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Commit 26b91c72 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
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xfs: make COW fork unwritten extent conversions more robust 



If we have racing buffered and direct I/O COW fork extents under
writeback can have been moved to the data fork by the time we call
xfs_reflink_convert_cow from xfs_submit_ioend.  This would be mostly
harmless as the block numbers don't change by this move, except for
the fact that xfs_bmapi_write will crash or trigger asserts when
not finding existing extents, even despite trying to paper over this
with the XFS_BMAPI_CONVERT_ONLY flag.

Instead of special casing non-transaction conversions in the already
way too complicated xfs_bmapi_write just add a new helper for the much
simpler non-transactional COW fork case, which simplify ignores not
found extents.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent db46e604

fs/xfs/libxfs/xfs_bmap.c

+3 −6
Original line number Diff line number Diff line
@@ -2031,7 +2031,7 @@ xfs_bmap_add_extent_delay_real( 
/*

 * Convert an unwritten allocation to a real allocation or vice versa.

 */

STATIC int				/* error */

int					/* error */

xfs_bmap_add_extent_unwritten_real(

	struct xfs_trans	*tp,

	xfs_inode_t		*ip,	/* incore inode pointer */
@@ -4276,9 +4276,7 @@ xfs_bmapi_write( 


	ASSERT(*nmap >= 1);

	ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);

	ASSERT(tp != NULL ||

	       (flags & (XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK)) ==

			(XFS_BMAPI_CONVERT | XFS_BMAPI_COWFORK));

	ASSERT(tp != NULL);

	ASSERT(len > 0);

	ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_LOCAL);

	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
@@ -4352,8 +4350,7 @@ xfs_bmapi_write( 
		 * First, deal with the hole before the allocated space

		 * that we found, if any.

		 */

		if ((need_alloc || wasdelay) &&

		    !(flags & XFS_BMAPI_CONVERT_ONLY)) {

		if (need_alloc || wasdelay) {

			bma.eof = eof;

			bma.conv = !!(flags & XFS_BMAPI_CONVERT);

			bma.wasdel = wasdelay;

fs/xfs/libxfs/xfs_bmap.h

+4 −4
Original line number Diff line number Diff line
@@ -95,9 +95,6 @@ struct xfs_extent_free_item 
/* Map something in the CoW fork. */

#define XFS_BMAPI_COWFORK	0x200



/* Only convert unwritten extents, don't allocate new blocks */

#define XFS_BMAPI_CONVERT_ONLY	0x800



/* Skip online discard of freed extents */

#define XFS_BMAPI_NODISCARD	0x1000
@@ -114,7 +111,6 @@ struct xfs_extent_free_item 
	{ XFS_BMAPI_ZERO,	"ZERO" }, \

	{ XFS_BMAPI_REMAP,	"REMAP" }, \

	{ XFS_BMAPI_COWFORK,	"COWFORK" }, \

	{ XFS_BMAPI_CONVERT_ONLY, "CONVERT_ONLY" }, \

	{ XFS_BMAPI_NODISCARD,	"NODISCARD" }, \

	{ XFS_BMAPI_NORMAP,	"NORMAP" }
@@ -226,6 +222,10 @@ int xfs_bmapi_reserve_delalloc(struct xfs_inode *ip, int whichfork, 
int	xfs_bmapi_convert_delalloc(struct xfs_inode *ip, int whichfork,

		xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap,

		unsigned int *seq);

int	xfs_bmap_add_extent_unwritten_real(struct xfs_trans *tp,

		struct xfs_inode *ip, int whichfork,

		struct xfs_iext_cursor *icur, struct xfs_btree_cur **curp,

		struct xfs_bmbt_irec *new, int *logflagsp);



static inline void

xfs_bmap_add_free(

fs/xfs/xfs_reflink.c

+38 −23
Original line number Diff line number Diff line
@@ -234,26 +234,42 @@ xfs_reflink_trim_around_shared( 
	}

}



/* Convert part of an unwritten CoW extent to a real one. */

STATIC int

xfs_reflink_convert_cow_extent(

static int

xfs_reflink_convert_cow_locked(

	struct xfs_inode	*ip,

	struct xfs_bmbt_irec		*imap,

	xfs_fileoff_t		offset_fsb,

	xfs_filblks_t		count_fsb)

{

	int				nimaps = 1;

	struct xfs_iext_cursor	icur;

	struct xfs_bmbt_irec	got;

	struct xfs_btree_cur	*dummy_cur = NULL;

	int			dummy_logflags;

	int			error;



	if (imap->br_state == XFS_EXT_NORM)

	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))

		return 0;



	xfs_trim_extent(imap, offset_fsb, count_fsb);

	trace_xfs_reflink_convert_cow(ip, imap);

	if (imap->br_blockcount == 0)

		return 0;

	return xfs_bmapi_write(NULL, ip, imap->br_startoff, imap->br_blockcount,

			XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT, 0, imap,

			&nimaps);

	do {

		if (got.br_startoff >= offset_fsb + count_fsb)

			break;

		if (got.br_state == XFS_EXT_NORM)

			continue;

		if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))

			return -EIO;



		xfs_trim_extent(&got, offset_fsb, count_fsb);

		if (!got.br_blockcount)

			continue;



		got.br_state = XFS_EXT_NORM;

		error = xfs_bmap_add_extent_unwritten_real(NULL, ip,

				XFS_COW_FORK, &icur, &dummy_cur, &got,

				&dummy_logflags);

		if (error)

			return error;

	} while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));



	return error;

}



/* Convert all of the unwritten CoW extents in a file's range to real ones. */
@@ -267,15 +283,12 @@ xfs_reflink_convert_cow( 
	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);

	xfs_fileoff_t		end_fsb = XFS_B_TO_FSB(mp, offset + count);

	xfs_filblks_t		count_fsb = end_fsb - offset_fsb;

	struct xfs_bmbt_irec	imap;

	int			nimaps = 1, error = 0;

	int			error;



	ASSERT(count != 0);



	xfs_ilock(ip, XFS_ILOCK_EXCL);

	error = xfs_bmapi_write(NULL, ip, offset_fsb, count_fsb,

			XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT |

			XFS_BMAPI_CONVERT_ONLY, 0, &imap, &nimaps);

	error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);

	xfs_iunlock(ip, XFS_ILOCK_EXCL);

	return error;

}
@@ -405,14 +418,16 @@ xfs_reflink_allocate_cow( 
	if (nimaps == 0)

		return -ENOSPC;

convert:

	xfs_trim_extent(imap, offset_fsb, count_fsb);

	/*

	 * COW fork extents are supposed to remain unwritten until we're ready

	 * to initiate a disk write.  For direct I/O we are going to write the

	 * data and need the conversion, but for buffered writes we're done.

	 */

	if (!(iomap_flags & IOMAP_DIRECT))

	if (!(iomap_flags & IOMAP_DIRECT) || imap->br_state == XFS_EXT_NORM)

		return 0;

	return xfs_reflink_convert_cow_extent(ip, imap, offset_fsb, count_fsb);

	trace_xfs_reflink_convert_cow(ip, imap);

	return xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);



out_unreserve:

	xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,