text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (c) 2014 Christoph Hellwig.
   */
  #include "xfs.h"
  #include "xfs_shared.h"
  #include "xfs_format.h"
  #include "xfs_log_format.h"
  #include "xfs_trans_resv.h"
  #include "xfs_mount.h"
  #include "xfs_inode.h"
  #include "xfs_trans.h"
  #include "xfs_bmap.h"
  #include "xfs_iomap.h"
  
  /*
   * Ensure that we do not have any outstanding pNFS layouts that can be used by
   * clients to directly read from or write to this inode.  This must be called
   * before every operation that can remove blocks from the extent map.
   * Additionally we call it during the write operation, where aren't concerned
   * about exposing unallocated blocks but just want to provide basic
   * synchronization between a local writer and pNFS clients.  mmap writes would
   * also benefit from this sort of synchronization, but due to the tricky locking
   * rules in the page fault path we don't bother.
   */
  int
  xfs_break_leased_layouts(
  	struct inode		*inode,
  	uint			*iolock,
  	bool			*did_unlock)
  {
  	struct xfs_inode	*ip = XFS_I(inode);
  	int			error;
  
  	while ((error = break_layout(inode, false)) == -EWOULDBLOCK) {
  		xfs_iunlock(ip, *iolock);
  		*did_unlock = true;
  		error = break_layout(inode, true);
  		*iolock &= ~XFS_IOLOCK_SHARED;
  		*iolock |= XFS_IOLOCK_EXCL;
  		xfs_ilock(ip, *iolock);
  	}
  
  	return error;
  }
  
  /*
   * Get a unique ID including its location so that the client can identify
   * the exported device.
   */
  int
  xfs_fs_get_uuid(
  	struct super_block	*sb,
  	u8			*buf,
  	u32			*len,
  	u64			*offset)
  {
  	struct xfs_mount	*mp = XFS_M(sb);
  
  	printk_once(KERN_NOTICE
  "XFS (%s): using experimental pNFS feature, use at your own risk!\n",
  		mp->m_fsname);
  
  	if (*len < sizeof(uuid_t))
  		return -EINVAL;
  
  	memcpy(buf, &mp->m_sb.sb_uuid, sizeof(uuid_t));
  	*len = sizeof(uuid_t);
  	*offset = offsetof(struct xfs_dsb, sb_uuid);
  	return 0;
  }
  
  /*
   * Get a layout for the pNFS client.
   */
  int
  xfs_fs_map_blocks(
  	struct inode		*inode,
  	loff_t			offset,
  	u64			length,
  	struct iomap		*iomap,
  	bool			write,
  	u32			*device_generation)
  {
  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_bmbt_irec	imap;
  	xfs_fileoff_t		offset_fsb, end_fsb;
  	loff_t			limit;
  	int			bmapi_flags = XFS_BMAPI_ENTIRE;
  	int			nimaps = 1;
  	uint			lock_flags;
  	int			error = 0;
  
  	if (XFS_FORCED_SHUTDOWN(mp))
  		return -EIO;
  
  	/*
  	 * We can't export inodes residing on the realtime device.  The realtime
  	 * device doesn't have a UUID to identify it, so the client has no way
  	 * to find it.
  	 */
  	if (XFS_IS_REALTIME_INODE(ip))
  		return -ENXIO;
  
  	/*
  	 * The pNFS block layout spec actually supports reflink like
  	 * functionality, but the Linux pNFS server doesn't implement it yet.
  	 */
  	if (xfs_is_reflink_inode(ip))
  		return -ENXIO;
  
  	/*
  	 * Lock out any other I/O before we flush and invalidate the pagecache,
  	 * and then hand out a layout to the remote system.  This is very
  	 * similar to direct I/O, except that the synchronization is much more
  	 * complicated.  See the comment near xfs_break_leased_layouts
  	 * for a detailed explanation.
  	 */
  	xfs_ilock(ip, XFS_IOLOCK_EXCL);
  
  	error = -EINVAL;
  	limit = mp->m_super->s_maxbytes;
  	if (!write)
  		limit = max(limit, round_up(i_size_read(inode),
  				     inode->i_sb->s_blocksize));
  	if (offset > limit)
  		goto out_unlock;
  	if (offset > limit - length)
  		length = limit - offset;
  
  	error = filemap_write_and_wait(inode->i_mapping);
  	if (error)
  		goto out_unlock;
  	error = invalidate_inode_pages2(inode->i_mapping);
  	if (WARN_ON_ONCE(error))
  		return error;
  
  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + length);
  	offset_fsb = XFS_B_TO_FSBT(mp, offset);
  
  	lock_flags = xfs_ilock_data_map_shared(ip);
  	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
  				&imap, &nimaps, bmapi_flags);
  	xfs_iunlock(ip, lock_flags);
  
  	if (error)
  		goto out_unlock;
  
  	if (write) {
  		enum xfs_prealloc_flags	flags = 0;
  
  		ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
  
  		if (!nimaps || imap.br_startblock == HOLESTARTBLOCK) {
  			/*
  			 * xfs_iomap_write_direct() expects to take ownership of
  			 * the shared ilock.
  			 */
  			xfs_ilock(ip, XFS_ILOCK_SHARED);
  			error = xfs_iomap_write_direct(ip, offset, length,
  						       &imap, nimaps);
  			if (error)
  				goto out_unlock;
  
  			/*
  			 * Ensure the next transaction is committed
  			 * synchronously so that the blocks allocated and
  			 * handed out to the client are guaranteed to be
  			 * present even after a server crash.
  			 */
  			flags |= XFS_PREALLOC_SET | XFS_PREALLOC_SYNC;
  		}
  
  		error = xfs_update_prealloc_flags(ip, flags);
  		if (error)
  			goto out_unlock;
  	}
  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
  
  	error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
  	*device_generation = mp->m_generation;
  	return error;
  out_unlock:
  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
  	return error;
  }
  
  /*
   * Ensure the size update falls into a valid allocated block.
   */
  static int
  xfs_pnfs_validate_isize(
  	struct xfs_inode	*ip,
  	xfs_off_t		isize)
  {
  	struct xfs_bmbt_irec	imap;
  	int			nimaps = 1;
  	int			error = 0;
  
  	xfs_ilock(ip, XFS_ILOCK_SHARED);
  	error = xfs_bmapi_read(ip, XFS_B_TO_FSBT(ip->i_mount, isize - 1), 1,
  				&imap, &nimaps, 0);
  	xfs_iunlock(ip, XFS_ILOCK_SHARED);
  	if (error)
  		return error;
  
  	if (imap.br_startblock == HOLESTARTBLOCK ||
  	    imap.br_startblock == DELAYSTARTBLOCK ||
  	    imap.br_state == XFS_EXT_UNWRITTEN)
  		return -EIO;
  	return 0;
  }
  
  /*
   * Make sure the blocks described by maps are stable on disk.  This includes
   * converting any unwritten extents, flushing the disk cache and updating the
   * time stamps.
   *
   * Note that we rely on the caller to always send us a timestamp update so that
   * we always commit a transaction here.  If that stops being true we will have
   * to manually flush the cache here similar to what the fsync code path does
   * for datasyncs on files that have no dirty metadata.
   */
  int
  xfs_fs_commit_blocks(
  	struct inode		*inode,
  	struct iomap		*maps,
  	int			nr_maps,
  	struct iattr		*iattr)
  {
  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_trans	*tp;
  	bool			update_isize = false;
  	int			error, i;
  	loff_t			size;
  
  	ASSERT(iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME));
  
  	xfs_ilock(ip, XFS_IOLOCK_EXCL);
  
  	size = i_size_read(inode);
  	if ((iattr->ia_valid & ATTR_SIZE) && iattr->ia_size > size) {
  		update_isize = true;
  		size = iattr->ia_size;
  	}
  
  	for (i = 0; i < nr_maps; i++) {
  		u64 start, length, end;
  
  		start = maps[i].offset;
  		if (start > size)
  			continue;
  
  		end = start + maps[i].length;
  		if (end > size)
  			end = size;
  
  		length = end - start;
  		if (!length)
  			continue;
  	
  		/*
  		 * Make sure reads through the pagecache see the new data.
  		 */
  		error = invalidate_inode_pages2_range(inode->i_mapping,
  					start >> PAGE_SHIFT,
  					(end - 1) >> PAGE_SHIFT);
  		WARN_ON_ONCE(error);
  
  		error = xfs_iomap_write_unwritten(ip, start, length, false);
  		if (error)
  			goto out_drop_iolock;
  	}
  
  	if (update_isize) {
  		error = xfs_pnfs_validate_isize(ip, size);
  		if (error)
  			goto out_drop_iolock;
  	}
  
  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
  	if (error)
  		goto out_drop_iolock;
  
  	xfs_ilock(ip, XFS_ILOCK_EXCL);
  	xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
  	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
  
  	xfs_setattr_time(ip, iattr);
  	if (update_isize) {
  		i_size_write(inode, iattr->ia_size);
  		ip->i_d.di_size = iattr->ia_size;
  	}
  
  	xfs_trans_set_sync(tp);
  	error = xfs_trans_commit(tp);
  
  out_drop_iolock:
  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
  	return error;
  }
  