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Commit 2ba090d5 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
Browse files

xfs: use WRITE_ONCE to update if_seq 



This adds ordering of the updates and makes sure we always see the if_seq
update before the extent tree is modified.

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 a0e336ba

fs/xfs/libxfs/xfs_iext_tree.c

+17 −3
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include "xfs_inode_fork.h"

#include "xfs_trans_resv.h"

#include "xfs_mount.h"

#include "xfs_bmap.h"

#include "xfs_trace.h"



/*
@@ -612,6 +613,19 @@ xfs_iext_realloc_root( 
	cur->leaf = new;

}



/*

 * Increment the sequence counter if we are on a COW fork.  This allows

 * the writeback code to skip looking for a COW extent if the COW fork

 * hasn't changed.  We use WRITE_ONCE here to ensure the update to the

 * sequence counter is seen before the modifications to the extent

 * tree itself take effect.

 */

static inline void xfs_iext_inc_seq(struct xfs_ifork *ifp, int state)

{

	if (state & BMAP_COWFORK)

		WRITE_ONCE(ifp->if_seq, READ_ONCE(ifp->if_seq) + 1);

}



void

xfs_iext_insert(

	struct xfs_inode	*ip,
@@ -624,7 +638,7 @@ xfs_iext_insert( 
	struct xfs_iext_leaf	*new = NULL;

	int			nr_entries, i;



	ifp->if_seq++;

	xfs_iext_inc_seq(ifp, state);



	if (ifp->if_height == 0)

		xfs_iext_alloc_root(ifp, cur);
@@ -866,7 +880,7 @@ xfs_iext_remove( 
	ASSERT(ifp->if_u1.if_root != NULL);

	ASSERT(xfs_iext_valid(ifp, cur));



	ifp->if_seq++;

	xfs_iext_inc_seq(ifp, state);



	nr_entries = xfs_iext_leaf_nr_entries(ifp, leaf, cur->pos) - 1;

	for (i = cur->pos; i < nr_entries; i++)
@@ -974,7 +988,7 @@ xfs_iext_update_extent( 
{

	struct xfs_ifork	*ifp = xfs_iext_state_to_fork(ip, state);



	ifp->if_seq++;

	xfs_iext_inc_seq(ifp, state);



	if (cur->pos == 0) {

		struct xfs_bmbt_irec	old;

fs/xfs/xfs_aops.c

+2 −2
Original line number Diff line number Diff line
@@ -351,7 +351,7 @@ xfs_map_blocks( 
	if (imap_valid &&

	    (!xfs_inode_has_cow_data(ip) ||

	     wpc->io_type == XFS_IO_COW ||

	     wpc->cow_seq == ip->i_cowfp->if_seq))

	     wpc->cow_seq == READ_ONCE(ip->i_cowfp->if_seq)))

		return 0;



	if (XFS_FORCED_SHUTDOWN(mp))
@@ -380,7 +380,7 @@ xfs_map_blocks( 
	    xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap))

		cow_fsb = imap.br_startoff;

	if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {

		wpc->cow_seq = ip->i_cowfp->if_seq;

		wpc->cow_seq = READ_ONCE(ip->i_cowfp->if_seq);

		xfs_iunlock(ip, XFS_ILOCK_SHARED);

		/*

		 * Truncate can race with writeback since writeback doesn't

fs/xfs/xfs_iomap.c

+2 −1
Original line number Diff line number Diff line
@@ -655,6 +655,7 @@ xfs_iomap_write_allocate( 
	unsigned int	*cow_seq)

{

	xfs_mount_t	*mp = ip->i_mount;

	struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);

	xfs_fileoff_t	offset_fsb, last_block;

	xfs_fileoff_t	end_fsb, map_start_fsb;

	xfs_filblks_t	count_fsb;
@@ -768,7 +769,7 @@ xfs_iomap_write_allocate( 
				goto error0;



			if (whichfork == XFS_COW_FORK)

				*cow_seq = XFS_IFORK_PTR(ip, whichfork)->if_seq;

				*cow_seq = READ_ONCE(ifp->if_seq);

			xfs_iunlock(ip, XFS_ILOCK_EXCL);

		}