) {
  	case BLK_ZONE_COND_OFFLINE:
  		/*
  		 * Dead zone: make the inode immutable, disable all accesses
  		 * and set the file size to 0 (zone wp set to zone start).
  		 */
  		if (warn)
  			zonefs_warn(inode->i_sb, "inode %lu: offline zone\n",
  				    inode->i_ino);
  		inode->i_flags |= S_IMMUTABLE;
  		inode->i_mode &= ~0777;
  		zone->wp = zone->start;
  		return 0;
  	case BLK_ZONE_COND_READONLY:
  		/*
  		 * The write pointer of read-only zones is invalid. If such a
  		 * zone is found during mount, the file size cannot be retrieved
  		 * so we treat the zone as offline (mount == true case).
  		 * Otherwise, keep the file size as it was when last updated
  		 * so that the user can recover data. In both cases, writes are
  		 * always disabled for the zone.
  		 */
  		if (warn)
  			zonefs_warn(inode->i_sb, "inode %lu: read-only zone\n",
  				    inode->i_ino);
  		inode->i_flags |= S_IMMUTABLE;
  		if (mount) {
  			zone->cond = BLK_ZONE_COND_OFFLINE;
  			inode->i_mode &= ~0777;
  			zone->wp = zone->start;
  			return 0;
  		}
  		inode->i_mode &= ~0222;
  		return i_size_read(inode);
  	case BLK_ZONE_COND_FULL:
  		/* The write pointer of full zones is invalid. */
  		return zi->i_max_size;
  	default:
  		if (zi->i_ztype == ZONEFS_ZTYPE_CNV)
  			return zi->i_max_size;
  		return (zone->wp - zone->start) << SECTOR_SHIFT;
  	}
  }
  
  struct zonefs_ioerr_data {
  	struct inode	*inode;
  	bool		write;
  };
  
  static int zonefs_io_error_cb(struct blk_zone *zone, unsigned int idx,
  			      void *data)
  {
  	struct zonefs_ioerr_data *err = data;
  	struct inode *inode = err->inode;
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	struct super_block *sb = inode->i_sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	loff_t isize, data_size;
  
  	/*
  	 * Check the zone condition: if the zone is not "bad" (offline or
  	 * read-only), read errors are simply signaled to the IO issuer as long
  	 * as there is no inconsistency between the inode size and the amount of
  	 * data writen in the zone (data_size).
  	 */
  	data_size = zonefs_check_zone_condition(inode, zone, true, false);
  	isize = i_size_read(inode);
  	if (zone->cond != BLK_ZONE_COND_OFFLINE &&
  	    zone->cond != BLK_ZONE_COND_READONLY &&
  	    !err->write && isize == data_size)
  		return 0;
  
  	/*
  	 * At this point, we detected either a bad zone or an inconsistency
  	 * between the inode size and the amount of data written in the zone.
  	 * For the latter case, the cause may be a write IO error or an external
  	 * action on the device. Two error patterns exist:
  	 * 1) The inode size is lower than the amount of data in the zone:
  	 *    a write operation partially failed and data was writen at the end
  	 *    of the file. This can happen in the case of a large direct IO
  	 *    needing several BIOs and/or write requests to be processed.
  	 * 2) The inode size is larger than the amount of data in the zone:
  	 *    this can happen with a deferred write error with the use of the
  	 *    device side write cache after getting successful write IO
  	 *    completions. Other possibilities are (a) an external corruption,
  	 *    e.g. an application reset the zone directly, or (b) the device
  	 *    has a serious problem (e.g. firmware bug).
  	 *
  	 * In all cases, warn about inode size inconsistency and handle the
  	 * IO error according to the zone condition and to the mount options.
  	 */
  	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ && isize != data_size)
  		zonefs_warn(sb, "inode %lu: invalid size %lld (should be %lld)\n",
  			    inode->i_ino, isize, data_size);
  
  	/*
  	 * First handle bad zones signaled by hardware. The mount options
  	 * errors=zone-ro and errors=zone-offline result in changing the
  	 * zone condition to read-only and offline respectively, as if the
  	 * condition was signaled by the hardware.
  	 */
  	if (zone->cond == BLK_ZONE_COND_OFFLINE ||
  	    sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZOL) {
  		zonefs_warn(sb, "inode %lu: read/write access disabled\n",
  			    inode->i_ino);
  		if (zone->cond != BLK_ZONE_COND_OFFLINE) {
  			zone->cond = BLK_ZONE_COND_OFFLINE;
  			data_size = zonefs_check_zone_condition(inode, zone,
  								false, false);
  		}
  	} else if (zone->cond == BLK_ZONE_COND_READONLY ||
  		   sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZRO) {
  		zonefs_warn(sb, "inode %lu: write access disabled\n",
  			    inode->i_ino);
  		if (zone->cond != BLK_ZONE_COND_READONLY) {
  			zone->cond = BLK_ZONE_COND_READONLY;
  			data_size = zonefs_check_zone_condition(inode, zone,
  								false, false);
  		}
  	}
  
  	/*
  	 * If the filesystem is mounted with the explicit-open mount option, we
  	 * need to clear the ZONEFS_ZONE_OPEN flag if the zone transitioned to
  	 * the read-only or offline condition, to avoid attempting an explicit
  	 * close of the zone when the inode file is closed.
  	 */
  	if ((sbi->s_mount_opts & ZONEFS_MNTOPT_EXPLICIT_OPEN) &&
  	    (zone->cond == BLK_ZONE_COND_OFFLINE ||
  	     zone->cond == BLK_ZONE_COND_READONLY))
  		zi->i_flags &= ~ZONEFS_ZONE_OPEN;
  
  	/*
  	 * If error=remount-ro was specified, any error result in remounting
  	 * the volume as read-only.
  	 */
  	if ((sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_RO) && !sb_rdonly(sb)) {
  		zonefs_warn(sb, "remounting filesystem read-only\n");
  		sb->s_flags |= SB_RDONLY;
  	}
  
  	/*
  	 * Update block usage stats and the inode size  to prevent access to
  	 * invalid data.
  	 */
  	zonefs_update_stats(inode, data_size);
  	zonefs_i_size_write(inode, data_size);
  	zi->i_wpoffset = data_size;
  
  	return 0;
  }
  
  /*
   * When an file IO error occurs, check the file zone to see if there is a change
   * in the zone condition (e.g. offline or read-only). For a failed write to a
   * sequential zone, the zone write pointer position must also be checked to
   * eventually correct the file size and zonefs inode write pointer offset
   * (which can be out of sync with the drive due to partial write failures).
   */
  static void __zonefs_io_error(struct inode *inode, bool write)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	struct super_block *sb = inode->i_sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	unsigned int noio_flag;
  	unsigned int nr_zones =
  		zi->i_zone_size >> (sbi->s_zone_sectors_shift + SECTOR_SHIFT);
  	struct zonefs_ioerr_data err = {
  		.inode = inode,
  		.write = write,
  	};
  	int ret;
  
  	/*
  	 * Memory allocations in blkdev_report_zones() can trigger a memory
  	 * reclaim which may in turn cause a recursion into zonefs as well as
  	 * struct request allocations for the same device. The former case may
  	 * end up in a deadlock on the inode truncate mutex, while the latter
  	 * may prevent IO forward progress. Executing the report zones under
  	 * the GFP_NOIO context avoids both problems.
  	 */
  	noio_flag = memalloc_noio_save();
  	ret = blkdev_report_zones(sb->s_bdev, zi->i_zsector, nr_zones,
  				  zonefs_io_error_cb, &err);
  	if (ret != nr_zones)
  		zonefs_err(sb, "Get inode %lu zone information failed %d\n",
  			   inode->i_ino, ret);
  	memalloc_noio_restore(noio_flag);
  }
  
  static void zonefs_io_error(struct inode *inode, bool write)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	mutex_lock(&zi->i_truncate_mutex);
  	__zonefs_io_error(inode, write);
  	mutex_unlock(&zi->i_truncate_mutex);
  }
  
  static int zonefs_file_truncate(struct inode *inode, loff_t isize)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	loff_t old_isize;
  	enum req_opf op;
  	int ret = 0;
  
  	/*
  	 * Only sequential zone files can be truncated and truncation is allowed
  	 * only down to a 0 size, which is equivalent to a zone reset, and to
  	 * the maximum file size, which is equivalent to a zone finish.
  	 */
  	if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
  		return -EPERM;
  
  	if (!isize)
  		op = REQ_OP_ZONE_RESET;
  	else if (isize == zi->i_max_size)
  		op = REQ_OP_ZONE_FINISH;
  	else
  		return -EPERM;
  
  	inode_dio_wait(inode);
  
  	/* Serialize against page faults */
  	filemap_invalidate_lock(inode->i_mapping);
  
  	/* Serialize against zonefs_iomap_begin() */
  	mutex_lock(&zi->i_truncate_mutex);
  
  	old_isize = i_size_read(inode);
  	if (isize == old_isize)
  		goto unlock;
  
  	ret = zonefs_zone_mgmt(inode, op);
  	if (ret)
  		goto unlock;
  
  	/*
  	 * If the mount option ZONEFS_MNTOPT_EXPLICIT_OPEN is set,
  	 * take care of open zones.
  	 */
  	if (zi->i_flags & ZONEFS_ZONE_OPEN) {
  		/*
  		 * Truncating a zone to EMPTY or FULL is the equivalent of
  		 * closing the zone. For a truncation to 0, we need to
  		 * re-open the zone to ensure new writes can be processed.
  		 * For a truncation to the maximum file size, the zone is
  		 * closed and writes cannot be accepted anymore, so clear
  		 * the open flag.
  		 */
  		if (!isize)
  			ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_OPEN);
  		else
  			zi->i_flags &= ~ZONEFS_ZONE_OPEN;
  	}
  
  	zonefs_update_stats(inode, isize);
  	truncate_setsize(inode, isize);
  	zi->i_wpoffset = isize;
  
  unlock:
  	mutex_unlock(&zi->i_truncate_mutex);
  	filemap_invalidate_unlock(inode->i_mapping);
  
  	return ret;
  }
  
  static int zonefs_inode_setattr(struct user_namespace *mnt_userns,
  				struct dentry *dentry, struct iattr *iattr)
  {
  	struct inode *inode = d_inode(dentry);
  	int ret;
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return -EPERM;
  
  	ret = setattr_prepare(&init_user_ns, dentry, iattr);
  	if (ret)
  		return ret;
  
  	/*
  	 * Since files and directories cannot be created nor deleted, do not
  	 * allow setting any write attributes on the sub-directories grouping
  	 * files by zone type.
  	 */
  	if ((iattr->ia_valid & ATTR_MODE) && S_ISDIR(inode->i_mode) &&
  	    (iattr->ia_mode & 0222))
  		return -EPERM;
  
  	if (((iattr->ia_valid & ATTR_UID) &&
  	     !uid_eq(iattr->ia_uid, inode->i_uid)) ||
  	    ((iattr->ia_valid & ATTR_GID) &&
  	     !gid_eq(iattr->ia_gid, inode->i_gid))) {
  		ret = dquot_transfer(inode, iattr);
  		if (ret)
  			return ret;
  	}
  
  	if (iattr->ia_valid & ATTR_SIZE) {
  		ret = zonefs_file_truncate(inode, iattr->ia_size);
  		if (ret)
  			return ret;
  	}
  
  	setattr_copy(&init_user_ns, inode, iattr);
  
  	return 0;
  }
  
  static const struct inode_operations zonefs_file_inode_operations = {
  	.setattr	= zonefs_inode_setattr,
  };
  
  static int zonefs_file_fsync(struct file *file, loff_t start, loff_t end,
  			     int datasync)
  {
  	struct inode *inode = file_inode(file);
  	int ret = 0;
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return -EPERM;
  
  	/*
  	 * Since only direct writes are allowed in sequential files, page cache
  	 * flush is needed only for conventional zone files.
  	 */
  	if (ZONEFS_I(inode)->i_ztype == ZONEFS_ZTYPE_CNV)
  		ret = file_write_and_wait_range(file, start, end);
  	if (!ret)
  		ret = blkdev_issue_flush(inode->i_sb->s_bdev);
  
  	if (ret)
  		zonefs_io_error(inode, true);
  
  	return ret;
  }
  
  static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
  {
  	struct inode *inode = file_inode(vmf->vma->vm_file);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	vm_fault_t ret;
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return VM_FAULT_SIGBUS;
  
  	/*
  	 * Sanity check: only conventional zone files can have shared
  	 * writeable mappings.
  	 */
  	if (WARN_ON_ONCE(zi->i_ztype != ZONEFS_ZTYPE_CNV))
  		return VM_FAULT_NOPAGE;
  
  	sb_start_pagefault(inode->i_sb);
  	file_update_time(vmf->vma->vm_file);
  
  	/* Serialize against truncates */
  	filemap_invalidate_lock_shared(inode->i_mapping);
  	ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
  	filemap_invalidate_unlock_shared(inode->i_mapping);
  
  	sb_end_pagefault(inode->i_sb);
  	return ret;
  }
  
  static const struct vm_operations_struct zonefs_file_vm_ops = {
  	.fault		= filemap_fault,
  	.map_pages	= filemap_map_pages,
  	.page_mkwrite	= zonefs_filemap_page_mkwrite,
  };
  
  static int zonefs_file_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	/*
  	 * Conventional zones accept random writes, so their files can support
  	 * shared writable mappings. For sequential zone files, only read
  	 * mappings are possible since there are no guarantees for write
  	 * ordering between msync() and page cache writeback.
  	 */
  	if (ZONEFS_I(file_inode(file))->i_ztype == ZONEFS_ZTYPE_SEQ &&
  	    (vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
  		return -EINVAL;
  
  	file_accessed(file);
  	vma->vm_ops = &zonefs_file_vm_ops;
  
  	return 0;
  }
  
  static loff_t zonefs_file_llseek(struct file *file, loff_t offset, int whence)
  {
  	loff_t isize = i_size_read(file_inode(file));
  
  	/*
  	 * Seeks are limited to below the zone size for conventional zones
  	 * and below the zone write pointer for sequential zones. In both
  	 * cases, this limit is the inode size.
  	 */
  	return generic_file_llseek_size(file, offset, whence, isize, isize);
  }
  
  static int zonefs_file_write_dio_end_io(struct kiocb *iocb, ssize_t size,
  					int error, unsigned int flags)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	if (error) {
  		zonefs_io_error(inode, true);
  		return error;
  	}
  
  	if (size && zi->i_ztype != ZONEFS_ZTYPE_CNV) {
  		/*
  		 * Note that we may be seeing completions out of order,
  		 * but that is not a problem since a write completed
  		 * successfully necessarily means that all preceding writes
  		 * were also successful. So we can safely increase the inode
  		 * size to the write end location.
  		 */
  		mutex_lock(&zi->i_truncate_mutex);
  		if (i_size_read(inode) < iocb->ki_pos + size) {
  			zonefs_update_stats(inode, iocb->ki_pos + size);
  			zonefs_i_size_write(inode, iocb->ki_pos + size);
  		}
  		mutex_unlock(&zi->i_truncate_mutex);
  	}
  
  	return 0;
  }
  
  static const struct iomap_dio_ops zonefs_write_dio_ops = {
  	.end_io			= zonefs_file_write_dio_end_io,
  };
  
  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 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);
  
  	nr_pages = iov_iter_npages(from, BIO_MAX_VECS);
  	if (!nr_pages)
  		return 0;
  
  	bio = bio_alloc(GFP_NOFS, nr_pages);
  	bio_set_dev(bio, bdev);
  	bio->bi_iter.bi_sector = zi->i_zsector;
  	bio->bi_write_hint = iocb->ki_hint;
  	bio->bi_ioprio = iocb->ki_ioprio;
  	bio->bi_opf = REQ_OP_ZONE_APPEND | REQ_SYNC | REQ_IDLE;
  	if (iocb->ki_flags & IOCB_DSYNC)
  		bio->bi_opf |= REQ_FUA;
  
  	ret = bio_iov_iter_get_pages(bio, from);
  	if (unlikely(ret))
  		goto out_release;
  
  	size = bio->bi_iter.bi_size;
  	task_io_account_write(size);
  
  	if (iocb->ki_flags & IOCB_HIPRI)
  		bio_set_polled(bio, iocb);
  
  	ret = submit_bio_wait(bio);
  
  	zonefs_file_write_dio_end_io(iocb, size, ret, 0);
  	trace_zonefs_file_dio_append(inode, size, ret);
  
  out_release:
  	bio_release_pages(bio, false);
  	bio_put(bio);
  
  	if (ret >= 0) {
  		iocb->ki_pos += size;
  		return size;
  	}
  
  	return ret;
  }
  
  /*
   * Do not exceed the LFS limits nor the file zone size. If pos is under the
   * limit it becomes a short access. If it exceeds the limit, return -EFBIG.
   */
  static loff_t zonefs_write_check_limits(struct file *file, loff_t pos,
  					loff_t count)
  {
  	struct inode *inode = file_inode(file);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	loff_t limit = rlimit(RLIMIT_FSIZE);
  	loff_t max_size = zi->i_max_size;
  
  	if (limit != RLIM_INFINITY) {
  		if (pos >= limit) {
  			send_sig(SIGXFSZ, current, 0);
  			return -EFBIG;
  		}
  		count = min(count, limit - pos);
  	}
  
  	if (!(file->f_flags & O_LARGEFILE))
  		max_size = min_t(loff_t, MAX_NON_LFS, max_size);
  
  	if (unlikely(pos >= max_size))
  		return -EFBIG;
  
  	return min(count, max_size - pos);
  }
  
  static ssize_t zonefs_write_checks(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	loff_t count;
  
  	if (IS_SWAPFILE(inode))
  		return -ETXTBSY;
  
  	if (!iov_iter_count(from))
  		return 0;
  
  	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
  		return -EINVAL;
  
  	if (iocb->ki_flags & IOCB_APPEND) {
  		if (zi->i_ztype != ZONEFS_ZTYPE_SEQ)
  			return -EINVAL;
  		mutex_lock(&zi->i_truncate_mutex);
  		iocb->ki_pos = zi->i_wpoffset;
  		mutex_unlock(&zi->i_truncate_mutex);
  	}
  
  	count = zonefs_write_check_limits(file, iocb->ki_pos,
  					  iov_iter_count(from));
  	if (count < 0)
  		return count;
  
  	iov_iter_truncate(from, count);
  	return iov_iter_count(from);
  }
  
  /*
   * Handle direct writes. For sequential zone files, this is the only possible
   * write path. For these files, check that the user is issuing writes
   * sequentially from the end of the file. This code assumes that the block layer
   * delivers write requests to the device in sequential order. This is always the
   * case if a block IO scheduler implementing the ELEVATOR_F_ZBD_SEQ_WRITE
   * elevator feature is being used (e.g. mq-deadline). The block layer always
   * automatically select such an elevator for zoned block devices during the
   * device initialization.
   */
  static ssize_t zonefs_file_dio_write(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	struct super_block *sb = inode->i_sb;
  	bool sync = is_sync_kiocb(iocb);
  	bool append = false;
  	ssize_t ret, count;
  
  	/*
  	 * For async direct IOs to sequential zone files, refuse IOCB_NOWAIT
  	 * as this can cause write reordering (e.g. the first aio gets EAGAIN
  	 * on the inode lock but the second goes through but is now unaligned).
  	 */
  	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ && !sync &&
  	    (iocb->ki_flags & IOCB_NOWAIT))
  		return -EOPNOTSUPP;
  
  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock(inode))
  			return -EAGAIN;
  	} else {
  		inode_lock(inode);
  	}
  
  	count = zonefs_write_checks(iocb, from);
  	if (count <= 0) {
  		ret = count;
  		goto inode_unlock;
  	}
  
  	if ((iocb->ki_pos | count) & (sb->s_blocksize - 1)) {
  		ret = -EINVAL;
  		goto inode_unlock;
  	}
  
  	/* Enforce sequential writes (append only) in sequential zones */
  	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ) {
  		mutex_lock(&zi->i_truncate_mutex);
  		if (iocb->ki_pos != zi->i_wpoffset) {
  			mutex_unlock(&zi->i_truncate_mutex);
  			ret = -EINVAL;
  			goto inode_unlock;
  		}
  		mutex_unlock(&zi->i_truncate_mutex);
  		append = sync;
  	}
  
  	if (append)
  		ret = zonefs_file_dio_append(iocb, from);
  	else
  		ret = iomap_dio_rw(iocb, from, &zonefs_iomap_ops,
  				   &zonefs_write_dio_ops, 0, 0);
  	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
  	    (ret > 0 || ret == -EIOCBQUEUED)) {
  		if (ret > 0)
  			count = ret;
  		mutex_lock(&zi->i_truncate_mutex);
  		zi->i_wpoffset += count;
  		mutex_unlock(&zi->i_truncate_mutex);
  	}
  
  inode_unlock:
  	inode_unlock(inode);
  
  	return ret;
  }
  
  static ssize_t zonefs_file_buffered_write(struct kiocb *iocb,
  					  struct iov_iter *from)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	ssize_t ret;
  
  	/*
  	 * Direct IO writes are mandatory for sequential zone files so that the
  	 * write IO issuing order is preserved.
  	 */
  	if (zi->i_ztype != ZONEFS_ZTYPE_CNV)
  		return -EIO;
  
  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock(inode))
  			return -EAGAIN;
  	} else {
  		inode_lock(inode);
  	}
  
  	ret = zonefs_write_checks(iocb, from);
  	if (ret <= 0)
  		goto inode_unlock;
  
  	ret = iomap_file_buffered_write(iocb, from, &zonefs_iomap_ops);
  	if (ret > 0)
  		iocb->ki_pos += ret;
  	else if (ret == -EIO)
  		zonefs_io_error(inode, true);
  
  inode_unlock:
  	inode_unlock(inode);
  	if (ret > 0)
  		ret = generic_write_sync(iocb, ret);
  
  	return ret;
  }
  
  static ssize_t zonefs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return -EPERM;
  
  	if (sb_rdonly(inode->i_sb))
  		return -EROFS;
  
  	/* Write operations beyond the zone size are not allowed */
  	if (iocb->ki_pos >= ZONEFS_I(inode)->i_max_size)
  		return -EFBIG;
  
  	if (iocb->ki_flags & IOCB_DIRECT) {
  		ssize_t ret = zonefs_file_dio_write(iocb, from);
  		if (ret != -ENOTBLK)
  			return ret;
  	}
  
  	return zonefs_file_buffered_write(iocb, from);
  }
  
  static int zonefs_file_read_dio_end_io(struct kiocb *iocb, ssize_t size,
  				       int error, unsigned int flags)
  {
  	if (error) {
  		zonefs_io_error(file_inode(iocb->ki_filp), false);
  		return error;
  	}
  
  	return 0;
  }
  
  static const struct iomap_dio_ops zonefs_read_dio_ops = {
  	.end_io			= zonefs_file_read_dio_end_io,
  };
  
  static ssize_t zonefs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	struct super_block *sb = inode->i_sb;
  	loff_t isize;
  	ssize_t ret;
  
  	/* Offline zones cannot be read */
  	if (unlikely(IS_IMMUTABLE(inode) && !(inode->i_mode & 0777)))
  		return -EPERM;
  
  	if (iocb->ki_pos >= zi->i_max_size)
  		return 0;
  
  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock_shared(inode))
  			return -EAGAIN;
  	} else {
  		inode_lock_shared(inode);
  	}
  
  	/* Limit read operations to written data */
  	mutex_lock(&zi->i_truncate_mutex);
  	isize = i_size_read(inode);
  	if (iocb->ki_pos >= isize) {
  		mutex_unlock(&zi->i_truncate_mutex);
  		ret = 0;
  		goto inode_unlock;
  	}
  	iov_iter_truncate(to, isize - iocb->ki_pos);
  	mutex_unlock(&zi->i_truncate_mutex);
  
  	if (iocb->ki_flags & IOCB_DIRECT) {
  		size_t count = iov_iter_count(to);
  
  		if ((iocb->ki_pos | count) & (sb->s_blocksize - 1)) {
  			ret = -EINVAL;
  			goto inode_unlock;
  		}
  		file_accessed(iocb->ki_filp);
  		ret = iomap_dio_rw(iocb, to, &zonefs_iomap_ops,
  				   &zonefs_read_dio_ops, 0, 0);
  	} else {
  		ret = generic_file_read_iter(iocb, to);
  		if (ret == -EIO)
  			zonefs_io_error(inode, false);
  	}
  
  inode_unlock:
  	inode_unlock_shared(inode);
  
  	return ret;
  }
  
  static inline bool zonefs_file_use_exp_open(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;
  
  	if (!(file->f_mode & FMODE_WRITE))
  		return false;
  
  	return true;
  }
  
  static int zonefs_open_zone(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;
  		}
  
  		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);
  				goto unlock;
  			}
  			zi->i_flags |= ZONEFS_ZONE_OPEN;
  		}
  	}
  
  	zi->i_wr_refcnt++;
  
  unlock:
  	mutex_unlock(&zi->i_truncate_mutex);
  
  	return ret;
  }
  
  static int zonefs_file_open(struct inode *inode, struct file *file)
  {
  	int ret;
  
  	ret = generic_file_open(inode, file);
  	if (ret)
  		return ret;
  
  	if (zonefs_file_use_exp_open(inode, file))
  		return zonefs_open_zone(inode);
  
  	return 0;
  }
  
  static void zonefs_close_zone(struct inode *inode)
  {
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  	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;
  
  		ret = zonefs_zone_mgmt(inode, REQ_OP_ZONE_CLOSE);
  		if (ret) {
  			__zonefs_io_error(inode, false);
  			/*
  			 * Leaving zones explicitly open may lead to a state
  			 * where most zones cannot be written (zone resources
  			 * exhausted). So take preventive action by remounting
  			 * read-only.
  			 */
  			if (zi->i_flags & ZONEFS_ZONE_OPEN &&
  			    !(sb->s_flags & SB_RDONLY)) {
  				zonefs_warn(sb, "closing zone failed, remounting filesystem read-only\n");
  				sb->s_flags |= SB_RDONLY;
  			}
  		}
  		zi->i_flags &= ~ZONEFS_ZONE_OPEN;
  dec:
  		atomic_dec(&sbi->s_open_zones);
  	}
  	mutex_unlock(&zi->i_truncate_mutex);
  }
  
  static int zonefs_file_release(struct inode *inode, struct file *file)
  {
  	/*
  	 * If we explicitly open a zone we must close it again as well, but the
  	 * zone management operation can fail (either due to an IO error or as
  	 * 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);
  
  	return 0;
  }
  
  static const struct file_operations zonefs_file_operations = {
  	.open		= zonefs_file_open,
  	.release	= zonefs_file_release,
  	.fsync		= zonefs_file_fsync,
  	.mmap		= zonefs_file_mmap,
  	.llseek		= zonefs_file_llseek,
  	.read_iter	= zonefs_file_read_iter,
  	.write_iter	= zonefs_file_write_iter,
  	.splice_read	= generic_file_splice_read,
  	.splice_write	= iter_file_splice_write,
  	.iopoll		= iocb_bio_iopoll,
  };
  
  static struct kmem_cache *zonefs_inode_cachep;
  
  static struct inode *zonefs_alloc_inode(struct super_block *sb)
  {
  	struct zonefs_inode_info *zi;
  
  	zi = kmem_cache_alloc(zonefs_inode_cachep, GFP_KERNEL);
  	if (!zi)
  		return NULL;
  
  	inode_init_once(&zi->i_vnode);
  	mutex_init(&zi->i_truncate_mutex);
  	zi->i_wr_refcnt = 0;
  
  	return &zi->i_vnode;
  }
  
  static void zonefs_free_inode(struct inode *inode)
  {
  	kmem_cache_free(zonefs_inode_cachep, ZONEFS_I(inode));
  }
  
  /*
   * File system stat.
   */
  static int zonefs_statfs(struct dentry *dentry, struct kstatfs *buf)
  {
  	struct super_block *sb = dentry->d_sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	enum zonefs_ztype t;
  
  	buf->f_type = ZONEFS_MAGIC;
  	buf->f_bsize = sb->s_blocksize;
  	buf->f_namelen = ZONEFS_NAME_MAX;
  
  	spin_lock(&sbi->s_lock);
  
  	buf->f_blocks = sbi->s_blocks;
  	if (WARN_ON(sbi->s_used_blocks > sbi->s_blocks))
  		buf->f_bfree = 0;
  	else
  		buf->f_bfree = buf->f_blocks - sbi->s_used_blocks;
  	buf->f_bavail = buf->f_bfree;
  
  	for (t = 0; t < ZONEFS_ZTYPE_MAX; t++) {
  		if (sbi->s_nr_files[t])
  			buf->f_files += sbi->s_nr_files[t] + 1;
  	}
  	buf->f_ffree = 0;
  
  	spin_unlock(&sbi->s_lock);
  
  	buf->f_fsid = uuid_to_fsid(sbi->s_uuid.b);
  
  	return 0;
  }
  
  enum {
  	Opt_errors_ro, Opt_errors_zro, Opt_errors_zol, Opt_errors_repair,
  	Opt_explicit_open, Opt_err,
  };
  
  static const match_table_t tokens = {
  	{ Opt_errors_ro,	"errors=remount-ro"},
  	{ Opt_errors_zro,	"errors=zone-ro"},
  	{ Opt_errors_zol,	"errors=zone-offline"},
  	{ Opt_errors_repair,	"errors=repair"},
  	{ Opt_explicit_open,	"explicit-open" },
  	{ Opt_err,		NULL}
  };
  
  static int zonefs_parse_options(struct super_block *sb, char *options)
  {
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	substring_t args[MAX_OPT_ARGS];
  	char *p;
  
  	if (!options)
  		return 0;
  
  	while ((p = strsep(&options, ",")) != NULL) {
  		int token;
  
  		if (!*p)
  			continue;
  
  		token = match_token(p, tokens, args);
  		switch (token) {
  		case Opt_errors_ro:
  			sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
  			sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_RO;
  			break;
  		case Opt_errors_zro:
  			sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
  			sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_ZRO;
  			break;
  		case Opt_errors_zol:
  			sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
  			sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_ZOL;
  			break;
  		case Opt_errors_repair:
  			sbi->s_mount_opts &= ~ZONEFS_MNTOPT_ERRORS_MASK;
  			sbi->s_mount_opts |= ZONEFS_MNTOPT_ERRORS_REPAIR;
  			break;
  		case Opt_explicit_open:
  			sbi->s_mount_opts |= ZONEFS_MNTOPT_EXPLICIT_OPEN;
  			break;
  		default:
  			return -EINVAL;
  		}
  	}
  
  	return 0;
  }
  
  static int zonefs_show_options(struct seq_file *seq, struct dentry *root)
  {
  	struct zonefs_sb_info *sbi = ZONEFS_SB(root->d_sb);
  
  	if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_RO)
  		seq_puts(seq, ",errors=remount-ro");
  	if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZRO)
  		seq_puts(seq, ",errors=zone-ro");
  	if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZOL)
  		seq_puts(seq, ",errors=zone-offline");
  	if (sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_REPAIR)
  		seq_puts(seq, ",errors=repair");
  
  	return 0;
  }
  
  static int zonefs_remount(struct super_block *sb, int *flags, char *data)
  {
  	sync_filesystem(sb);
  
  	return zonefs_parse_options(sb, data);
  }
  
  static const struct super_operations zonefs_sops = {
  	.alloc_inode	= zonefs_alloc_inode,
  	.free_inode	= zonefs_free_inode,
  	.statfs		= zonefs_statfs,
  	.remount_fs	= zonefs_remount,
  	.show_options	= zonefs_show_options,
  };
  
  static const struct inode_operations zonefs_dir_inode_operations = {
  	.lookup		= simple_lookup,
  	.setattr	= zonefs_inode_setattr,
  };
  
  static void zonefs_init_dir_inode(struct inode *parent, struct inode *inode,
  				  enum zonefs_ztype type)
  {
  	struct super_block *sb = parent->i_sb;
  
  	inode->i_ino = blkdev_nr_zones(sb->s_bdev->bd_disk) + type + 1;
  	inode_init_owner(&init_user_ns, inode, parent, S_IFDIR | 0555);
  	inode->i_op = &zonefs_dir_inode_operations;
  	inode->i_fop = &simple_dir_operations;
  	set_nlink(inode, 2);
  	inc_nlink(parent);
  }
  
  static void zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
  				   enum zonefs_ztype type)
  {
  	struct super_block *sb = inode->i_sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	struct zonefs_inode_info *zi = ZONEFS_I(inode);
  
  	inode->i_ino = zone->start >> sbi->s_zone_sectors_shift;
  	inode->i_mode = S_IFREG | sbi->s_perm;
  
  	zi->i_ztype = type;
  	zi->i_zsector = zone->start;
  	zi->i_zone_size = zone->len << SECTOR_SHIFT;
  
  	zi->i_max_size = min_t(loff_t, MAX_LFS_FILESIZE,
  			       zone->capacity << SECTOR_SHIFT);
  	zi->i_wpoffset = zonefs_check_zone_condition(inode, zone, true, true);
  
  	inode->i_uid = sbi->s_uid;
  	inode->i_gid = sbi->s_gid;
  	inode->i_size = zi->i_wpoffset;
  	inode->i_blocks = zi->i_max_size >> SECTOR_SHIFT;
  
  	inode->i_op = &zonefs_file_inode_operations;
  	inode->i_fop = &zonefs_file_operations;
  	inode->i_mapping->a_ops = &zonefs_file_aops;
  
  	sb->s_maxbytes = max(zi->i_max_size, sb->s_maxbytes);
  	sbi->s_blocks += zi->i_max_size >> sb->s_blocksize_bits;
  	sbi->s_used_blocks += zi->i_wpoffset >> sb->s_blocksize_bits;
  }
  
  static struct dentry *zonefs_create_inode(struct dentry *parent,
  					const char *name, struct blk_zone *zone,
  					enum zonefs_ztype type)
  {
  	struct inode *dir = d_inode(parent);
  	struct dentry *dentry;
  	struct inode *inode;
  
  	dentry = d_alloc_name(parent, name);
  	if (!dentry)
  		return NULL;
  
  	inode = new_inode(parent->d_sb);
  	if (!inode)
  		goto dput;
  
  	inode->i_ctime = inode->i_mtime = inode->i_atime = dir->i_ctime;
  	if (zone)
  		zonefs_init_file_inode(inode, zone, type);
  	else
  		zonefs_init_dir_inode(dir, inode, type);
  	d_add(dentry, inode);
  	dir->i_size++;
  
  	return dentry;
  
  dput:
  	dput(dentry);
  
  	return NULL;
  }
  
  struct zonefs_zone_data {
  	struct super_block	*sb;
  	unsigned int		nr_zones[ZONEFS_ZTYPE_MAX];
  	struct blk_zone		*zones;
  };
  
  /*
   * Create a zone group and populate it with zone files.
   */
  static int zonefs_create_zgroup(struct zonefs_zone_data *zd,
  				enum zonefs_ztype type)
  {
  	struct super_block *sb = zd->sb;
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	struct blk_zone *zone, *next, *end;
  	const char *zgroup_name;
  	char *file_name;
  	struct dentry *dir;
  	unsigned int n = 0;
  	int ret;
  
  	/* If the group is empty, there is nothing to do */
  	if (!zd->nr_zones[type])
  		return 0;
  
  	file_name = kmalloc(ZONEFS_NAME_MAX, GFP_KERNEL);
  	if (!file_name)
  		return -ENOMEM;
  
  	if (type == ZONEFS_ZTYPE_CNV)
  		zgroup_name = "cnv";
  	else
  		zgroup_name = "seq";
  
  	dir = zonefs_create_inode(sb->s_root, zgroup_name, NULL, type);
  	if (!dir) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	/*
  	 * The first zone contains the super block: skip it.
  	 */
  	end = zd->zones + blkdev_nr_zones(sb->s_bdev->bd_disk);
  	for (zone = &zd->zones[1]; zone < end; zone = next) {
  
  		next = zone + 1;
  		if (zonefs_zone_type(zone) != type)
  			continue;
  
  		/*
  		 * For conventional zones, contiguous zones can be aggregated
  		 * together to form larger files. Note that this overwrites the
  		 * length of the first zone of the set of contiguous zones
  		 * aggregated together. If one offline or read-only zone is
  		 * found, assume that all zones aggregated have the same
  		 * condition.
  		 */
  		if (type == ZONEFS_ZTYPE_CNV &&
  		    (sbi->s_features & ZONEFS_F_AGGRCNV)) {
  			for (; next < end; next++) {
  				if (zonefs_zone_type(next) != type)
  					break;
  				zone->len += next->len;
  				zone->capacity += next->capacity;
  				if (next->cond == BLK_ZONE_COND_READONLY &&
  				    zone->cond != BLK_ZONE_COND_OFFLINE)
  					zone->cond = BLK_ZONE_COND_READONLY;
  				else if (next->cond == BLK_ZONE_COND_OFFLINE)
  					zone->cond = BLK_ZONE_COND_OFFLINE;
  			}
  			if (zone->capacity != zone->len) {
  				zonefs_err(sb, "Invalid conventional zone capacity\n");
  				ret = -EINVAL;
  				goto free;
  			}
  		}
  
  		/*
  		 * Use the file number within its group as file name.
  		 */
  		snprintf(file_name, ZONEFS_NAME_MAX - 1, "%u", n);
  		if (!zonefs_create_inode(dir, file_name, zone, type)) {
  			ret = -ENOMEM;
  			goto free;
  		}
  
  		n++;
  	}
  
  	zonefs_info(sb, "Zone group \"%s\" has %u file%s\n",
  		    zgroup_name, n, n > 1 ? "s" : "");
  
  	sbi->s_nr_files[type] = n;
  	ret = 0;
  
  free:
  	kfree(file_name);
  
  	return ret;
  }
  
  static int zonefs_get_zone_info_cb(struct blk_zone *zone, unsigned int idx,
  				   void *data)
  {
  	struct zonefs_zone_data *zd = data;
  
  	/*
  	 * Count the number of usable zones: the first zone at index 0 contains
  	 * the super block and is ignored.
  	 */
  	switch (zone->type) {
  	case BLK_ZONE_TYPE_CONVENTIONAL:
  		zone->wp = zone->start + zone->len;
  		if (idx)
  			zd->nr_zones[ZONEFS_ZTYPE_CNV]++;
  		break;
  	case BLK_ZONE_TYPE_SEQWRITE_REQ:
  	case BLK_ZONE_TYPE_SEQWRITE_PREF:
  		if (idx)
  			zd->nr_zones[ZONEFS_ZTYPE_SEQ]++;
  		break;
  	default:
  		zonefs_err(zd->sb, "Unsupported zone type 0x%x\n",
  			   zone->type);
  		return -EIO;
  	}
  
  	memcpy(&zd->zones[idx], zone, sizeof(struct blk_zone));
  
  	return 0;
  }
  
  static int zonefs_get_zone_info(struct zonefs_zone_data *zd)
  {
  	struct block_device *bdev = zd->sb->s_bdev;
  	int ret;
  
  	zd->zones = kvcalloc(blkdev_nr_zones(bdev->bd_disk),
  			     sizeof(struct blk_zone), GFP_KERNEL);
  	if (!zd->zones)
  		return -ENOMEM;
  
  	/* Get zones information from the device */
  	ret = blkdev_report_zones(bdev, 0, BLK_ALL_ZONES,
  				  zonefs_get_zone_info_cb, zd);
  	if (ret < 0) {
  		zonefs_err(zd->sb, "Zone report failed %d\n", ret);
  		return ret;
  	}
  
  	if (ret != blkdev_nr_zones(bdev->bd_disk)) {
  		zonefs_err(zd->sb, "Invalid zone report (%d/%u zones)\n",
  			   ret, blkdev_nr_zones(bdev->bd_disk));
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static inline void zonefs_cleanup_zone_info(struct zonefs_zone_data *zd)
  {
  	kvfree(zd->zones);
  }
  
  /*
   * Read super block information from the device.
   */
  static int zonefs_read_super(struct super_block *sb)
  {
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  	struct zonefs_super *super;
  	u32 crc, stored_crc;
  	struct page *page;
  	struct bio_vec bio_vec;
  	struct bio bio;
  	int ret;
  
  	page = alloc_page(GFP_KERNEL);
  	if (!page)
  		return -ENOMEM;
  
  	bio_init(&bio, &bio_vec, 1);
  	bio.bi_iter.bi_sector = 0;
  	bio.bi_opf = REQ_OP_READ;
  	bio_set_dev(&bio, sb->s_bdev);
  	bio_add_page(&bio, page, PAGE_SIZE, 0);
  
  	ret = submit_bio_wait(&bio);
  	if (ret)
  		goto free_page;
  
  	super = kmap(page);
  
  	ret = -EINVAL;
  	if (le32_to_cpu(super->s_magic) != ZONEFS_MAGIC)
  		goto unmap;
  
  	stored_crc = le32_to_cpu(super->s_crc);
  	super->s_crc = 0;
  	crc = crc32(~0U, (unsigned char *)super, sizeof(struct zonefs_super));
  	if (crc != stored_crc) {
  		zonefs_err(sb, "Invalid checksum (Expected 0x%08x, got 0x%08x)",
  			   crc, stored_crc);
  		goto unmap;
  	}
  
  	sbi->s_features = le64_to_cpu(super->s_features);
  	if (sbi->s_features & ~ZONEFS_F_DEFINED_FEATURES) {
  		zonefs_err(sb, "Unknown features set 0x%llx\n",
  			   sbi->s_features);
  		goto unmap;
  	}
  
  	if (sbi->s_features & ZONEFS_F_UID) {
  		sbi->s_uid = make_kuid(current_user_ns(),
  				       le32_to_cpu(super->s_uid));
  		if (!uid_valid(sbi->s_uid)) {
  			zonefs_err(sb, "Invalid UID feature\n");
  			goto unmap;
  		}
  	}
  
  	if (sbi->s_features & ZONEFS_F_GID) {
  		sbi->s_gid = make_kgid(current_user_ns(),
  				       le32_to_cpu(super->s_gid));
  		if (!gid_valid(sbi->s_gid)) {
  			zonefs_err(sb, "Invalid GID feature\n");
  			goto unmap;
  		}
  	}
  
  	if (sbi->s_features & ZONEFS_F_PERM)
  		sbi->s_perm = le32_to_cpu(super->s_perm);
  
  	if (memchr_inv(super->s_reserved, 0, sizeof(super->s_reserved))) {
  		zonefs_err(sb, "Reserved area is being used\n");
  		goto unmap;
  	}
  
  	import_uuid(&sbi->s_uuid, super->s_uuid);
  	ret = 0;
  
  unmap:
  	kunmap(page);
  free_page:
  	__free_page(page);
  
  	return ret;
  }
  
  /*
   * Check that the device is zoned. If it is, get the list of zones and create
   * sub-directories and files according to the device zone configuration and
   * format options.
   */
  static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct zonefs_zone_data zd;
  	struct zonefs_sb_info *sbi;
  	struct inode *inode;
  	enum zonefs_ztype t;
  	int ret;
  
  	if (!bdev_is_zoned(sb->s_bdev)) {
  		zonefs_err(sb, "Not a zoned block device\n");
  		return -EINVAL;
  	}
  
  	/*
  	 * Initialize super block information: the maximum file size is updated
  	 * when the zone files are created so that the format option
  	 * ZONEFS_F_AGGRCNV which increases the maximum file size of a file
  	 * beyond the zone size is taken into account.
  	 */
  	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
  	if (!sbi)
  		return -ENOMEM;
  
  	spin_lock_init(&sbi->s_lock);
  	sb->s_fs_info = sbi;
  	sb->s_magic = ZONEFS_MAGIC;
  	sb->s_maxbytes = 0;
  	sb->s_op = &zonefs_sops;
  	sb->s_time_gran	= 1;
  
  	/*
  	 * The block size is set to the device zone write granularity to ensure
  	 * that write operations are always aligned according to the device
  	 * interface constraints.
  	 */
  	sb_set_blocksize(sb, bdev_zone_write_granularity(sb->s_bdev));
  	sbi->s_zone_sectors_shift = ilog2(bdev_zone_sectors(sb->s_bdev));
  	sbi->s_uid = GLOBAL_ROOT_UID;
  	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 &&
  	    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;
  	}
  
  	ret = zonefs_read_super(sb);
  	if (ret)
  		return ret;
  
  	ret = zonefs_parse_options(sb, data);
  	if (ret)
  		return ret;
  
  	memset(&zd, 0, sizeof(struct zonefs_zone_data));
  	zd.sb = sb;
  	ret = zonefs_get_zone_info(&zd);
  	if (ret)
  		goto cleanup;
  
  	zonefs_info(sb, "Mounting %u zones",
  		    blkdev_nr_zones(sb->s_bdev->bd_disk));
  
  	/* Create root directory inode */
  	ret = -ENOMEM;
  	inode = new_inode(sb);
  	if (!inode)
  		goto cleanup;
  
  	inode->i_ino = blkdev_nr_zones(sb->s_bdev->bd_disk);
  	inode->i_mode = S_IFDIR | 0555;
  	inode->i_ctime = inode->i_mtime = inode->i_atime = current_time(inode);
  	inode->i_op = &zonefs_dir_inode_operations;
  	inode->i_fop = &simple_dir_operations;
  	set_nlink(inode, 2);
  
  	sb->s_root = d_make_root(inode);
  	if (!sb->s_root)
  		goto cleanup;
  
  	/* Create and populate files in zone groups directories */
  	for (t = 0; t < ZONEFS_ZTYPE_MAX; t++) {
  		ret = zonefs_create_zgroup(&zd, t);
  		if (ret)
  			break;
  	}
  
  cleanup:
  	zonefs_cleanup_zone_info(&zd);
  
  	return ret;
  }
  
  static struct dentry *zonefs_mount(struct file_system_type *fs_type,
  				   int flags, const char *dev_name, void *data)
  {
  	return mount_bdev(fs_type, flags, dev_name, data, zonefs_fill_super);
  }
  
  static void zonefs_kill_super(struct super_block *sb)
  {
  	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
  
  	if (sb->s_root)
  		d_genocide(sb->s_root);
  	kill_block_super(sb);
  	kfree(sbi);
  }
  
  /*
   * File system definition and registration.
   */
  static struct file_system_type zonefs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "zonefs",
  	.mount		= zonefs_mount,
  	.kill_sb	= zonefs_kill_super,
  	.fs_flags	= FS_REQUIRES_DEV,
  };
  
  static int __init zonefs_init_inodecache(void)
  {
  	zonefs_inode_cachep = kmem_cache_create("zonefs_inode_cache",
  			sizeof(struct zonefs_inode_info), 0,
  			(SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | SLAB_ACCOUNT),
  			NULL);
  	if (zonefs_inode_cachep == NULL)
  		return -ENOMEM;
  	return 0;
  }
  
  static void zonefs_destroy_inodecache(void)
  {
  	/*
  	 * Make sure all delayed rcu free inodes are flushed before we
  	 * destroy the inode cache.
  	 */
  	rcu_barrier();
  	kmem_cache_destroy(zonefs_inode_cachep);
  }
  
  static int __init zonefs_init(void)
  {
  	int ret;
  
  	BUILD_BUG_ON(sizeof(struct zonefs_super) != ZONEFS_SUPER_SIZE);
  
  	ret = zonefs_init_inodecache();
  	if (ret)
  		return ret;
  
  	ret = register_filesystem(&zonefs_type);
  	if (ret) {
  		zonefs_destroy_inodecache();
  		return ret;
  	}
  
  	return 0;
  }
  
  static void __exit zonefs_exit(void)
  {
  	zonefs_destroy_inodecache();
  	unregister_filesystem(&zonefs_type);
  }
  
  MODULE_AUTHOR("Damien Le Moal");
  MODULE_DESCRIPTION("Zone file system for zoned block devices");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_FS("zonefs");
  module_init(zonefs_init);
  module_exit(zonefs_exit);
  