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Commit dbcabad1 authored by David Chinner's avatar David Chinner Committed by Tim Shimmin
Browse files

[XFS] Fix block reservation mechanism. 



The block reservation mechanism has been broken since the per-cpu
superblock counters were introduced. Make the block reservation code work
with the per-cpu counters by syncing the counters, snapshotting the amount
of available space and then doing a modifcation of the counter state
according to the result. Continue in a loop until we either have no space
available or we reserve some space.

SGI-PV: 956323
SGI-Modid: xfs-linux-melb:xfs-kern:27895a

Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarTim Shimmin <tes@sgi.com>
parent 20f4ebf2

fs/xfs/xfs_fsops.c

+49 −5
Original line number Diff line number Diff line
@@ -460,7 +460,7 @@ xfs_fs_counts( 
{

	unsigned long	s;



	xfs_icsb_sync_counters_lazy(mp);

	xfs_icsb_sync_counters_flags(mp, XFS_ICSB_LAZY_COUNT);

	s = XFS_SB_LOCK(mp);

	cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);

	cnt->freertx = mp->m_sb.sb_frextents;
@@ -491,7 +491,7 @@ xfs_reserve_blocks( 
	__uint64_t              *inval,

	xfs_fsop_resblks_t      *outval)

{

	__int64_t		lcounter, delta;

	__int64_t		lcounter, delta, fdblks_delta;

	__uint64_t		request;

	unsigned long		s;
@@ -504,17 +504,35 @@ xfs_reserve_blocks( 
	}



	request = *inval;



	/*

	 * With per-cpu counters, this becomes an interesting

	 * problem. we needto work out if we are freeing or allocation

	 * blocks first, then we can do the modification as necessary.

	 *

	 * We do this under the XFS_SB_LOCK so that if we are near

	 * ENOSPC, we will hold out any changes while we work out

	 * what to do. This means that the amount of free space can

	 * change while we do this, so we need to retry if we end up

	 * trying to reserve more space than is available.

	 *

	 * We also use the xfs_mod_incore_sb() interface so that we

	 * don't have to care about whether per cpu counter are

	 * enabled, disabled or even compiled in....

	 */

retry:

	s = XFS_SB_LOCK(mp);

	xfs_icsb_sync_counters_flags(mp, XFS_ICSB_SB_LOCKED);



	/*

	 * If our previous reservation was larger than the current value,

	 * then move any unused blocks back to the free pool.

	 */



	fdblks_delta = 0;

	if (mp->m_resblks > request) {

		lcounter = mp->m_resblks_avail - request;

		if (lcounter  > 0) {		/* release unused blocks */

			mp->m_sb.sb_fdblocks += lcounter;

			fdblks_delta = lcounter;

			mp->m_resblks_avail -= lcounter;

		}

		mp->m_resblks = request;
@@ -522,24 +540,50 @@ xfs_reserve_blocks( 
		__int64_t	free;



		free =  mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);

		if (!free)

			goto out; /* ENOSPC and fdblks_delta = 0 */



		delta = request - mp->m_resblks;

		lcounter = free - delta;

		if (lcounter < 0) {

			/* We can't satisfy the request, just get what we can */

			mp->m_resblks += free;

			mp->m_resblks_avail += free;

			fdblks_delta = -free;

			mp->m_sb.sb_fdblocks = XFS_ALLOC_SET_ASIDE(mp);

		} else {

			fdblks_delta = -delta;

			mp->m_sb.sb_fdblocks =

				lcounter + XFS_ALLOC_SET_ASIDE(mp);

			mp->m_resblks = request;

			mp->m_resblks_avail += delta;

		}

	}



out:

	outval->resblks = mp->m_resblks;

	outval->resblks_avail = mp->m_resblks_avail;

	XFS_SB_UNLOCK(mp, s);



	if (fdblks_delta) {

		/*

		 * If we are putting blocks back here, m_resblks_avail is

		 * already at it's max so this will put it in the free pool.

		 *

		 * If we need space, we'll either succeed in getting it

		 * from the free block count or we'll get an enospc. If

		 * we get a ENOSPC, it means things changed while we were

		 * calculating fdblks_delta and so we should try again to

		 * see if there is anything left to reserve.

		 *

		 * Don't set the reserved flag here - we don't want to reserve

		 * the extra reserve blocks from the reserve.....

		 */

		int error;

		error = xfs_mod_incore_sb(mp, XFS_SBS_FDBLOCKS, fdblks_delta, 0);

		if (error == ENOSPC)

			goto retry;

	}



	return 0;

}

fs/xfs/xfs_mount.c

+3 −13
Original line number Diff line number Diff line
@@ -1979,8 +1979,8 @@ xfs_icsb_enable_counter( 
	xfs_icsb_unlock_all_counters(mp);

}



STATIC void

xfs_icsb_sync_counters_int(

void

xfs_icsb_sync_counters_flags(

	xfs_mount_t	*mp,

	int		flags)

{
@@ -2012,17 +2012,7 @@ STATIC void 
xfs_icsb_sync_counters(

	xfs_mount_t	*mp)

{

	xfs_icsb_sync_counters_int(mp, 0);

}



/*

 * lazy addition used for things like df, background sb syncs, etc

 */

void

xfs_icsb_sync_counters_lazy(

	xfs_mount_t	*mp)

{

	xfs_icsb_sync_counters_int(mp, XFS_ICSB_LAZY_COUNT);

	xfs_icsb_sync_counters_flags(mp, 0);

}



/*

fs/xfs/xfs_mount.h

+1 −1
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ typedef struct xfs_icsb_cnts { 
#define XFS_ICSB_LAZY_COUNT	(1 << 1)	/* accuracy not needed */



extern int	xfs_icsb_init_counters(struct xfs_mount *);

extern void	xfs_icsb_sync_counters_lazy(struct xfs_mount *);

extern void	xfs_icsb_sync_counters_flags(struct xfs_mount *, int);



#else

#define xfs_icsb_init_counters(mp)	(0)

fs/xfs/xfs_vfsops.c

+1 −1
Original line number Diff line number Diff line
@@ -806,7 +806,7 @@ xfs_statvfs( 


	statp->f_type = XFS_SB_MAGIC;



	xfs_icsb_sync_counters_lazy(mp);

	xfs_icsb_sync_counters_flags(mp, XFS_ICSB_LAZY_COUNT);

	s = XFS_SB_LOCK(mp);

	statp->f_bsize = sbp->sb_blocksize;

	lsize = sbp->sb_logstart ? sbp->sb_logblocks : 0;