Message-Id: <1208868379-17580-3-git-send-email-tytso@mit.edu>
Date:	Tue, 22 Apr 2008 08:46:19 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	linux-ext4@...r.kernel.org
Cc:	Theodore Ts'o <tytso@....edu>, "Jose R. Santos" <jrs@...ibm.com>,
	Valerie Clement <valerie.clement@...l.net>
Subject: [E2FSPROGS, RFC] mke2fs: New bitmap and inode table allocation for FLEX_BG

Change the way we allocate bitmaps and inode tables if the FLEX_BG
feature is used at mke2fs time.  It places calculates a new offset for
bitmaps and inode table base on the number of groups that the user
wishes to pack together using the new "-G" option.  Creating a
filesystem with 64 block groups in a flex group can be done by:

mke2fs -j -I 256 -O flex_bg -G 32 /dev/sdX

Signed-off-by: Jose R. Santos <jrs@...ibm.com>
Signed-off-by: Valerie Clement <valerie.clement@...l.net>
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 lib/ext2fs/alloc_tables.c |  118 +++++++++++++++++++++++++++++++++++++++++++-
 lib/ext2fs/initialize.c   |    7 +++
 misc/mke2fs.8.in          |   16 ++++++
 misc/mke2fs.c             |   35 ++++++++++++-
 misc/mke2fs.conf.5.in     |    7 +++
 5 files changed, 177 insertions(+), 6 deletions(-)

diff --git a/lib/ext2fs/alloc_tables.c b/lib/ext2fs/alloc_tables.c
index 9b4f0e5..d87585b 100644
--- a/lib/ext2fs/alloc_tables.c
+++ b/lib/ext2fs/alloc_tables.c
@@ -27,18 +27,80 @@
 #include "ext2_fs.h"
 #include "ext2fs.h"
 
+/*
+ * This routine searches for free blocks that can allocate a full
+ * group of bitmaps or inode tables for a flexbg group.  Returns the
+ * block number with a correct offset were the bitmaps and inode
+ * tables can be allocated continously and in order.
+ */
+static blk_t flexbg_offset(ext2_filsys fs, dgrp_t group, blk_t start_blk,
+			   ext2fs_block_bitmap bmap, int offset, int size)
+{
+	int		flexbg, flexbg_size, elem_size;
+	blk_t		last_blk, first_free = 0;
+	dgrp_t	       	last_grp;
+
+	flexbg_size = 1 << fs->super->s_log_groups_per_flex;
+	flexbg = group / flexbg_size;
+
+	if (size > fs->super->s_blocks_per_group / 8)
+		size = fs->super->s_blocks_per_group / 8;
+
+	/*
+	 * Dont do a long search if the previous block
+	 * search is still valid.
+	 */
+	if (start_blk && group % flexbg_size) {
+		if (size > flexbg_size)
+			elem_size = fs->inode_blocks_per_group;
+		else
+			elem_size = 1;
+		if (ext2fs_test_block_bitmap_range(bmap, start_blk + elem_size,
+						   size))
+			return start_blk + elem_size;
+	}
+
+	start_blk = ext2fs_group_first_block(fs, flexbg_size * flexbg);
+	last_grp = group | (flexbg_size - 1);
+	if (last_grp > fs->group_desc_count)
+		last_grp = fs->group_desc_count;
+	last_blk = ext2fs_group_last_block(fs, last_grp);
+
+	/* Find the first available block */
+	if (ext2fs_get_free_blocks(fs, start_blk, last_blk, 1, bmap,
+				   &first_free))
+		return first_free;
+
+	if (ext2fs_get_free_blocks(fs, first_free + offset, last_blk, size,
+				   bmap, &first_free))
+		return first_free;
+
+	return first_free;
+}
+
 errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 				      ext2fs_block_bitmap bmap)
 {
 	errcode_t	retval;
 	blk_t		group_blk, start_blk, last_blk, new_blk, blk;
-	int		j;
+	dgrp_t		last_grp;
+	int		j, rem_grps, flexbg_size = 0;
 
 	group_blk = ext2fs_group_first_block(fs, group);
 	last_blk = ext2fs_group_last_block(fs, group);
 
 	if (!bmap)
 		bmap = fs->block_map;
+
+	if (EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				      EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
+	    fs->super->s_log_groups_per_flex) {
+		flexbg_size = 1 << fs->super->s_log_groups_per_flex;
+		last_grp = group | (flexbg_size - 1);
+		rem_grps = last_grp - group;
+		if (last_grp > fs->group_desc_count)
+			last_grp = fs->group_desc_count;
+	}
 	
 	/*
 	 * Allocate the block and inode bitmaps, if necessary
@@ -56,6 +118,15 @@ errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 	} else
 		start_blk = group_blk;
 
+	if (flexbg_size) {
+		int prev_block = 0;
+		if (group && fs->group_desc[group-1].bg_block_bitmap)
+			prev_block = fs->group_desc[group-1].bg_block_bitmap;
+		start_blk = flexbg_offset(fs, group, prev_block, bmap,
+						 0, rem_grps);
+		last_blk = ext2fs_group_last_block(fs, last_grp);
+	}
+
 	if (!fs->group_desc[group].bg_block_bitmap) {
 		retval = ext2fs_get_free_blocks(fs, start_blk, last_blk,
 						1, bmap, &new_blk);
@@ -66,6 +137,22 @@ errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 			return retval;
 		ext2fs_mark_block_bitmap(bmap, new_blk);
 		fs->group_desc[group].bg_block_bitmap = new_blk;
+		if (flexbg_size) {
+			dgrp_t gr = ext2fs_group_of_blk(fs, new_blk);
+			fs->group_desc[gr].bg_free_blocks_count--;
+			fs->super->s_free_blocks_count--;
+			fs->group_desc[gr].bg_flags &= ~EXT2_BG_BLOCK_UNINIT;
+			ext2fs_group_desc_csum_set(fs, gr);
+		}
+	}
+
+	if (flexbg_size) {
+		int prev_block = 0;
+		if (group && fs->group_desc[group-1].bg_inode_bitmap)
+			prev_block = fs->group_desc[group-1].bg_inode_bitmap;
+		start_blk = flexbg_offset(fs, group, prev_block, bmap,
+						 flexbg_size, rem_grps);
+		last_blk = ext2fs_group_last_block(fs, last_grp);
 	}
 
 	if (!fs->group_desc[group].bg_inode_bitmap) {
@@ -78,11 +165,29 @@ errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 			return retval;
 		ext2fs_mark_block_bitmap(bmap, new_blk);
 		fs->group_desc[group].bg_inode_bitmap = new_blk;
+		if (flexbg_size) {
+			dgrp_t gr = ext2fs_group_of_blk(fs, new_blk);
+			fs->group_desc[gr].bg_free_blocks_count--;
+			fs->super->s_free_blocks_count--;
+			fs->group_desc[gr].bg_flags &= ~EXT2_BG_BLOCK_UNINIT;
+			ext2fs_group_desc_csum_set(fs, gr);
+		}
 	}
 
 	/*
 	 * Allocate the inode table
 	 */
+	if (flexbg_size) {
+		int prev_block = 0;
+		if (group && fs->group_desc[group-1].bg_inode_table)
+			prev_block = fs->group_desc[group-1].bg_inode_table;
+		group_blk = flexbg_offset(fs, group, prev_block, bmap,
+						 flexbg_size * 2,
+						 fs->inode_blocks_per_group *
+						 rem_grps);
+		last_blk = ext2fs_group_last_block(fs, last_grp);
+	}
+
 	if (!fs->group_desc[group].bg_inode_table) {
 		retval = ext2fs_get_free_blocks(fs, group_blk, last_blk,
 						fs->inode_blocks_per_group,
@@ -91,12 +196,19 @@ errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 			return retval;
 		for (j=0, blk = new_blk;
 		     j < fs->inode_blocks_per_group;
-		     j++, blk++)
+		     j++, blk++) {
 			ext2fs_mark_block_bitmap(bmap, blk);
+			if (flexbg_size) {
+				dgrp_t gr = ext2fs_group_of_blk(fs, blk);
+				fs->group_desc[gr].bg_free_blocks_count--;
+				fs->super->s_free_blocks_count--;
+				fs->group_desc[gr].bg_flags &= ~EXT2_BG_BLOCK_UNINIT;
+				ext2fs_group_desc_csum_set(fs, gr);
+			}
+		}
 		fs->group_desc[group].bg_inode_table = new_blk;
 	}
 	ext2fs_group_desc_csum_set(fs, group);
-
 	return 0;
 }
 
diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
index 09e1008..396dd59 100644
--- a/lib/ext2fs/initialize.c
+++ b/lib/ext2fs/initialize.c
@@ -159,6 +159,7 @@ errcode_t ext2fs_initialize(const char *name, int flags,
 	set_field(s_first_meta_bg, 0);
 	set_field(s_raid_stride, 0);		/* default stride size: 0 */
 	set_field(s_raid_stripe_width, 0);	/* default stripe width: 0 */
+	set_field(s_log_groups_per_flex, 0);
 	set_field(s_flags, 0);
 	if (super->s_feature_incompat & ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {
 		retval = EXT2_ET_UNSUPP_FEATURE;
@@ -374,6 +375,10 @@ ipg_retry:
 	 * Note that although the block bitmap, inode bitmap, and
 	 * inode table have not been allocated (and in fact won't be
 	 * by this routine), they are accounted for nevertheless.
+	 *
+	 * If FLEX_BG meta-data grouping is used, only account for the
+	 * superblock and group descriptors (the inode tables and
+	 * bitmaps will be accounted for when allocated).
 	 */
 	super->s_free_blocks_count = 0;
 	csum_flag = EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
@@ -390,6 +395,8 @@ ipg_retry:
 			fs->group_desc[i].bg_flags |= EXT2_BG_INODE_UNINIT;
 		}
 		numblocks = ext2fs_reserve_super_and_bgd(fs, i, fs->block_map);
+		if (fs->super->s_log_groups_per_flex)
+			numblocks += 2 + fs->inode_blocks_per_group;
 
 		super->s_free_blocks_count += numblocks;
 		fs->group_desc[i].bg_free_blocks_count = numblocks;
diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index 1e9a203..aa068b3 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -26,6 +26,10 @@ mke2fs \- create an ext2/ext3 filesystem
 .I blocks-per-group
 ]
 [
+.B \-G
+.I number-of-groups
+]
+[
 .B \-i
 .I bytes-per-inode
 ]
@@ -245,6 +249,13 @@ option rather than manipulating the number of blocks per group.)
 This option is generally used by developers who
 are developing test cases.  
 .TP
+.BI \-G " number-of-groups"
+Specify the number of block goups that will be packed together to
+create one large virtual block group on an ext4 filesystem.  This
+improves meta-data locality and performance on meta-data heavy
+workloads.  The number of goups must be a power of 2 and may only be
+specified if the flex_bg filesystem feature is enabled.
+.TP
 .BI \-i " bytes-per-inode"
 Specify the bytes/inode ratio. 
 .B mke2fs
@@ -445,6 +456,11 @@ Use hashed b-trees to speed up lookups in large directories.
 .B filetype
 Store file type information in directory entries.
 .TP
+.B flex_bg
+Allow bitmaps and inode tables for a block group to be placed anywhere
+on the storage media (use with -G option to group meta-data in order
+to create a large virtual block group).
+.TP
 .B has_journal
 Create an ext3 journal (as if using the
 .B \-j
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 61f45aa..e37e510 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -98,8 +98,9 @@ static void usage(void)
 	fprintf(stderr, _("Usage: %s [-c|-l filename] [-b block-size] "
 	"[-f fragment-size]\n\t[-i bytes-per-inode] [-I inode-size] "
 	"[-J journal-options]\n"
-	"\t[-N number-of-inodes] [-m reserved-blocks-percentage] "
-	"[-o creator-os]\n\t[-g blocks-per-group] [-L volume-label] "
+	"\t[-G meta group size] [-N number-of-inodes]\n"
+	"\t[-m reserved-blocks-percentage] [-o creator-os]\n"
+	"\t[-g blocks-per-group] [-L volume-label] "
 	"[-M last-mounted-directory]\n\t[-O feature[,...]] "
 	"[-r fs-revision] [-E extended-option[,...]]\n"
 	"\t[-T fs-type] [-jnqvFSV] device [blocks-count]\n"),
@@ -1096,6 +1097,7 @@ static void PRS(int argc, char *argv[])
 	int		blocksize = 0;
 	int		inode_ratio = 0;
 	int		inode_size = 0;
+	unsigned long	flex_bg_size = 0;
 	double		reserved_ratio = 5.0;
 	int		sector_size = 0;
 	int		show_version_only = 0;
@@ -1180,7 +1182,7 @@ static void PRS(int argc, char *argv[])
 	}
 
 	while ((c = getopt (argc, argv,
-		    "b:cf:g:i:jl:m:no:qr:s:t:vE:FI:J:L:M:N:O:R:ST:V")) != EOF) {
+		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:L:M:N:O:R:ST:V")) != EOF) {
 		switch (c) {
 		case 'b':
 			blocksize = strtol(optarg, &tmp, 0);
@@ -1230,6 +1232,20 @@ static void PRS(int argc, char *argv[])
 				exit(1);
 			}
 			break;
+		case 'G':
+			flex_bg_size = strtoul(optarg, &tmp, 0);
+			if (*tmp) {
+				com_err(program_name, 0,
+					_("Illegal number for flex_bg size"));
+				exit(1);
+			}
+			if (flex_bg_size < 2 ||
+			    (flex_bg_size & (flex_bg_size-1)) != 0) {
+				com_err(program_name, 0,
+					_("flex_bg size must be a power of 2"));
+				exit(1);
+			}
+			break;
 		case 'i':
 			inode_ratio = strtoul(optarg, &tmp, 0);
 			if (inode_ratio < EXT2_MIN_BLOCK_SIZE ||
@@ -1638,6 +1654,19 @@ static void PRS(int argc, char *argv[])
 
 	if (inode_size == 0)
 		inode_size = get_int_from_profile(fs_types, "inode_size", 0);
+	if (!flex_bg_size && (fs_param.s_feature_incompat &
+			      EXT4_FEATURE_INCOMPAT_FLEX_BG))
+		get_int_from_profile(fs_types, "flex_bg_size", 8);
+	if (flex_bg_size) {
+		if (!(fs_param.s_feature_incompat &
+		      EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
+			com_err(program_name, 0,
+				_("Flex_bg feature not enabled, so "
+				  "flex_bg size may not be specified"));
+			exit(1);
+		}
+		fs_param.s_log_groups_per_flex = int_log2(flex_bg_size);
+	}
 
 	if (inode_size && fs_param.s_rev_level >= EXT2_DYNAMIC_REV) {
 		if (inode_size < EXT2_GOOD_OLD_INODE_SIZE ||
diff --git a/misc/mke2fs.conf.5.in b/misc/mke2fs.conf.5.in
index 6734bf3..5dd92d8 100644
--- a/misc/mke2fs.conf.5.in
+++ b/misc/mke2fs.conf.5.in
@@ -301,6 +301,13 @@ specify one on the command line.
 .I inode_size
 This relation specifies the default inode size if the user does not
 specify one on the command line.
+.TP
+.I flex_bg_size
+This relation specifies the number of block goups that will be packed
+together to create one large virtual block group on an ext4 filesystem.
+This improves meta-data locality and performance on meta-data heavy
+workloads.  The number of goups must be a power of 2 and may only be
+specified if the flex_bg filesystem feature is enabled.
 .SH FILES
 .TP
 .I /etc/mke2fs.conf
-- 
1.5.4.1.144.gdfee-dirty

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