From dbcabad19aa91dc9bc7176fd2853fa74f724cd2f Mon Sep 17 00:00:00 2001 From: David Chinner Date: Sat, 10 Feb 2007 18:36:17 +1100 Subject: [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: David Chinner Signed-off-by: Christoph Hellwig Signed-off-by: Tim Shimmin --- fs/xfs/xfs_fsops.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 49 insertions(+), 5 deletions(-) (limited to 'fs/xfs/xfs_fsops.c') diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c index c064e72..bfde9e6 100644 --- a/fs/xfs/xfs_fsops.c +++ b/fs/xfs/xfs_fsops.c @@ -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; } -- cgit v1.1