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Commit 2d9b1d69 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'xfs-4.16-fixes-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux 

Pull xfs fixes from Darrick Wong:

 - Fix some iomap locking problems

 - Don't allocate cow blocks when we're zeroing file data

* tag 'xfs-4.16-fixes-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: don't block on the ilock for RWF_NOWAIT
  xfs: don't start out with the exclusive ilock for direct I/O
  xfs: don't allocate COW blocks for zeroing holes or unwritten extents
parents a525df05 ff3d8b9c

fs/xfs/xfs_iomap.c

+30 −12
Original line number Diff line number Diff line
@@ -955,15 +955,29 @@ static inline bool imap_needs_alloc(struct inode *inode, 
		(IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);

}



static inline bool needs_cow_for_zeroing(struct xfs_bmbt_irec *imap, int nimaps)

{

	return nimaps &&

		imap->br_startblock != HOLESTARTBLOCK &&

		imap->br_state != XFS_EXT_UNWRITTEN;

}



static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags)

{

	/*

	 * COW writes will allocate delalloc space, so we need to make sure

	 * to take the lock exclusively here.

	 * COW writes may allocate delalloc space or convert unwritten COW

	 * extents, so we need to make sure to take the lock exclusively here.

	 */

	if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO)))

		return true;

	if ((flags & IOMAP_DIRECT) && (flags & IOMAP_WRITE))



	/*

	 * Extents not yet cached requires exclusive access, don't block.

	 * This is an opencoded xfs_ilock_data_map_shared() to cater for the

	 * non-blocking behaviour.

	 */

	if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE &&

	    !(ip->i_df.if_flags & XFS_IFEXTENTS))

		return true;

	return false;

}
@@ -993,16 +1007,18 @@ xfs_file_iomap_begin( 
		return xfs_file_iomap_begin_delay(inode, offset, length, iomap);

	}



	if (need_excl_ilock(ip, flags)) {

	if (need_excl_ilock(ip, flags))

		lockmode = XFS_ILOCK_EXCL;

		xfs_ilock(ip, XFS_ILOCK_EXCL);

	} else {

		lockmode = xfs_ilock_data_map_shared(ip);

	}

	else

		lockmode = XFS_ILOCK_SHARED;



	if ((flags & IOMAP_NOWAIT) && !(ip->i_df.if_flags & XFS_IFEXTENTS)) {

		error = -EAGAIN;

		goto out_unlock;

	if (flags & IOMAP_NOWAIT) {

		if (!(ip->i_df.if_flags & XFS_IFEXTENTS))

			return -EAGAIN;

		if (!xfs_ilock_nowait(ip, lockmode))

			return -EAGAIN;

	} else {

		xfs_ilock(ip, lockmode);

	}



	ASSERT(offset <= mp->m_super->s_maxbytes);
@@ -1024,7 +1040,9 @@ xfs_file_iomap_begin( 
			goto out_unlock;

	}



	if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {

	if (xfs_is_reflink_inode(ip) &&

	    ((flags & IOMAP_WRITE) ||

	     ((flags & IOMAP_ZERO) && needs_cow_for_zeroing(&imap, nimaps)))) {

		if (flags & IOMAP_DIRECT) {

			/*

			 * A reflinked inode will result in CoW alloc.