diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 53c72ad..a5ba039 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -88,6 +88,7 @@
 		 ext4_group_t block_group, struct ext4_group_desc *gdp)
 {
 	int bit, bit_max;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	unsigned free_blocks, group_blocks;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
@@ -123,7 +124,7 @@
 		bit_max += ext4_bg_num_gdb(sb, block_group);
 	}
 
-	if (block_group == sbi->s_groups_count - 1) {
+	if (block_group == ngroups - 1) {
 		/*
 		 * Even though mke2fs always initialize first and last group
 		 * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
@@ -131,7 +132,7 @@
 		 */
 		group_blocks = ext4_blocks_count(sbi->s_es) -
 			le32_to_cpu(sbi->s_es->s_first_data_block) -
-			(EXT4_BLOCKS_PER_GROUP(sb) * (sbi->s_groups_count - 1));
+			(EXT4_BLOCKS_PER_GROUP(sb) * (ngroups - 1));
 	} else {
 		group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
 	}
@@ -205,18 +206,18 @@
 {
 	unsigned int group_desc;
 	unsigned int offset;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	struct ext4_group_desc *desc;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
-	if (block_group >= sbi->s_groups_count) {
+	if (block_group >= ngroups) {
 		ext4_error(sb, "ext4_get_group_desc",
 			   "block_group >= groups_count - "
 			   "block_group = %u, groups_count = %u",
-			   block_group, sbi->s_groups_count);
+			   block_group, ngroups);
 
 		return NULL;
 	}
-	smp_rmb();
 
 	group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 	offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
@@ -665,7 +666,7 @@
 	ext4_fsblk_t desc_count;
 	struct ext4_group_desc *gdp;
 	ext4_group_t i;
-	ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 #ifdef EXT4FS_DEBUG
 	struct ext4_super_block *es;
 	ext4_fsblk_t bitmap_count;
@@ -677,7 +678,6 @@
 	bitmap_count = 0;
 	gdp = NULL;
 
-	smp_rmb();
 	for (i = 0; i < ngroups; i++) {
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
@@ -700,7 +700,6 @@
 	return bitmap_count;
 #else
 	desc_count = 0;
-	smp_rmb();
 	for (i = 0; i < ngroups; i++) {
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index d0f15ef..02ec44b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1228,6 +1228,18 @@
 	 return grp_info[indexv][indexh];
 }
 
+/*
+ * Reading s_groups_count requires using smp_rmb() afterwards.  See
+ * the locking protocol documented in the comments of ext4_group_add()
+ * in resize.c
+ */
+static inline ext4_group_t ext4_get_groups_count(struct super_block *sb)
+{
+	ext4_group_t	ngroups = EXT4_SB(sb)->s_groups_count;
+
+	smp_rmb();
+	return ngroups;
+}
 
 static inline ext4_group_t ext4_flex_group(struct ext4_sb_info *sbi,
 					     ext4_group_t block_group)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index f18e0a0..55ba419 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -316,7 +316,7 @@
 static int find_group_dir(struct super_block *sb, struct inode *parent,
 				ext4_group_t *best_group)
 {
-	ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	unsigned int freei, avefreei;
 	struct ext4_group_desc *desc, *best_desc = NULL;
 	ext4_group_t group;
@@ -353,7 +353,7 @@
 	struct flex_groups *flex_group = sbi->s_flex_groups;
 	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
 	ext4_group_t parent_fbg_group = ext4_flex_group(sbi, parent_group);
-	ext4_group_t ngroups = sbi->s_groups_count;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	int flex_size = ext4_flex_bg_size(sbi);
 	ext4_group_t best_flex = parent_fbg_group;
 	int blocks_per_flex = sbi->s_blocks_per_group * flex_size;
@@ -362,7 +362,7 @@
 	ext4_group_t n_fbg_groups;
 	ext4_group_t i;
 
-	n_fbg_groups = (sbi->s_groups_count + flex_size - 1) >>
+	n_fbg_groups = (ngroups + flex_size - 1) >>
 		sbi->s_log_groups_per_flex;
 
 find_close_to_parent:
@@ -478,20 +478,21 @@
 {
 	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	ext4_group_t ngroups = sbi->s_groups_count;
+	ext4_group_t real_ngroups = ext4_get_groups_count(sb);
 	int inodes_per_group = EXT4_INODES_PER_GROUP(sb);
 	unsigned int freei, avefreei;
 	ext4_fsblk_t freeb, avefreeb;
 	unsigned int ndirs;
 	int max_dirs, min_inodes;
 	ext4_grpblk_t min_blocks;
-	ext4_group_t i, grp, g;
+	ext4_group_t i, grp, g, ngroups;
 	struct ext4_group_desc *desc;
 	struct orlov_stats stats;
 	int flex_size = ext4_flex_bg_size(sbi);
 
+	ngroups = real_ngroups;
 	if (flex_size > 1) {
-		ngroups = (ngroups + flex_size - 1) >>
+		ngroups = (real_ngroups + flex_size - 1) >>
 			sbi->s_log_groups_per_flex;
 		parent_group >>= sbi->s_log_groups_per_flex;
 	}
@@ -543,7 +544,7 @@
 		 */
 		grp *= flex_size;
 		for (i = 0; i < flex_size; i++) {
-			if (grp+i >= sbi->s_groups_count)
+			if (grp+i >= real_ngroups)
 				break;
 			desc = ext4_get_group_desc(sb, grp+i, NULL);
 			if (desc && ext4_free_inodes_count(sb, desc)) {
@@ -583,7 +584,7 @@
 	}
 
 fallback:
-	ngroups = sbi->s_groups_count;
+	ngroups = real_ngroups;
 	avefreei = freei / ngroups;
 fallback_retry:
 	parent_group = EXT4_I(parent)->i_block_group;
@@ -613,9 +614,8 @@
 			    ext4_group_t *group, int mode)
 {
 	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
-	ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
+	ext4_group_t i, last, ngroups = ext4_get_groups_count(sb);
 	struct ext4_group_desc *desc;
-	ext4_group_t i, last;
 	int flex_size = ext4_flex_bg_size(EXT4_SB(sb));
 
 	/*
@@ -799,11 +799,10 @@
 	struct super_block *sb;
 	struct buffer_head *inode_bitmap_bh = NULL;
 	struct buffer_head *group_desc_bh;
-	ext4_group_t group = 0;
+	ext4_group_t ngroups, group = 0;
 	unsigned long ino = 0;
 	struct inode *inode;
 	struct ext4_group_desc *gdp = NULL;
-	struct ext4_super_block *es;
 	struct ext4_inode_info *ei;
 	struct ext4_sb_info *sbi;
 	int ret2, err = 0;
@@ -818,15 +817,14 @@
 		return ERR_PTR(-EPERM);
 
 	sb = dir->i_sb;
+	ngroups = ext4_get_groups_count(sb);
 	trace_mark(ext4_request_inode, "dev %s dir %lu mode %d", sb->s_id,
 		   dir->i_ino, mode);
 	inode = new_inode(sb);
 	if (!inode)
 		return ERR_PTR(-ENOMEM);
 	ei = EXT4_I(inode);
-
 	sbi = EXT4_SB(sb);
-	es = sbi->s_es;
 
 	if (sbi->s_log_groups_per_flex && test_opt(sb, OLDALLOC)) {
 		ret2 = find_group_flex(sb, dir, &group);
@@ -856,7 +854,7 @@
 	if (ret2 == -1)
 		goto out;
 
-	for (i = 0; i < sbi->s_groups_count; i++) {
+	for (i = 0; i < ngroups; i++) {
 		err = -EIO;
 
 		gdp = ext4_get_group_desc(sb, group, &group_desc_bh);
@@ -917,7 +915,7 @@
 		 * group descriptor metadata has not yet been updated.
 		 * So we just go onto the next blockgroup.
 		 */
-		if (++group == sbi->s_groups_count)
+		if (++group == ngroups)
 			group = 0;
 	}
 	err = -ENOSPC;
@@ -1158,7 +1156,7 @@
 {
 	unsigned long desc_count;
 	struct ext4_group_desc *gdp;
-	ext4_group_t i;
+	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 #ifdef EXT4FS_DEBUG
 	struct ext4_super_block *es;
 	unsigned long bitmap_count, x;
@@ -1168,7 +1166,7 @@
 	desc_count = 0;
 	bitmap_count = 0;
 	gdp = NULL;
-	for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
+	for (i = 0; i < ngroups; i++) {
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
 			continue;
@@ -1190,7 +1188,7 @@
 	return desc_count;
 #else
 	desc_count = 0;
-	for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
+	for (i = 0; i < ngroups; i++) {
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
 			continue;
@@ -1205,9 +1203,9 @@
 unsigned long ext4_count_dirs(struct super_block * sb)
 {
 	unsigned long count = 0;
-	ext4_group_t i;
+	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 
-	for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
+	for (i = 0; i < ngroups; i++) {
 		struct ext4_group_desc *gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
 			continue;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 96f3366..4e7f363 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4965,7 +4965,8 @@
  */
 int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk)
 {
-	int groups, gdpblocks;
+	ext4_group_t groups, ngroups = ext4_get_groups_count(inode->i_sb);
+	int gdpblocks;
 	int idxblocks;
 	int ret = 0;
 
@@ -4992,8 +4993,8 @@
 		groups += nrblocks;
 
 	gdpblocks = groups;
-	if (groups > EXT4_SB(inode->i_sb)->s_groups_count)
-		groups = EXT4_SB(inode->i_sb)->s_groups_count;
+	if (groups > ngroups)
+		groups = ngroups;
 	if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
 		gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;
 
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f871677..c3af9e6 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -739,6 +739,7 @@
 
 static int ext4_mb_init_cache(struct page *page, char *incore)
 {
+	ext4_group_t ngroups;
 	int blocksize;
 	int blocks_per_page;
 	int groups_per_page;
@@ -757,6 +758,7 @@
 
 	inode = page->mapping->host;
 	sb = inode->i_sb;
+	ngroups = ext4_get_groups_count(sb);
 	blocksize = 1 << inode->i_blkbits;
 	blocks_per_page = PAGE_CACHE_SIZE / blocksize;
 
@@ -780,7 +782,7 @@
 	for (i = 0; i < groups_per_page; i++) {
 		struct ext4_group_desc *desc;
 
-		if (first_group + i >= EXT4_SB(sb)->s_groups_count)
+		if (first_group + i >= ngroups)
 			break;
 
 		err = -EIO;
@@ -852,7 +854,7 @@
 		struct ext4_group_info *grinfo;
 
 		group = (first_block + i) >> 1;
-		if (group >= EXT4_SB(sb)->s_groups_count)
+		if (group >= ngroups)
 			break;
 
 		/*
@@ -1788,6 +1790,7 @@
 	int block, pnum;
 	int blocks_per_page;
 	int groups_per_page;
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	ext4_group_t first_group;
 	struct ext4_group_info *grp;
 
@@ -1807,7 +1810,7 @@
 	/* read all groups the page covers into the cache */
 	for (i = 0; i < groups_per_page; i++) {
 
-		if ((first_group + i) >= EXT4_SB(sb)->s_groups_count)
+		if ((first_group + i) >= ngroups)
 			break;
 		grp = ext4_get_group_info(sb, first_group + i);
 		/* take all groups write allocation
@@ -1945,8 +1948,7 @@
 static noinline_for_stack int
 ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 {
-	ext4_group_t group;
-	ext4_group_t i;
+	ext4_group_t ngroups, group, i;
 	int cr;
 	int err = 0;
 	int bsbits;
@@ -1957,6 +1959,7 @@
 
 	sb = ac->ac_sb;
 	sbi = EXT4_SB(sb);
+	ngroups = ext4_get_groups_count(sb);
 	BUG_ON(ac->ac_status == AC_STATUS_FOUND);
 
 	/* first, try the goal */
@@ -2017,11 +2020,11 @@
 		 */
 		group = ac->ac_g_ex.fe_group;
 
-		for (i = 0; i < EXT4_SB(sb)->s_groups_count; group++, i++) {
+		for (i = 0; i < ngroups; group++, i++) {
 			struct ext4_group_info *grp;
 			struct ext4_group_desc *desc;
 
-			if (group == EXT4_SB(sb)->s_groups_count)
+			if (group == ngroups)
 				group = 0;
 
 			/* quick check to skip empty groups */
@@ -2315,12 +2318,10 @@
 static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
 {
 	struct super_block *sb = seq->private;
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	ext4_group_t group;
 
-	if (*pos < 0 || *pos >= sbi->s_groups_count)
+	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
 		return NULL;
-
 	group = *pos + 1;
 	return (void *) ((unsigned long) group);
 }
@@ -2328,11 +2329,10 @@
 static void *ext4_mb_seq_groups_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	struct super_block *sb = seq->private;
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	ext4_group_t group;
 
 	++*pos;
-	if (*pos < 0 || *pos >= sbi->s_groups_count)
+	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
 		return NULL;
 	group = *pos + 1;
 	return (void *) ((unsigned long) group);
@@ -2587,6 +2587,7 @@
 
 static int ext4_mb_init_backend(struct super_block *sb)
 {
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	ext4_group_t i;
 	int metalen;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
@@ -2598,7 +2599,7 @@
 	struct ext4_group_desc *desc;
 
 	/* This is the number of blocks used by GDT */
-	num_meta_group_infos = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) -
+	num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -
 				1) >> EXT4_DESC_PER_BLOCK_BITS(sb);
 
 	/*
@@ -2644,7 +2645,7 @@
 	for (i = 0; i < num_meta_group_infos; i++) {
 		if ((i + 1) == num_meta_group_infos)
 			metalen = sizeof(*meta_group_info) *
-				(sbi->s_groups_count -
+				(ngroups -
 					(i << EXT4_DESC_PER_BLOCK_BITS(sb)));
 		meta_group_info = kmalloc(metalen, GFP_KERNEL);
 		if (meta_group_info == NULL) {
@@ -2655,7 +2656,7 @@
 		sbi->s_group_info[i] = meta_group_info;
 	}
 
-	for (i = 0; i < sbi->s_groups_count; i++) {
+	for (i = 0; i < ngroups; i++) {
 		desc = ext4_get_group_desc(sb, i, NULL);
 		if (desc == NULL) {
 			printk(KERN_ERR
@@ -2781,13 +2782,14 @@
 
 int ext4_mb_release(struct super_block *sb)
 {
+	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	ext4_group_t i;
 	int num_meta_group_infos;
 	struct ext4_group_info *grinfo;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
 	if (sbi->s_group_info) {
-		for (i = 0; i < sbi->s_groups_count; i++) {
+		for (i = 0; i < ngroups; i++) {
 			grinfo = ext4_get_group_info(sb, i);
 #ifdef DOUBLE_CHECK
 			kfree(grinfo->bb_bitmap);
@@ -2797,7 +2799,7 @@
 			ext4_unlock_group(sb, i);
 			kfree(grinfo);
 		}
-		num_meta_group_infos = (sbi->s_groups_count +
+		num_meta_group_infos = (ngroups +
 				EXT4_DESC_PER_BLOCK(sb) - 1) >>
 			EXT4_DESC_PER_BLOCK_BITS(sb);
 		for (i = 0; i < num_meta_group_infos; i++)
@@ -4121,7 +4123,7 @@
 static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
 {
 	struct super_block *sb = ac->ac_sb;
-	ext4_group_t i;
+	ext4_group_t ngroups, i;
 
 	printk(KERN_ERR "EXT4-fs: Can't allocate:"
 			" Allocation context details:\n");
@@ -4145,7 +4147,8 @@
 	printk(KERN_ERR "EXT4-fs: %lu scanned, %d found\n", ac->ac_ex_scanned,
 		ac->ac_found);
 	printk(KERN_ERR "EXT4-fs: groups: \n");
-	for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
+	ngroups = ext4_get_groups_count(sb);
+	for (i = 0; i < ngroups; i++) {
 		struct ext4_group_info *grp = ext4_get_group_info(sb, i);
 		struct ext4_prealloc_space *pa;
 		ext4_grpblk_t start;
@@ -4469,13 +4472,13 @@
 
 static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
 {
-	ext4_group_t i;
+	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 	int ret;
 	int freed = 0;
 
 	trace_mark(ext4_mb_discard_preallocations, "dev %s needed %d",
 		   sb->s_id, needed);
-	for (i = 0; i < EXT4_SB(sb)->s_groups_count && needed > 0; i++) {
+	for (i = 0; i < ngroups && needed > 0; i++) {
 		ret = ext4_mb_discard_group_preallocations(sb, i, needed);
 		freed += ret;
 		needed -= ret;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 68c3a44..fcd7b24 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3557,9 +3557,8 @@
 	if (test_opt(sb, MINIX_DF)) {
 		sbi->s_overhead_last = 0;
 	} else if (sbi->s_blocks_last != ext4_blocks_count(es)) {
-		ext4_group_t ngroups = sbi->s_groups_count, i;
+		ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 		ext4_fsblk_t overhead = 0;
-		smp_rmb();
 
 		/*
 		 * Compute the overhead (FS structures).  This is constant