Re: [PATCH 14/15] xfs: compute absolute maximum nlevels for each btree type
From: Dave Chinner <david@fromorbit.com>
Date: 2021-10-13 07:57:47
On Tue, Oct 12, 2021 at 04:33:50PM -0700, Darrick J. Wong wrote:
quoted hunk ↗ jump to hunk
From: Darrick J. Wong <djwong@kernel.org> Add code for all five btree types so that we can compute the absolute maximum possible btree height for each btree type. This is a setup for the next patch, which makes every btree type have its own cursor cache. The functions are exported so that we can have xfs_db report the absolute maximum btree heights for each btree type, rather than making everyone run their own ad-hoc computations. Signed-off-by: Darrick J. Wong <djwong@kernel.org> --- fs/xfs/libxfs/xfs_alloc.c | 1 + fs/xfs/libxfs/xfs_alloc_btree.c | 13 +++++++++++ fs/xfs/libxfs/xfs_alloc_btree.h | 2 ++ fs/xfs/libxfs/xfs_bmap.c | 1 + fs/xfs/libxfs/xfs_bmap_btree.c | 14 ++++++++++++ fs/xfs/libxfs/xfs_bmap_btree.h | 2 ++ fs/xfs/libxfs/xfs_btree.c | 41 ++++++++++++++++++++++++++++++++++++ fs/xfs/libxfs/xfs_btree.h | 3 +++ fs/xfs/libxfs/xfs_fs.h | 2 ++ fs/xfs/libxfs/xfs_ialloc.c | 1 + fs/xfs/libxfs/xfs_ialloc_btree.c | 19 +++++++++++++++++ fs/xfs/libxfs/xfs_ialloc_btree.h | 2 ++ fs/xfs/libxfs/xfs_refcount_btree.c | 20 ++++++++++++++++++ fs/xfs/libxfs/xfs_refcount_btree.h | 2 ++ fs/xfs/libxfs/xfs_rmap_btree.c | 27 ++++++++++++++++++++++++ fs/xfs/libxfs/xfs_rmap_btree.h | 2 ++ 16 files changed, 152 insertions(+)diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 55c5adc9b54e..7145416a230c 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c@@ -2198,6 +2198,7 @@ xfs_alloc_compute_maxlevels( { mp->m_ag_maxlevels = xfs_btree_compute_maxlevels(mp->m_alloc_mnr, (mp->m_sb.sb_agblocks + 1) / 2); + ASSERT(mp->m_ag_maxlevels <= xfs_allocbt_absolute_maxlevels()); } /*diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c index f14bad21503f..61f6d266b822 100644 --- a/fs/xfs/libxfs/xfs_alloc_btree.c +++ b/fs/xfs/libxfs/xfs_alloc_btree.c@@ -582,6 +582,19 @@ xfs_allocbt_maxrecs( return blocklen / (sizeof(xfs_alloc_key_t) + sizeof(xfs_alloc_ptr_t)); } +/* Compute the max possible height of the maximally sized free space btree. */ +unsigned int +xfs_allocbt_absolute_maxlevels(void) +{ + unsigned int minrecs[2]; + + xfs_btree_absolute_minrecs(minrecs, 0, sizeof(xfs_alloc_rec_t), + sizeof(xfs_alloc_key_t) + sizeof(xfs_alloc_ptr_t)); + + return xfs_btree_compute_maxlevels(minrecs, + (XFS_MAX_AG_BLOCKS + 1) / 2); +}
Hmmmm. This is kinds messy. I'd prefer we share code with the
xfs_allocbt_maxrecs() function that do this. Not sure "absolute" is
the right word, either. It's more a function of the on-disk format
maximum, not an "absolute" thing.
I mean, we know that the worst case is going to be for each btree
type - we don't need to pass in XFS_BTREE_CRC_BLOCKS or
XFS_BTREE_LONG_PTRS to generic code for it to branch multiple times
to be generic. Instead:
static inline int
xfs_allocbt_block_maxrecs(
int blocklen,
int leaf)
{
if (leaf)
return blocklen / sizeof(xfs_alloc_rec_t);
return blocklen / (sizeof(xfs_alloc_key_t) + sizeof(xfs_alloc_ptr_t));
}
/*
* Calculate number of records in an alloc btree block.
*/
int
xfs_allocbt_maxrecs(
struct xfs_mount *mp,
int blocklen,
int leaf)
{
blocklen -= XFS_ALLOC_BLOCK_LEN(mp);
return xfs_allobt_block_maxrecs(blocklen, leaf);
}
xfs_allocbt_maxlevels_ondisk()
{
unsigned int minrecs[2];
minrecs[0] = xfs_allocbt_block_maxrecs(
XFS_MIN_BLOCKSIZE - XFS_BTREE_SBLOCK_LEN, true) / 2;
minrecs[1] = xfs_allocbt_block_maxrecs(
XFS_MIN_BLOCKSIZE - XFS_BTREE_SBLOCK_LEN, false) / 2;
return xfs_btree_compute_maxlevels(minrecs,
(XFS_MAX_AG_BLOCKS + 1) / 2);
}
All the other btree implementations factor this way, too, allowing
the minrec values to be calculated clearly and directly in the
specific btree function...
quoted hunk ↗ jump to hunk
+ /* Calculate the freespace btree size for some records. */ xfs_extlen_t xfs_allocbt_calc_size(diff --git a/fs/xfs/libxfs/xfs_alloc_btree.h b/fs/xfs/libxfs/xfs_alloc_btree.h index 2f6b816aaf9f..c47d0e285435 100644 --- a/fs/xfs/libxfs/xfs_alloc_btree.h +++ b/fs/xfs/libxfs/xfs_alloc_btree.h@@ -60,4 +60,6 @@ extern xfs_extlen_t xfs_allocbt_calc_size(struct xfs_mount *mp, void xfs_allocbt_commit_staged_btree(struct xfs_btree_cur *cur, struct xfs_trans *tp, struct xfs_buf *agbp); +unsigned int xfs_allocbt_absolute_maxlevels(void); + #endif /* __XFS_ALLOC_BTREE_H__ */diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index 2ae5bf9a74e7..7e70df8d1a9b 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c@@ -93,6 +93,7 @@ xfs_bmap_compute_maxlevels( maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs; } mp->m_bm_maxlevels[whichfork] = level; + ASSERT(mp->m_bm_maxlevels[whichfork] <= xfs_bmbt_absolute_maxlevels()); } unsigned intdiff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c index b90122de0df0..7001aff639d2 100644 --- a/fs/xfs/libxfs/xfs_bmap_btree.c +++ b/fs/xfs/libxfs/xfs_bmap_btree.c@@ -587,6 +587,20 @@ xfs_bmbt_maxrecs( return blocklen / (sizeof(xfs_bmbt_key_t) + sizeof(xfs_bmbt_ptr_t)); } +/* Compute the max possible height of the maximally sized bmap btree. */ +unsigned int +xfs_bmbt_absolute_maxlevels(void) +{ + unsigned int minrecs[2]; + + xfs_btree_absolute_minrecs(minrecs, XFS_BTREE_LONG_PTRS, + sizeof(struct xfs_bmbt_rec), + sizeof(struct xfs_bmbt_key) + + sizeof(xfs_bmbt_ptr_t)); + + return xfs_btree_compute_maxlevels(minrecs, MAXEXTNUM) + 1; +}
minrecs[0] = xfs_bmbt_block_maxrecs( XFS_MIN_BLOCKSIZE - XFS_BTREE_LBLOCK_LEN, true) / 2; ....
quoted hunk ↗ jump to hunk
+ /* * Calculate number of records in a bmap btree inode root. */diff --git a/fs/xfs/libxfs/xfs_bmap_btree.h b/fs/xfs/libxfs/xfs_bmap_btree.h index 729e3bc569be..e9218e92526b 100644 --- a/fs/xfs/libxfs/xfs_bmap_btree.h +++ b/fs/xfs/libxfs/xfs_bmap_btree.h@@ -110,4 +110,6 @@ extern struct xfs_btree_cur *xfs_bmbt_init_cursor(struct xfs_mount *, extern unsigned long long xfs_bmbt_calc_size(struct xfs_mount *mp, unsigned long long len); +unsigned int xfs_bmbt_absolute_maxlevels(void); + #endif /* __XFS_BMAP_BTREE_H__ */diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c index b95c817ad90d..bea1bdf9b8b9 100644 --- a/fs/xfs/libxfs/xfs_btree.c +++ b/fs/xfs/libxfs/xfs_btree.c@@ -4964,3 +4964,44 @@ xfs_btree_has_more_records( else return block->bb_u.s.bb_rightsib != cpu_to_be32(NULLAGBLOCK); } + +/* + * Compute absolute minrecs for leaf and node btree blocks. Callers should set + * BTREE_LONG_PTRS and BTREE_OVERLAPPING as they would for regular cursors. + * Set BTREE_CRC_BLOCKS if the btree type is supported /only/ on V5 or newer + * filesystems. + */ +void +xfs_btree_absolute_minrecs( + unsigned int *minrecs, + unsigned int bc_flags, + unsigned int leaf_recbytes, + unsigned int node_recbytes) +{ + unsigned int min_recbytes; + + /* + * If this btree type is supported on V4, we use the smaller V4 min + * block size along with the V4 header size. If the btree type is only + * supported on V5, use the (twice as large) V5 min block size along + * with the V5 header size. + */ + if (!(bc_flags & XFS_BTREE_CRC_BLOCKS)) { + if (bc_flags & XFS_BTREE_LONG_PTRS) + min_recbytes = XFS_MIN_BLOCKSIZE - + XFS_BTREE_LBLOCK_LEN; + else + min_recbytes = XFS_MIN_BLOCKSIZE - + XFS_BTREE_SBLOCK_LEN; + } else if (bc_flags & XFS_BTREE_LONG_PTRS) { + min_recbytes = XFS_MIN_CRC_BLOCKSIZE - XFS_BTREE_LBLOCK_CRC_LEN; + } else { + min_recbytes = XFS_MIN_CRC_BLOCKSIZE - XFS_BTREE_SBLOCK_CRC_LEN; + } + + if (bc_flags & XFS_BTREE_OVERLAPPING) + node_recbytes <<= 1; + + minrecs[0] = min_recbytes / (2 * leaf_recbytes); + minrecs[1] = min_recbytes / (2 * node_recbytes); +}
This can go away.
quoted hunk ↗ jump to hunk
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h index 20a2828c11ef..acb202839afd 100644 --- a/fs/xfs/libxfs/xfs_btree.h +++ b/fs/xfs/libxfs/xfs_btree.h@@ -601,4 +601,7 @@ xfs_btree_alloc_cursor( return cur; } +void xfs_btree_absolute_minrecs(unsigned int *minrecs, unsigned int bc_flags, + unsigned int leaf_recbytes, unsigned int node_recbytes); + #endif /* __XFS_BTREE_H__ */diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h index bde2b4c64dbe..c43877c8a279 100644 --- a/fs/xfs/libxfs/xfs_fs.h +++ b/fs/xfs/libxfs/xfs_fs.h@@ -268,6 +268,8 @@ typedef struct xfs_fsop_resblks { */ #define XFS_MIN_AG_BYTES (1ULL << 24) /* 16 MB */ #define XFS_MAX_AG_BYTES (1ULL << 40) /* 1 TB */ +#define XFS_MAX_AG_BLOCKS (XFS_MAX_AG_BYTES / XFS_MIN_BLOCKSIZE) +#define XFS_MAX_CRC_AG_BLOCKS (XFS_MAX_AG_BYTES / XFS_MIN_CRC_BLOCKSIZE) /* keep the maximum size under 2^31 by a small amount */ #define XFS_MAX_LOG_BYTES \diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c index 994ad783d407..017aebdda42f 100644 --- a/fs/xfs/libxfs/xfs_ialloc.c +++ b/fs/xfs/libxfs/xfs_ialloc.c@@ -2793,6 +2793,7 @@ xfs_ialloc_setup_geometry( inodes = (1LL << XFS_INO_AGINO_BITS(mp)) >> XFS_INODES_PER_CHUNK_LOG; igeo->inobt_maxlevels = xfs_btree_compute_maxlevels(igeo->inobt_mnr, inodes); + ASSERT(igeo->inobt_maxlevels <= xfs_inobt_absolute_maxlevels()); /* * Set the maximum inode count for this filesystem, being careful notdiff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c index 3a5a24648b87..2e3dd1d798bd 100644 --- a/fs/xfs/libxfs/xfs_ialloc_btree.c +++ b/fs/xfs/libxfs/xfs_ialloc_btree.c@@ -542,6 +542,25 @@ xfs_inobt_maxrecs( return blocklen / (sizeof(xfs_inobt_key_t) + sizeof(xfs_inobt_ptr_t)); } +/* Compute the max possible height of the maximally sized inode btree. */ +unsigned int +xfs_inobt_absolute_maxlevels(void) +{ + unsigned int minrecs[2]; + unsigned long long max_ag_inodes; + + /* + * For the absolute maximum, pretend that we can fill an entire AG + * completely full of inodes except for the AG headers. + */ + max_ag_inodes = (XFS_MAX_AG_BYTES - (4 * BBSIZE)) / XFS_DINODE_MIN_SIZE; + + xfs_btree_absolute_minrecs(minrecs, 0, sizeof(xfs_inobt_rec_t), + sizeof(xfs_inobt_key_t) + sizeof(xfs_inobt_ptr_t)); + + return xfs_btree_compute_maxlevels(minrecs, max_ag_inodes); +}
We've got two different inobt max levels on disk. The inobt which has v4 limits, whilst the finobt that has v5 limits...
+/* Compute the max possible height of the maximally sized rmap btree. */
+unsigned int
+xfs_rmapbt_absolute_maxlevels(void)
+{
+ unsigned int minrecs[2];
+
+ xfs_btree_absolute_minrecs(minrecs,
+ XFS_BTREE_CRC_BLOCKS | XFS_BTREE_OVERLAPPING,
+ sizeof(struct xfs_rmap_rec),
+ sizeof(struct xfs_rmap_key) + sizeof(xfs_rmap_ptr_t));
+
+ /*
+ * Compute the asymptotic maxlevels for an rmapbt on any reflink fs.
+ *
+ * On a reflink filesystem, each AG block can have up to 2^32 (per the
+ * refcount record format) owners, which means that theoretically we
+ * could face up to 2^64 rmap records. However, we're likely to run
+ * out of blocks in the AG long before that happens, which means that
+ * we must compute the max height based on what the btree will look
+ * like if it consumes almost all the blocks in the AG due to maximal
+ * sharing factor.
+ */
+ return xfs_btree_compute_maxlevels_size(XFS_MAX_CRC_AG_BLOCKS,Huh. I don't know where XFS_MAX_CRC_AG_BLOCKS is defined. I must have missed it somewhere? Cheers, Dave. -- Dave Chinner david@fromorbit.com