From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:33126 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854AbcGMQuu (ORCPT ); Wed, 13 Jul 2016 12:50:50 -0400 Date: Wed, 13 Jul 2016 09:50:08 -0700 From: "Darrick J. Wong" To: Brian Foster Cc: david@fromorbit.com, linux-fsdevel@vger.kernel.org, vishal.l.verma@intel.com, Dave Chinner , xfs@oss.sgi.com Subject: Re: [PATCH 031/119] xfs: rmap btree requires more reserved free space Message-ID: <20160713165008.GH13625@birch.djwong.org> References: <146612627129.12839.3827886950949809165.stgit@birch.djwong.org> <146612647122.12839.13018596528662402580.stgit@birch.djwong.org> <20160708132154.GC59278@bfoster.bfoster> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160708132154.GC59278@bfoster.bfoster> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Jul 08, 2016 at 09:21:55AM -0400, Brian Foster wrote: > On Thu, Jun 16, 2016 at 06:21:11PM -0700, Darrick J. Wong wrote: > > From: Dave Chinner > > > > The rmap btree is allocated from the AGFL, which means we have to > > ensure ENOSPC is reported to userspace before we run out of free > > space in each AG. The last allocation in an AG can cause a full > > height rmap btree split, and that means we have to reserve at least > > this many blocks *in each AG* to be placed on the AGFL at ENOSPC. > > Update the various space calculation functiosn to handle this. > > functions > > > > > Also, because the macros are now executing conditional code and are called quite > > frequently, convert them to functions that initialise varaibles in the struct > > xfs_mount, use the new variables everywhere and document the calculations > > better. > > > > v2: If rmapbt is disabled, it is incorrect to require 1 extra AGFL block > > for the rmapbt (due to the + 1); the entire clause needs to be gated > > on the feature flag. > > > > v3: Use m_rmap_maxlevels to determine min_free. > > > > [darrick.wong@oracle.com: don't reserve blocks if !rmap] > > [dchinner@redhat.com: update m_ag_max_usable after growfs] > > > > Signed-off-by: Dave Chinner > > Signed-off-by: Darrick J. Wong > > Reviewed-by: Dave Chinner > > Signed-off-by: Dave Chinner > > --- > > fs/xfs/libxfs/xfs_alloc.c | 71 +++++++++++++++++++++++++++++++++++++++++++++ > > fs/xfs/libxfs/xfs_alloc.h | 41 +++----------------------- > > fs/xfs/libxfs/xfs_bmap.c | 2 + > > fs/xfs/libxfs/xfs_sb.c | 2 + > > fs/xfs/xfs_discard.c | 2 + > > fs/xfs/xfs_fsops.c | 5 ++- > > fs/xfs/xfs_log_recover.c | 1 + > > fs/xfs/xfs_mount.c | 2 + > > fs/xfs/xfs_mount.h | 2 + > > fs/xfs/xfs_super.c | 2 + > > 10 files changed, 88 insertions(+), 42 deletions(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > > index 570ca17..4c8ffd4 100644 > > --- a/fs/xfs/libxfs/xfs_alloc.c > > +++ b/fs/xfs/libxfs/xfs_alloc.c > > @@ -63,6 +63,72 @@ xfs_prealloc_blocks( > > } > > > > /* > > + * In order to avoid ENOSPC-related deadlock caused by out-of-order locking of > > + * AGF buffer (PV 947395), we place constraints on the relationship among > > + * actual allocations for data blocks, freelist blocks, and potential file data > > + * bmap btree blocks. However, these restrictions may result in no actual space > > + * allocated for a delayed extent, for example, a data block in a certain AG is > > + * allocated but there is no additional block for the additional bmap btree > > + * block due to a split of the bmap btree of the file. The result of this may > > + * lead to an infinite loop when the file gets flushed to disk and all delayed > > + * extents need to be actually allocated. To get around this, we explicitly set > > + * aside a few blocks which will not be reserved in delayed allocation. > > + * > > + * The minimum number of needed freelist blocks is 4 fsbs _per AG_ when we are > > + * not using rmap btrees a potential split of file's bmap btree requires 1 fsb, > > + * so we set the number of set-aside blocks to 4 + 4*agcount when not using > > + * rmap btrees. > > + * > > That's a bit wordy. Yikes, that whole thing is a single sentence! One thing I'm not really sure about is how "a potential split of file's bmap btree requires 1 fsb" seems to translate to 4 in the actual formula. I'd have thought it would be m_bm_maxlevels or something... not just 4. /* * When rmap is disabled, we need to reserve 4 fsbs _per AG_ for the freelist * and 4 more to handle a potential split of the file's bmap btree. * * When rmap is enabled, we must also be able to handle two rmap btree inserts * to record both the file data extent and a new bmbt block. The bmbt block * might not be in the same AG as the file data extent. In the worst case * the bmap btree splits multiple levels and all the new blocks come from * different AGs, so set aside enough to handle rmap btree splits in all AGs. */ > > + * When rmap btrees are active, we have to consider that using the last block > > + * in the AG can cause a full height rmap btree split and we need enough blocks > > + * on the AGFL to be able to handle this. That means we have, in addition to > > + * the above consideration, another (2 * mp->m_rmap_levels) - 1 blocks required > > + * to be available to the free list. > > I'm probably missing something, but why does a full tree split require 2 > blocks per-level (minus 1)? Wouldn't that involve an allocated block per > level (and possibly a new root block)? The whole rmap clause is wrong. :( I think we'll be fine with agcount * m_rmap_maxlevels. > Otherwise, the rest looks good to me. Cool. > Brian > > > + */ > > +unsigned int > > +xfs_alloc_set_aside( > > + struct xfs_mount *mp) > > +{ > > + unsigned int blocks; > > + > > + blocks = 4 + (mp->m_sb.sb_agcount * XFS_ALLOC_AGFL_RESERVE); > > + if (!xfs_sb_version_hasrmapbt(&mp->m_sb)) > > + return blocks; > > + return blocks + (mp->m_sb.sb_agcount * (2 * mp->m_rmap_maxlevels) - 1); > > +} > > + > > +/* > > + * When deciding how much space to allocate out of an AG, we limit the > > + * allocation maximum size to the size the AG. However, we cannot use all the > > + * blocks in the AG - some are permanently used by metadata. These > > + * blocks are generally: > > + * - the AG superblock, AGF, AGI and AGFL > > + * - the AGF (bno and cnt) and AGI btree root blocks, and optionally > > + * the AGI free inode and rmap btree root blocks. > > + * - blocks on the AGFL according to xfs_alloc_set_aside() limits > > + * > > + * The AG headers are sector sized, so the amount of space they take up is > > + * dependent on filesystem geometry. The others are all single blocks. > > + */ > > +unsigned int > > +xfs_alloc_ag_max_usable(struct xfs_mount *mp) > > +{ > > + unsigned int blocks; > > + > > + blocks = XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)); /* ag headers */ > > + blocks += XFS_ALLOC_AGFL_RESERVE; > > + blocks += 3; /* AGF, AGI btree root blocks */ > > + if (xfs_sb_version_hasfinobt(&mp->m_sb)) > > + blocks++; /* finobt root block */ > > + if (xfs_sb_version_hasrmapbt(&mp->m_sb)) { > > + /* rmap root block + full tree split on full AG */ > > + blocks += 1 + (2 * mp->m_ag_maxlevels) - 1; I think this could be blocks++ since we now have AG reservations. --D > > + } > > + > > + return mp->m_sb.sb_agblocks - blocks; > > +} > > + > > +/* > > * Lookup the record equal to [bno, len] in the btree given by cur. > > */ > > STATIC int /* error */ > > @@ -1904,6 +1970,11 @@ xfs_alloc_min_freelist( > > /* space needed by-size freespace btree */ > > min_free += min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_CNTi] + 1, > > mp->m_ag_maxlevels); > > + /* space needed reverse mapping used space btree */ > > + if (xfs_sb_version_hasrmapbt(&mp->m_sb)) > > + min_free += min_t(unsigned int, > > + pag->pagf_levels[XFS_BTNUM_RMAPi] + 1, > > + mp->m_rmap_maxlevels); > > > > return min_free; > > } > > diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h > > index 0721a48..7b6c66b 100644 > > --- a/fs/xfs/libxfs/xfs_alloc.h > > +++ b/fs/xfs/libxfs/xfs_alloc.h > > @@ -56,42 +56,6 @@ typedef unsigned int xfs_alloctype_t; > > #define XFS_ALLOC_FLAG_FREEING 0x00000002 /* indicate caller is freeing extents*/ > > > > /* > > - * In order to avoid ENOSPC-related deadlock caused by > > - * out-of-order locking of AGF buffer (PV 947395), we place > > - * constraints on the relationship among actual allocations for > > - * data blocks, freelist blocks, and potential file data bmap > > - * btree blocks. However, these restrictions may result in no > > - * actual space allocated for a delayed extent, for example, a data > > - * block in a certain AG is allocated but there is no additional > > - * block for the additional bmap btree block due to a split of the > > - * bmap btree of the file. The result of this may lead to an > > - * infinite loop in xfssyncd when the file gets flushed to disk and > > - * all delayed extents need to be actually allocated. To get around > > - * this, we explicitly set aside a few blocks which will not be > > - * reserved in delayed allocation. Considering the minimum number of > > - * needed freelist blocks is 4 fsbs _per AG_, a potential split of file's bmap > > - * btree requires 1 fsb, so we set the number of set-aside blocks > > - * to 4 + 4*agcount. > > - */ > > -#define XFS_ALLOC_SET_ASIDE(mp) (4 + ((mp)->m_sb.sb_agcount * 4)) > > - > > -/* > > - * When deciding how much space to allocate out of an AG, we limit the > > - * allocation maximum size to the size the AG. However, we cannot use all the > > - * blocks in the AG - some are permanently used by metadata. These > > - * blocks are generally: > > - * - the AG superblock, AGF, AGI and AGFL > > - * - the AGF (bno and cnt) and AGI btree root blocks > > - * - 4 blocks on the AGFL according to XFS_ALLOC_SET_ASIDE() limits > > - * > > - * The AG headers are sector sized, so the amount of space they take up is > > - * dependent on filesystem geometry. The others are all single blocks. > > - */ > > -#define XFS_ALLOC_AG_MAX_USABLE(mp) \ > > - ((mp)->m_sb.sb_agblocks - XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)) - 7) > > - > > - > > -/* > > * Argument structure for xfs_alloc routines. > > * This is turned into a structure to avoid having 20 arguments passed > > * down several levels of the stack. > > @@ -133,6 +97,11 @@ typedef struct xfs_alloc_arg { > > #define XFS_ALLOC_INITIAL_USER_DATA (1 << 1)/* special case start of file */ > > #define XFS_ALLOC_USERDATA_ZERO (1 << 2)/* zero extent on allocation */ > > > > +/* freespace limit calculations */ > > +#define XFS_ALLOC_AGFL_RESERVE 4 > > +unsigned int xfs_alloc_set_aside(struct xfs_mount *mp); > > +unsigned int xfs_alloc_ag_max_usable(struct xfs_mount *mp); > > + > > xfs_extlen_t xfs_alloc_longest_free_extent(struct xfs_mount *mp, > > struct xfs_perag *pag, xfs_extlen_t need); > > unsigned int xfs_alloc_min_freelist(struct xfs_mount *mp, > > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c > > index 2c28f2a..61c0231 100644 > > --- a/fs/xfs/libxfs/xfs_bmap.c > > +++ b/fs/xfs/libxfs/xfs_bmap.c > > @@ -3672,7 +3672,7 @@ xfs_bmap_btalloc( > > args.fsbno = ap->blkno; > > > > /* Trim the allocation back to the maximum an AG can fit. */ > > - args.maxlen = MIN(ap->length, XFS_ALLOC_AG_MAX_USABLE(mp)); > > + args.maxlen = MIN(ap->length, mp->m_ag_max_usable); > > args.firstblock = *ap->firstblock; > > blen = 0; > > if (nullfb) { > > diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c > > index f86226b..59c9f59 100644 > > --- a/fs/xfs/libxfs/xfs_sb.c > > +++ b/fs/xfs/libxfs/xfs_sb.c > > @@ -749,6 +749,8 @@ xfs_sb_mount_common( > > mp->m_ialloc_min_blks = sbp->sb_spino_align; > > else > > mp->m_ialloc_min_blks = mp->m_ialloc_blks; > > + mp->m_alloc_set_aside = xfs_alloc_set_aside(mp); > > + mp->m_ag_max_usable = xfs_alloc_ag_max_usable(mp); > > } > > > > /* > > diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c > > index 272c3f8..4ff499a 100644 > > --- a/fs/xfs/xfs_discard.c > > +++ b/fs/xfs/xfs_discard.c > > @@ -179,7 +179,7 @@ xfs_ioc_trim( > > * matter as trimming blocks is an advisory interface. > > */ > > if (range.start >= XFS_FSB_TO_B(mp, mp->m_sb.sb_dblocks) || > > - range.minlen > XFS_FSB_TO_B(mp, XFS_ALLOC_AG_MAX_USABLE(mp)) || > > + range.minlen > XFS_FSB_TO_B(mp, mp->m_ag_max_usable) || > > range.len < mp->m_sb.sb_blocksize) > > return -EINVAL; > > > > diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c > > index 8a85e49..3772f6c 100644 > > --- a/fs/xfs/xfs_fsops.c > > +++ b/fs/xfs/xfs_fsops.c > > @@ -583,6 +583,7 @@ xfs_growfs_data_private( > > } else > > mp->m_maxicount = 0; > > xfs_set_low_space_thresholds(mp); > > + mp->m_alloc_set_aside = xfs_alloc_set_aside(mp); > > > > /* update secondary superblocks. */ > > for (agno = 1; agno < nagcount; agno++) { > > @@ -720,7 +721,7 @@ xfs_fs_counts( > > cnt->allocino = percpu_counter_read_positive(&mp->m_icount); > > cnt->freeino = percpu_counter_read_positive(&mp->m_ifree); > > cnt->freedata = percpu_counter_read_positive(&mp->m_fdblocks) - > > - XFS_ALLOC_SET_ASIDE(mp); > > + mp->m_alloc_set_aside; > > > > spin_lock(&mp->m_sb_lock); > > cnt->freertx = mp->m_sb.sb_frextents; > > @@ -793,7 +794,7 @@ retry: > > __int64_t free; > > > > free = percpu_counter_sum(&mp->m_fdblocks) - > > - XFS_ALLOC_SET_ASIDE(mp); > > + mp->m_alloc_set_aside; > > if (!free) > > goto out; /* ENOSPC and fdblks_delta = 0 */ > > > > diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c > > index 0c41bd2..b33187b 100644 > > --- a/fs/xfs/xfs_log_recover.c > > +++ b/fs/xfs/xfs_log_recover.c > > @@ -5027,6 +5027,7 @@ xlog_do_recover( > > xfs_warn(mp, "Failed post-recovery per-ag init: %d", error); > > return error; > > } > > + mp->m_alloc_set_aside = xfs_alloc_set_aside(mp); > > > > xlog_recover_check_summary(log); > > > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c > > index 8af1c88..879f3ef 100644 > > --- a/fs/xfs/xfs_mount.c > > +++ b/fs/xfs/xfs_mount.c > > @@ -1219,7 +1219,7 @@ xfs_mod_fdblocks( > > batch = XFS_FDBLOCKS_BATCH; > > > > __percpu_counter_add(&mp->m_fdblocks, delta, batch); > > - if (__percpu_counter_compare(&mp->m_fdblocks, XFS_ALLOC_SET_ASIDE(mp), > > + if (__percpu_counter_compare(&mp->m_fdblocks, mp->m_alloc_set_aside, > > XFS_FDBLOCKS_BATCH) >= 0) { > > /* we had space! */ > > return 0; > > diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h > > index 0ed0f29..b36676c 100644 > > --- a/fs/xfs/xfs_mount.h > > +++ b/fs/xfs/xfs_mount.h > > @@ -123,6 +123,8 @@ typedef struct xfs_mount { > > uint m_in_maxlevels; /* max inobt btree levels. */ > > uint m_rmap_maxlevels; /* max rmap btree levels */ > > xfs_extlen_t m_ag_prealloc_blocks; /* reserved ag blocks */ > > + uint m_alloc_set_aside; /* space we can't use */ > > + uint m_ag_max_usable; /* max space per AG */ > > struct radix_tree_root m_perag_tree; /* per-ag accounting info */ > > spinlock_t m_perag_lock; /* lock for m_perag_tree */ > > struct mutex m_growlock; /* growfs mutex */ > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > > index bf63f6d..1575849 100644 > > --- a/fs/xfs/xfs_super.c > > +++ b/fs/xfs/xfs_super.c > > @@ -1076,7 +1076,7 @@ xfs_fs_statfs( > > statp->f_blocks = sbp->sb_dblocks - lsize; > > spin_unlock(&mp->m_sb_lock); > > > > - statp->f_bfree = fdblocks - XFS_ALLOC_SET_ASIDE(mp); > > + statp->f_bfree = fdblocks - mp->m_alloc_set_aside; > > statp->f_bavail = statp->f_bfree; > > > > fakeinos = statp->f_bfree << sbp->sb_inopblog; > > > > _______________________________________________ > > xfs mailing list > > xfs@oss.sgi.com > > http://oss.sgi.com/mailman/listinfo/xfs