[PATCH 0/9 v3] meta_bg online resize patches

[PATCH 0/9 v3] meta_bg online resize patches

[Theodore Ts'o]

Here is an updated meta_bg online resize patches.  This set of patches
needs to be paired with a set of e2fsprogs patches to enable online
resize.  With this set of patches, we can start with a file system which
uses the resize_inode scheme of reserved gdt blocks, but after we have
consumed all of the reserved gdt blocks, the kernel will switch over to
using the meta_bg scheme of online growth.

This works both with traditional 32-bit filesystems as well newer 64-bit
file systems.  As an example of the sort of on-line resizes that will
work, my testing included:

*  mke2fs -t ext4 /dev/vdc 2M ; mount /dev/vdc; resize2fs /dev/vdc 8G
*  mke2fs -t ext2 /dev/vdc 2M ; mount /dev/vdc; resize2fs /dev/vdc 8G
*  mke2fs -t ext4 -O 64bit /dev/vdc 12T ; mount /dev/vdc; resize2fs /dev/vdc 18T

Theodore Ts'o (6):
  ext4: grow the s_flex_groups array as needed when resizing
  ext4: grow the s_group_info array as needed
  ext4: set bg_itable_unused when resizing
  ext4: convert file system to meta_bg if needed during resizing
  ext4: log a resize update to the console every 10 seconds
  ext4: advertise the fact that the kernel supports meta_bg resizing

Yongqiang Yang (3):
  ext4: don't copy non-existent gdt blocks when resizing
  ext4: avoid duplicate writes of the backup bg descriptor blocks
  ext4: add online resizing support for meta_bg and 64-bit file systems

 fs/ext4/ext4.h    |   6 +
 fs/ext4/ioctl.c   |  15 ---
 fs/ext4/mballoc.c |  79 ++++++-----
 fs/ext4/resize.c  | 386 +++++++++++++++++++++++++++++++++++++++++++++---------
 fs/ext4/super.c   |  50 +++++--
 5 files changed, 405 insertions(+), 131 deletions(-)

-- 
1.7.12.rc0.22.gcdd159b

[PATCH 1/9] ext4: don't copy non-existent gdt blocks when resizing

[Theodore Ts'o]

From: Yongqiang Yang <xiaoqiangnk@gmail.com>

The resize code was copying blocks at the beginning of each block
group in order to copy the superblock and block group descriptor table
(gdt) blocks.  This was, unfortunately, being done even for block
groups that did not have super blocks or gdt blocks.  This is a
complete waste of perfectly good I/O bandwidth, to skip writing those
blocks for sparse bg's.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
---
 fs/ext4/resize.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 591f4bd..a0ee26c 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -456,6 +456,9 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
 		gdblocks = ext4_bg_num_gdb(sb, group);
 		start = ext4_group_first_block_no(sb, group);
 
+		if (!ext4_bg_has_super(sb, group))
+			goto handle_itb;
+
 		/* Copy all of the GDT blocks into the backup in this group */
 		for (j = 0, block = start + 1; j < gdblocks; j++, block++) {
 			struct buffer_head *gdb;
@@ -498,6 +501,7 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
 				goto out;
 		}
 
+handle_itb:
 		/* Initialize group tables of the grop @group */
 		if (!(bg_flags[i] & EXT4_BG_INODE_ZEROED))
 			goto handle_bb;
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 2/9] ext4: avoid duplicate writes of the backup bg descriptor blocks

[Theodore Ts'o]

From: Yongqiang Yang <xiaoqiangnk@gmail.com>

The resize code was needlessly writing the backup block group
descriptor blocks multiple times (once per block group) during an
online resize.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
---
 fs/ext4/resize.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a0ee26c..365d800 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1358,13 +1358,15 @@ exit_journal:
 		err = err2;
 
 	if (!err) {
-		int i;
+		int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
+		int gdb_num_end = ((group + flex_gd->count - 1) /
+				   EXT4_DESC_PER_BLOCK(sb));
+
 		update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
 			       sizeof(struct ext4_super_block));
-		for (i = 0; i < flex_gd->count; i++, group++) {
+		for (; gdb_num <= gdb_num_end; gdb_num++) {
 			struct buffer_head *gdb_bh;
-			int gdb_num;
-			gdb_num = group / EXT4_BLOCKS_PER_GROUP(sb);
+
 			gdb_bh = sbi->s_group_desc[gdb_num];
 			update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
 				       gdb_bh->b_size);
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 3/9] ext4: grow the s_flex_groups array as needed when resizing

[Theodore Ts'o]

Previously, we allocated the s_flex_groups array to the maximum size
that the file system could be resized.  There was two problems with
this approach.  First, it wasted memory in the common case where the
file system was not resized.  Secondly, once we start allowing online
resizing using the meta_bg scheme, there is no maximum size that the
file system can be resized.  So instead, we need to grow the
s_flex_groups at inline resize time.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/ext4.h   |  3 +++
 fs/ext4/resize.c | 14 +++++++++-----
 fs/ext4/super.c  | 48 +++++++++++++++++++++++++++++++++++-------------
 3 files changed, 47 insertions(+), 18 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0df5ee1..464cff7 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1276,6 +1276,7 @@ struct ext4_sb_info {
 
 	unsigned int s_log_groups_per_flex;
 	struct flex_groups *s_flex_groups;
+	ext4_group_t s_flex_groups_allocated;
 
 	/* workqueue for dio unwritten */
 	struct workqueue_struct *dio_unwritten_wq;
@@ -2055,6 +2056,8 @@ extern void ext4_superblock_csum_set(struct super_block *sb,
 extern void *ext4_kvmalloc(size_t size, gfp_t flags);
 extern void *ext4_kvzalloc(size_t size, gfp_t flags);
 extern void ext4_kvfree(void *ptr);
+extern int ext4_alloc_flex_bg_array(struct super_block *sb,
+				    ext4_group_t ngroup);
 extern __printf(4, 5)
 void __ext4_error(struct super_block *, const char *, unsigned int,
 		  const char *, ...);
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 365d800..3f5c67b 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1503,6 +1503,10 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
 	if (err)
 		goto out;
 
+	err = ext4_alloc_flex_bg_array(sb, input->group + 1);
+	if (err)
+		return err;
+
 	flex_gd.count = 1;
 	flex_gd.groups = input;
 	flex_gd.bg_flags = &bg_flags;
@@ -1662,7 +1666,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	unsigned long n_desc_blocks;
 	unsigned long o_desc_blocks;
 	unsigned long desc_blocks;
-	int err = 0, flexbg_size = 1;
+	int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
 
 	o_blocks_count = ext4_blocks_count(es);
 
@@ -1721,13 +1725,13 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 			goto out;
 	}
 
-	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
-	    es->s_log_groups_per_flex)
-		flexbg_size = 1 << es->s_log_groups_per_flex;
-
 	if (ext4_blocks_count(es) == n_blocks_count)
 		goto out;
 
+	err = ext4_alloc_flex_bg_array(sb, n_group + 1);
+	if (err)
+		return err;
+
 	flex_gd = alloc_flex_gd(flexbg_size);
 	if (flex_gd == NULL) {
 		err = -ENOMEM;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b875ff5..b8de488 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1925,15 +1925,45 @@ done:
 	return res;
 }
 
+int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct flex_groups *new_groups;
+	int size;
+
+	if (!sbi->s_log_groups_per_flex)
+		return 0;
+
+	size = ext4_flex_group(sbi, ngroup - 1) + 1;
+	if (size <= sbi->s_flex_groups_allocated)
+		return 0;
+
+	size = roundup_pow_of_two(size * sizeof(struct flex_groups));
+	new_groups = ext4_kvzalloc(size, GFP_KERNEL);
+	if (!new_groups) {
+		ext4_msg(sb, KERN_ERR, "not enough memory for %d flex groups",
+			 size / (int) sizeof(struct flex_groups));
+		return -ENOMEM;
+	}
+
+	if (sbi->s_flex_groups) {
+		memcpy(new_groups, sbi->s_flex_groups,
+		       (sbi->s_flex_groups_allocated *
+			sizeof(struct flex_groups)));
+		ext4_kvfree(sbi->s_flex_groups);
+	}
+	sbi->s_flex_groups = new_groups;
+	sbi->s_flex_groups_allocated = size / sizeof(struct flex_groups);
+	return 0;
+}
+
 static int ext4_fill_flex_info(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_group_desc *gdp = NULL;
-	ext4_group_t flex_group_count;
 	ext4_group_t flex_group;
 	unsigned int groups_per_flex = 0;
-	size_t size;
-	int i;
+	int i, err;
 
 	sbi->s_log_groups_per_flex = sbi->s_es->s_log_groups_per_flex;
 	if (sbi->s_log_groups_per_flex < 1 || sbi->s_log_groups_per_flex > 31) {
@@ -1942,17 +1972,9 @@ static int ext4_fill_flex_info(struct super_block *sb)
 	}
 	groups_per_flex = 1 << sbi->s_log_groups_per_flex;
 
-	/* We allocate both existing and potentially added groups */
-	flex_group_count = ((sbi->s_groups_count + groups_per_flex - 1) +
-			((le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) + 1) <<
-			      EXT4_DESC_PER_BLOCK_BITS(sb))) / groups_per_flex;
-	size = flex_group_count * sizeof(struct flex_groups);
-	sbi->s_flex_groups = ext4_kvzalloc(size, GFP_KERNEL);
-	if (sbi->s_flex_groups == NULL) {
-		ext4_msg(sb, KERN_ERR, "not enough memory for %u flex groups",
-			 flex_group_count);
+	err = ext4_alloc_flex_bg_array(sb, sbi->s_groups_count);
+	if (err)
 		goto failed;
-	}
 
 	for (i = 0; i < sbi->s_groups_count; i++) {
 		gdp = ext4_get_group_desc(sb, i, NULL);
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 4/9] ext4: grow the s_group_info array as needed

[Theodore Ts'o]

Previously we allocated the s_group_info array with enough space for
any future possible growth of the file system via online resize.  This
is unfortunate because it wastes memory, and it doesn't work for the
meta_bg scheme, since there is no limit based on the number of
reserved gdt blocks.  So add the code to grow the s_group_info array
as needed.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/ext4.h    |  3 +++
 fs/ext4/mballoc.c | 79 +++++++++++++++++++++++++++----------------------------
 fs/ext4/resize.c  |  8 ++++++
 3 files changed, 50 insertions(+), 40 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 464cff7..8b6902c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1233,6 +1233,7 @@ struct ext4_sb_info {
 	spinlock_t s_md_lock;
 	unsigned short *s_mb_offsets;
 	unsigned int *s_mb_maxs;
+	unsigned int s_group_info_size;
 
 	/* tunables */
 	unsigned long s_stripe;
@@ -1971,6 +1972,8 @@ extern void ext4_exit_mballoc(void);
 extern void ext4_free_blocks(handle_t *handle, struct inode *inode,
 			     struct buffer_head *bh, ext4_fsblk_t block,
 			     unsigned long count, int flags);
+extern int ext4_mb_alloc_groupinfo(struct super_block *sb,
+				   ext4_group_t ngroups);
 extern int ext4_mb_add_groupinfo(struct super_block *sb,
 		ext4_group_t i, struct ext4_group_desc *desc);
 extern int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 6873571..2102c20 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -24,6 +24,7 @@
 #include "ext4_jbd2.h"
 #include "mballoc.h"
 #include <linux/debugfs.h>
+#include <linux/log2.h>
 #include <linux/slab.h>
 #include <trace/events/ext4.h>
 
@@ -2163,6 +2164,39 @@ static struct kmem_cache *get_groupinfo_cache(int blocksize_bits)
 	return cachep;
 }
 
+/*
+ * Allocate the top-level s_group_info array for the specified number
+ * of groups
+ */
+int ext4_mb_alloc_groupinfo(struct super_block *sb, ext4_group_t ngroups)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	unsigned size;
+	struct ext4_group_info ***new_groupinfo;
+
+	size = (ngroups + EXT4_DESC_PER_BLOCK(sb) - 1) >>
+		EXT4_DESC_PER_BLOCK_BITS(sb);
+	if (size <= sbi->s_group_info_size)
+		return 0;
+
+	size = roundup_pow_of_two(sizeof(*sbi->s_group_info) * size);
+	new_groupinfo = ext4_kvzalloc(size, GFP_KERNEL);
+	if (!new_groupinfo) {
+		ext4_msg(sb, KERN_ERR, "can't allocate buddy meta group");
+		return -ENOMEM;
+	}
+	if (sbi->s_group_info) {
+		memcpy(new_groupinfo, sbi->s_group_info,
+		       sbi->s_group_info_size * sizeof(*sbi->s_group_info));
+		ext4_kvfree(sbi->s_group_info);
+	}
+	sbi->s_group_info = new_groupinfo;
+	sbi->s_group_info_size = size / sizeof(*sbi->s_group_info);
+	ext4_debug("allocated s_groupinfo array for %d meta_bg's\n", 
+		   sbi->s_group_info_size);
+	return 0;
+}
+
 /* Create and initialize ext4_group_info data for the given group. */
 int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 			  struct ext4_group_desc *desc)
@@ -2252,49 +2286,14 @@ static int ext4_mb_init_backend(struct super_block *sb)
 	ext4_group_t ngroups = ext4_get_groups_count(sb);
 	ext4_group_t i;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	struct ext4_super_block *es = sbi->s_es;
-	int num_meta_group_infos;
-	int num_meta_group_infos_max;
-	int array_size;
+	int err;
 	struct ext4_group_desc *desc;
 	struct kmem_cache *cachep;
 
-	/* This is the number of blocks used by GDT */
-	num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -
-				1) >> EXT4_DESC_PER_BLOCK_BITS(sb);
-
-	/*
-	 * This is the total number of blocks used by GDT including
-	 * the number of reserved blocks for GDT.
-	 * The s_group_info array is allocated with this value
-	 * to allow a clean online resize without a complex
-	 * manipulation of pointer.
-	 * The drawback is the unused memory when no resize
-	 * occurs but it's very low in terms of pages
-	 * (see comments below)
-	 * Need to handle this properly when META_BG resizing is allowed
-	 */
-	num_meta_group_infos_max = num_meta_group_infos +
-				le16_to_cpu(es->s_reserved_gdt_blocks);
+	err = ext4_mb_alloc_groupinfo(sb, ngroups);
+	if (err)
+		return err;
 
-	/*
-	 * array_size is the size of s_group_info array. We round it
-	 * to the next power of two because this approximation is done
-	 * internally by kmalloc so we can have some more memory
-	 * for free here (e.g. may be used for META_BG resize).
-	 */
-	array_size = 1;
-	while (array_size < sizeof(*sbi->s_group_info) *
-	       num_meta_group_infos_max)
-		array_size = array_size << 1;
-	/* An 8TB filesystem with 64-bit pointers requires a 4096 byte
-	 * kmalloc. A 128kb malloc should suffice for a 256TB filesystem.
-	 * So a two level scheme suffices for now. */
-	sbi->s_group_info = ext4_kvzalloc(array_size, GFP_KERNEL);
-	if (sbi->s_group_info == NULL) {
-		ext4_msg(sb, KERN_ERR, "can't allocate buddy meta group");
-		return -ENOMEM;
-	}
 	sbi->s_buddy_cache = new_inode(sb);
 	if (sbi->s_buddy_cache == NULL) {
 		ext4_msg(sb, KERN_ERR, "can't get new inode");
@@ -2322,7 +2321,7 @@ err_freebuddy:
 	cachep = get_groupinfo_cache(sb->s_blocksize_bits);
 	while (i-- > 0)
 		kmem_cache_free(cachep, ext4_get_group_info(sb, i));
-	i = num_meta_group_infos;
+	i = sbi->s_group_info_size;
 	while (i-- > 0)
 		kfree(sbi->s_group_info[i]);
 	iput(sbi->s_buddy_cache);
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 3f5c67b..f288933 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1507,6 +1507,10 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
 	if (err)
 		return err;
 
+	err = ext4_mb_alloc_groupinfo(sb, input->group + 1);
+	if (err)
+		goto out;
+
 	flex_gd.count = 1;
 	flex_gd.groups = input;
 	flex_gd.bg_flags = &bg_flags;
@@ -1732,6 +1736,10 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	if (err)
 		return err;
 
+	err = ext4_mb_alloc_groupinfo(sb, n_group + 1);
+	if (err)
+		goto out;
+
 	flex_gd = alloc_flex_gd(flexbg_size);
 	if (flex_gd == NULL) {
 		err = -ENOMEM;
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 5/9] ext4: add online resizing support for meta_bg and 64-bit file systems

[Theodore Ts'o]

From: Yongqiang Yang <xiaoqiangnk@gmail.com>

This patch adds support for resizing file systems with the meta_bg and
64bit features.

[ Added a fix by tytso to fix a divide by zero when resizing a
  filesystem from 14 TB to 18TB.  Also fixed overhead accounting for
  meta_bg file systems.]

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/ioctl.c  |  15 ----
 fs/ext4/resize.c | 215 ++++++++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 165 insertions(+), 65 deletions(-)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 7f7dad7..8b84fe2 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -365,26 +365,11 @@ group_add_out:
 			return -EOPNOTSUPP;
 		}
 
-		if (EXT4_HAS_INCOMPAT_FEATURE(sb,
-			       EXT4_FEATURE_INCOMPAT_META_BG)) {
-			ext4_msg(sb, KERN_ERR,
-				 "Online resizing not (yet) supported with meta_bg");
-			return -EOPNOTSUPP;
-		}
-
 		if (copy_from_user(&n_blocks_count, (__u64 __user *)arg,
 				   sizeof(__u64))) {
 			return -EFAULT;
 		}
 
-		if (n_blocks_count > MAX_32_NUM &&
-		    !EXT4_HAS_INCOMPAT_FEATURE(sb,
-					       EXT4_FEATURE_INCOMPAT_64BIT)) {
-			ext4_msg(sb, KERN_ERR,
-				 "File system only supports 32-bit block numbers");
-			return -EOPNOTSUPP;
-		}
-
 		err = ext4_resize_begin(sb);
 		if (err)
 			return err;
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index f288933..7adc088 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -45,6 +45,28 @@ void ext4_resize_end(struct super_block *sb)
 	smp_mb__after_clear_bit();
 }
 
+static ext4_group_t ext4_meta_bg_first_group(struct super_block *sb,
+					     ext4_group_t group) {
+	return (group >> EXT4_DESC_PER_BLOCK_BITS(sb)) <<
+	       EXT4_DESC_PER_BLOCK_BITS(sb);
+}
+
+static ext4_fsblk_t ext4_meta_bg_first_block_no(struct super_block *sb,
+					     ext4_group_t group) {
+	group = ext4_meta_bg_first_group(sb, group);
+	return ext4_group_first_block_no(sb, group);
+}
+
+static ext4_grpblk_t ext4_group_overhead_blocks(struct super_block *sb,
+						ext4_group_t group) {
+	ext4_grpblk_t overhead;
+	overhead = ext4_bg_num_gdb(sb, group);
+	if (ext4_bg_has_super(sb, group))
+		overhead += 1 +
+			  le16_to_cpu(EXT4_SB(sb)->s_es->s_reserved_gdt_blocks);
+	return overhead;
+}
+
 #define outside(b, first, last)	((b) < (first) || (b) >= (last))
 #define inside(b, first, last)	((b) >= (first) && (b) < (last))
 
@@ -57,9 +79,7 @@ static int verify_group_input(struct super_block *sb,
 	ext4_fsblk_t end = start + input->blocks_count;
 	ext4_group_t group = input->group;
 	ext4_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;
-	unsigned overhead = ext4_bg_has_super(sb, group) ?
-		(1 + ext4_bg_num_gdb(sb, group) +
-		 le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
+	unsigned overhead = ext4_group_overhead_blocks(sb, group);
 	ext4_fsblk_t metaend = start + overhead;
 	struct buffer_head *bh = NULL;
 	ext4_grpblk_t free_blocks_count, offset;
@@ -209,7 +229,6 @@ static int ext4_alloc_group_tables(struct super_block *sb,
 				int flexbg_size)
 {
 	struct ext4_new_group_data *group_data = flex_gd->groups;
-	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 	ext4_fsblk_t start_blk;
 	ext4_fsblk_t last_blk;
 	ext4_group_t src_group;
@@ -234,19 +253,19 @@ next_group:
 	start_blk = ext4_group_first_block_no(sb, src_group);
 	last_blk = start_blk + group_data[src_group - group].blocks_count;
 
-	overhead = ext4_bg_has_super(sb, src_group) ?
-		   (1 + ext4_bg_num_gdb(sb, src_group) +
-		    le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
+	overhead = ext4_group_overhead_blocks(sb, src_group);
 
 	start_blk += overhead;
 
 	/* We collect contiguous blocks as much as possible. */
 	src_group++;
-	for (; src_group <= last_group; src_group++)
-		if (!ext4_bg_has_super(sb, src_group))
+	for (; src_group <= last_group; src_group++) {
+		overhead = ext4_group_overhead_blocks(sb, src_group);
+		if (overhead != 0)
 			last_blk += group_data[src_group - group].blocks_count;
 		else
 			break;
+	}
 
 	/* Allocate block bitmaps */
 	for (; bb_index < flex_gd->count; bb_index++) {
@@ -438,11 +457,13 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
 	ext4_group_t group, count;
 	struct buffer_head *bh = NULL;
 	int reserved_gdb, i, j, err = 0, err2;
+	int meta_bg;
 
 	BUG_ON(!flex_gd->count || !group_data ||
 	       group_data[0].group != sbi->s_groups_count);
 
 	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
+	meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
 
 	/* This transaction may be extended/restarted along the way */
 	handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);
@@ -452,15 +473,25 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
 	group = group_data[0].group;
 	for (i = 0; i < flex_gd->count; i++, group++) {
 		unsigned long gdblocks;
+		ext4_grpblk_t overhead;
 
 		gdblocks = ext4_bg_num_gdb(sb, group);
 		start = ext4_group_first_block_no(sb, group);
 
-		if (!ext4_bg_has_super(sb, group))
+		if (meta_bg == 0 && !ext4_bg_has_super(sb, group))
 			goto handle_itb;
 
+		if (meta_bg == 1) {
+			ext4_group_t first_group;
+			first_group = ext4_meta_bg_first_group(sb, group);
+			if (first_group != group + 1 &&
+			    first_group != group + EXT4_DESC_PER_BLOCK(sb) - 1)
+				goto handle_itb;
+		}
+
+		block = start + ext4_bg_has_super(sb, group);
 		/* Copy all of the GDT blocks into the backup in this group */
-		for (j = 0, block = start + 1; j < gdblocks; j++, block++) {
+		for (j = 0; j < gdblocks; j++, block++) {
 			struct buffer_head *gdb;
 
 			ext4_debug("update backup group %#04llx\n", block);
@@ -530,11 +561,11 @@ handle_bb:
 			err = PTR_ERR(bh);
 			goto out;
 		}
-		if (ext4_bg_has_super(sb, group)) {
+		overhead = ext4_group_overhead_blocks(sb, group);
+		if (overhead != 0) {
 			ext4_debug("mark backup superblock %#04llx (+0)\n",
 				   start);
-			ext4_set_bits(bh->b_data, 0, gdblocks + reserved_gdb +
-						     1);
+			ext4_set_bits(bh->b_data, 0, overhead);
 		}
 		ext4_mark_bitmap_end(group_data[i].blocks_count,
 				     sb->s_blocksize * 8, bh->b_data);
@@ -831,6 +862,45 @@ exit_bh:
 }
 
 /*
+ * add_new_gdb_meta_bg is the sister of add_new_gdb.
+ */
+static int add_new_gdb_meta_bg(struct super_block *sb,
+			       handle_t *handle, ext4_group_t group) {
+	ext4_fsblk_t gdblock;
+	struct buffer_head *gdb_bh;
+	struct buffer_head **o_group_desc, **n_group_desc;
+	unsigned long gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
+	int err;
+
+	gdblock = ext4_meta_bg_first_block_no(sb, group) +
+		   ext4_bg_has_super(sb, group);
+	gdb_bh = sb_bread(sb, gdblock);
+	if (!gdb_bh)
+		return -EIO;
+	n_group_desc = ext4_kvmalloc((gdb_num + 1) *
+				     sizeof(struct buffer_head *),
+				     GFP_NOFS);
+	if (!n_group_desc) {
+		err = -ENOMEM;
+		ext4_warning(sb, "not enough memory for %lu groups",
+			     gdb_num + 1);
+		return err;
+	}
+
+	o_group_desc = EXT4_SB(sb)->s_group_desc;
+	memcpy(n_group_desc, o_group_desc,
+	       EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
+	n_group_desc[gdb_num] = gdb_bh;
+	EXT4_SB(sb)->s_group_desc = n_group_desc;
+	EXT4_SB(sb)->s_gdb_count++;
+	ext4_kvfree(o_group_desc);
+	err = ext4_journal_get_write_access(handle, gdb_bh);
+	if (unlikely(err))
+		brelse(gdb_bh);
+	return err;
+}
+
+/*
  * Called when we are adding a new group which has a backup copy of each of
  * the GDT blocks (i.e. sparse group) and there are reserved GDT blocks.
  * We need to add these reserved backup GDT blocks to the resize inode, so
@@ -958,16 +1028,16 @@ exit_free:
  * do not copy the full number of backups at this time.  The resize
  * which changed s_groups_count will backup again.
  */
-static void update_backups(struct super_block *sb,
-			   int blk_off, char *data, int size)
+static void update_backups(struct super_block *sb, int blk_off, char *data,
+			   int size, int meta_bg)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	const ext4_group_t last = sbi->s_groups_count;
+	ext4_group_t last;
 	const int bpg = EXT4_BLOCKS_PER_GROUP(sb);
 	unsigned three = 1;
 	unsigned five = 5;
 	unsigned seven = 7;
-	ext4_group_t group;
+	ext4_group_t group = 0;
 	int rest = sb->s_blocksize - size;
 	handle_t *handle;
 	int err = 0, err2;
@@ -981,8 +1051,17 @@ static void update_backups(struct super_block *sb,
 
 	ext4_superblock_csum_set(sb, (struct ext4_super_block *)data);
 
-	while ((group = ext4_list_backups(sb, &three, &five, &seven)) < last) {
+	if (meta_bg == 0) {
+		group = ext4_list_backups(sb, &three, &five, &seven);
+		last = sbi->s_groups_count;
+	} else {
+		group = ext4_meta_bg_first_group(sb, group) + 1;
+		last = (ext4_group_t)(group + EXT4_DESC_PER_BLOCK(sb) - 2);
+	}
+
+	while (group < sbi->s_groups_count) {
 		struct buffer_head *bh;
+		ext4_fsblk_t backup_block;
 
 		/* Out of journal space, and can't get more - abort - so sad */
 		if (ext4_handle_valid(handle) &&
@@ -991,13 +1070,20 @@ static void update_backups(struct super_block *sb,
 		    (err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA)))
 			break;
 
-		bh = sb_getblk(sb, group * bpg + blk_off);
+		if (meta_bg == 0)
+			backup_block = group * bpg + blk_off;
+		else
+			backup_block = (ext4_group_first_block_no(sb, group) +
+					ext4_bg_has_super(sb, group));
+
+		bh = sb_getblk(sb, backup_block);
 		if (!bh) {
 			err = -EIO;
 			break;
 		}
-		ext4_debug("update metadata backup %#04lx\n",
-			  (unsigned long)bh->b_blocknr);
+		ext4_debug("update metadata backup %llu(+%llu)\n",
+			   backup_block, backup_block -
+			   ext4_group_first_block_no(sb, group));
 		if ((err = ext4_journal_get_write_access(handle, bh)))
 			break;
 		lock_buffer(bh);
@@ -1010,6 +1096,13 @@ static void update_backups(struct super_block *sb,
 		if (unlikely(err))
 			ext4_std_error(sb, err);
 		brelse(bh);
+
+		if (meta_bg == 0)
+			group = ext4_list_backups(sb, &three, &five, &seven);
+		else if (group == last)
+			break;
+		else
+			group = last;
 	}
 	if ((err2 = ext4_journal_stop(handle)) && !err)
 		err = err2;
@@ -1052,7 +1145,9 @@ static int ext4_add_new_descs(handle_t *handle, struct super_block *sb,
 	struct ext4_super_block *es = sbi->s_es;
 	struct buffer_head *gdb_bh;
 	int i, gdb_off, gdb_num, err = 0;
+	int meta_bg;
 
+	meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
 	for (i = 0; i < count; i++, group++) {
 		int reserved_gdb = ext4_bg_has_super(sb, group) ?
 			le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
@@ -1072,8 +1167,11 @@ static int ext4_add_new_descs(handle_t *handle, struct super_block *sb,
 
 			if (!err && reserved_gdb && ext4_bg_num_gdb(sb, group))
 				err = reserve_backup_gdb(handle, resize_inode, group);
-		} else
+		} else if (meta_bg != 0) {
+			err = add_new_gdb_meta_bg(sb, handle, group);
+		} else {
 			err = add_new_gdb(handle, resize_inode, group);
+		}
 		if (err)
 			break;
 	}
@@ -1225,7 +1323,7 @@ static void ext4_update_super(struct super_block *sb,
 	}
 
 	reserved_blocks = ext4_r_blocks_count(es) * 100;
-	do_div(reserved_blocks, ext4_blocks_count(es));
+	reserved_blocks = div64_u64(reserved_blocks, ext4_blocks_count(es));
 	reserved_blocks *= blocks_count;
 	do_div(reserved_blocks, 100);
 
@@ -1236,6 +1334,7 @@ static void ext4_update_super(struct super_block *sb,
 	le32_add_cpu(&es->s_free_inodes_count, EXT4_INODES_PER_GROUP(sb) *
 		     flex_gd->count);
 
+	ext4_debug("free blocks count %llu", ext4_free_blocks_count(es));
 	/*
 	 * We need to protect s_groups_count against other CPUs seeing
 	 * inconsistent state in the superblock.
@@ -1270,6 +1369,8 @@ static void ext4_update_super(struct super_block *sb,
 	percpu_counter_add(&sbi->s_freeinodes_counter,
 			   EXT4_INODES_PER_GROUP(sb) * flex_gd->count);
 
+	ext4_debug("free blocks count %llu",
+		   percpu_counter_read(&sbi->s_freeclusters_counter));
 	if (EXT4_HAS_INCOMPAT_FEATURE(sb,
 				      EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
 	    sbi->s_log_groups_per_flex) {
@@ -1361,15 +1462,17 @@ exit_journal:
 		int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
 		int gdb_num_end = ((group + flex_gd->count - 1) /
 				   EXT4_DESC_PER_BLOCK(sb));
+		int meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb,
+				EXT4_FEATURE_INCOMPAT_META_BG);
 
 		update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
-			       sizeof(struct ext4_super_block));
+			       sizeof(struct ext4_super_block), 0);
 		for (; gdb_num <= gdb_num_end; gdb_num++) {
 			struct buffer_head *gdb_bh;
 
 			gdb_bh = sbi->s_group_desc[gdb_num];
 			update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
-				       gdb_bh->b_size);
+				       gdb_bh->b_size, meta_bg);
 		}
 	}
 exit:
@@ -1413,9 +1516,7 @@ static int ext4_setup_next_flex_gd(struct super_block *sb,
 
 		group_data[i].group = group + i;
 		group_data[i].blocks_count = blocks_per_group;
-		overhead = ext4_bg_has_super(sb, group + i) ?
-			   (1 + ext4_bg_num_gdb(sb, group + i) +
-			    le16_to_cpu(es->s_reserved_gdt_blocks)) : 0;
+		overhead = ext4_group_overhead_blocks(sb, group + i);
 		group_data[i].free_blocks_count = blocks_per_group - overhead;
 		if (ext4_has_group_desc_csum(sb))
 			flex_gd->bg_flags[i] = EXT4_BG_BLOCK_UNINIT |
@@ -1563,11 +1664,13 @@ errout:
 		err = err2;
 
 	if (!err) {
+		ext4_fsblk_t first_block;
+		first_block = ext4_group_first_block_no(sb, 0);
 		if (test_opt(sb, DEBUG))
 			printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
 			       "blocks\n", ext4_blocks_count(es));
-		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr, (char *)es,
-			       sizeof(struct ext4_super_block));
+		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr - first_block,
+			       (char *)es, sizeof(struct ext4_super_block), 0);
 	}
 	return err;
 }
@@ -1662,15 +1765,16 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
 	struct buffer_head *bh;
-	struct inode *resize_inode;
-	ext4_fsblk_t o_blocks_count;
-	ext4_group_t o_group;
-	ext4_group_t n_group;
-	ext4_grpblk_t offset, add;
+	struct inode *resize_inode = NULL;
+	ext4_grpblk_t add, offset;
 	unsigned long n_desc_blocks;
 	unsigned long o_desc_blocks;
 	unsigned long desc_blocks;
+	ext4_group_t o_group;
+	ext4_group_t n_group;
+	ext4_fsblk_t o_blocks_count;
 	int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
+	int meta_bg;
 
 	o_blocks_count = ext4_blocks_count(es);
 
@@ -1692,22 +1796,33 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
 
 	n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) /
-			EXT4_DESC_PER_BLOCK(sb);
+			 EXT4_DESC_PER_BLOCK(sb);
 	o_desc_blocks = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
-			EXT4_DESC_PER_BLOCK(sb);
+			 EXT4_DESC_PER_BLOCK(sb);
 	desc_blocks = n_desc_blocks - o_desc_blocks;
 
-	if (desc_blocks &&
-	    (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE) ||
-	     le16_to_cpu(es->s_reserved_gdt_blocks) < desc_blocks)) {
-		ext4_warning(sb, "No reserved GDT blocks, can't resize");
-		return -EPERM;
-	}
+	meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
 
-	resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
-	if (IS_ERR(resize_inode)) {
-		ext4_warning(sb, "Error opening resize inode");
-		return PTR_ERR(resize_inode);
+	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE)) {
+		if (meta_bg) {
+			ext4_error(sb, "resize_inode and meta_bg enabled "
+				   "simultaneously");
+			return -EINVAL;
+		}
+		if (le16_to_cpu(es->s_reserved_gdt_blocks) < desc_blocks) {
+			ext4_warning(sb,
+				     "No reserved GDT blocks, can't resize");
+			return -EPERM;
+		}
+		resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
+		if (IS_ERR(resize_inode)) {
+			ext4_warning(sb, "Error opening resize inode");
+			return PTR_ERR(resize_inode);
+		}
+	} else if (!meta_bg) {
+		ext4_warning(sb, "File system features do not permit "
+			     "online resize");
+		return -EPERM;
 	}
 
 	/* See if the device is actually as big as what was requested */
@@ -1761,8 +1876,8 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 out:
 	if (flex_gd)
 		free_flex_gd(flex_gd);

[PATCH 6/9] ext4: set bg_itable_unused when resizing

[Theodore Ts'o]

Set bg_itable_unused for file systems that have uninit_bg enabled.
This will speed up the first e2fsck run after the file system is
resized.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/resize.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 7adc088..a5be589 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1268,6 +1268,9 @@ static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb,
 		ext4_free_group_clusters_set(sb, gdp,
 					     EXT4_B2C(sbi, group_data->free_blocks_count));
 		ext4_free_inodes_set(sb, gdp, EXT4_INODES_PER_GROUP(sb));
+		if (ext4_has_group_desc_csum(sb))
+			ext4_itable_unused_set(sb, gdp,
+					       EXT4_INODES_PER_GROUP(sb));
 		gdp->bg_flags = cpu_to_le16(*bg_flags);
 		ext4_group_desc_csum_set(sb, group, gdp);
 
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 7/9] ext4: convert file system to meta_bg if needed during resizing

[Theodore Ts'o]

If we have run out of reserved gdt blocks, then clear the resize_inode
feature and enable the meta_bg feature, so that we can continue
resizing the file system seamlessly.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/resize.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 133 insertions(+), 17 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a5be589..5932ab5 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1756,6 +1756,99 @@ int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
 	return err;
 } /* ext4_group_extend */
 
+
+static int num_desc_blocks(struct super_block *sb, ext4_group_t groups)
+{
+	return (groups + EXT4_DESC_PER_BLOCK(sb) - 1) / EXT4_DESC_PER_BLOCK(sb);
+}
+
+/*
+ * Release the resize inode and drop the resize_inode feature if there
+ * are no more reserved gdt blocks, and then convert the file system
+ * to enable meta_bg
+ */
+static int ext4_convert_meta_bg(struct super_block *sb, struct inode *inode)
+{
+	handle_t *handle;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_super_block *es = sbi->s_es;
+	struct ext4_inode_info *ei = 0;
+	ext4_fsblk_t nr;
+	int i, ret, err = 0;
+	int credits = 1;
+
+	ext4_msg(sb, KERN_INFO, "Converting file system to meta_bg");
+	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE)) {
+		if (es->s_reserved_gdt_blocks) {
+			ext4_error(sb, "Unexpected non-zero "
+				   "s_reserved_gdt_blocks");
+			return -EPERM;
+		}
+		if (!inode) {
+			ext4_error(sb, "Unexpected NULL resize_inode");
+			return -EPERM;
+		}
+		ei = EXT4_I(inode);
+
+		/* Do a quick sanity check of the resize inode */
+		if (inode->i_blocks != 1 << (inode->i_blkbits - 9))
+			goto invalid_resize_inode;
+		for (i = 0; i < EXT4_N_BLOCKS; i++) {
+			if (i == EXT4_DIND_BLOCK) {
+				if (ei->i_data[i])
+					continue;
+				else
+					goto invalid_resize_inode;
+			}
+			if (ei->i_data[i])
+				goto invalid_resize_inode;
+		}
+		credits += 3;	/* block bitmap, bg descriptor, resize inode */
+	}
+
+	handle = ext4_journal_start_sb(sb, credits);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	err = ext4_journal_get_write_access(handle, sbi->s_sbh);
+	if (err)
+		goto errout;
+
+	EXT4_CLEAR_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE);
+	EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
+	sbi->s_es->s_first_meta_bg =
+		cpu_to_le32(num_desc_blocks(sb, sbi->s_groups_count));
+
+	err = ext4_handle_dirty_super(handle, sb);
+	if (err) {
+		ext4_std_error(sb, err);
+		goto errout;
+	}
+
+	if (inode) {
+		nr = le32_to_cpu(ei->i_data[EXT4_DIND_BLOCK]);
+		ext4_free_blocks(handle, inode, NULL, nr, 1,
+				 EXT4_FREE_BLOCKS_METADATA |
+				 EXT4_FREE_BLOCKS_FORGET);
+		ei->i_data[EXT4_DIND_BLOCK] = 0;
+		inode->i_blocks = 0;
+
+		err = ext4_mark_inode_dirty(handle, inode);
+		if (err)
+			ext4_std_error(sb, err);
+	}
+
+errout:
+	ret = ext4_journal_stop(handle);
+	if (!err)
+		err = ret;
+	return ret;
+
+invalid_resize_inode:
+	ext4_error(sb, "corrupted/inconsistent resize inode");
+	return -EINVAL;
+}
+
 /*
  * ext4_resize_fs() resizes a fs to new size specified by @n_blocks_count
  *
@@ -1772,13 +1865,14 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	ext4_grpblk_t add, offset;
 	unsigned long n_desc_blocks;
 	unsigned long o_desc_blocks;
-	unsigned long desc_blocks;
 	ext4_group_t o_group;
 	ext4_group_t n_group;
 	ext4_fsblk_t o_blocks_count;
+	ext4_fsblk_t n_blocks_count_retry = 0;
 	int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
 	int meta_bg;
 
+retry:
 	o_blocks_count = ext4_blocks_count(es);
 
 	if (test_opt(sb, DEBUG))
@@ -1798,11 +1892,8 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset);
 	ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
 
-	n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) /
-			 EXT4_DESC_PER_BLOCK(sb);
-	o_desc_blocks = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
-			 EXT4_DESC_PER_BLOCK(sb);
-	desc_blocks = n_desc_blocks - o_desc_blocks;
+	n_desc_blocks = num_desc_blocks(sb, n_group + 1);
+	o_desc_blocks = num_desc_blocks(sb, sbi->s_groups_count);
 
 	meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
 
@@ -1812,20 +1903,37 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 				   "simultaneously");
 			return -EINVAL;
 		}
-		if (le16_to_cpu(es->s_reserved_gdt_blocks) < desc_blocks) {
-			ext4_warning(sb,
-				     "No reserved GDT blocks, can't resize");
-			return -EPERM;
+		if (n_desc_blocks > o_desc_blocks +
+		    le16_to_cpu(es->s_reserved_gdt_blocks)) {
+			n_blocks_count_retry = n_blocks_count;
+			n_desc_blocks = o_desc_blocks +
+				le16_to_cpu(es->s_reserved_gdt_blocks);
+			n_group = n_desc_blocks * EXT4_DESC_PER_BLOCK(sb);
+			n_blocks_count = n_group * EXT4_BLOCKS_PER_GROUP(sb);
+			n_group--; /* set to last group number */
 		}
-		resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
+
+		if (!resize_inode)
+			resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
 		if (IS_ERR(resize_inode)) {
 			ext4_warning(sb, "Error opening resize inode");
 			return PTR_ERR(resize_inode);
 		}
-	} else if (!meta_bg) {
-		ext4_warning(sb, "File system features do not permit "
-			     "online resize");
-		return -EPERM;
+	}
+
+	if ((!resize_inode && !meta_bg) || n_group == o_group) {
+		err = ext4_convert_meta_bg(sb, resize_inode);
+		if (err)
+			goto out;
+		if (resize_inode) {
+			iput(resize_inode);
+			resize_inode = NULL;
+		}
+		if (n_blocks_count_retry) {
+			n_blocks_count = n_blocks_count_retry;
+			n_blocks_count_retry = 0;
+			goto retry;
+		}
 	}
 
 	/* See if the device is actually as big as what was requested */
@@ -1876,13 +1984,21 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 			break;
 	}
 
+	if (!err && n_blocks_count_retry) {
+		n_blocks_count = n_blocks_count_retry;
+		n_blocks_count_retry = 0;
+		free_flex_gd(flex_gd);
+		flex_gd = NULL;
+		goto retry;
+	}
+
 out:
 	if (flex_gd)
 		free_flex_gd(flex_gd);
 	if (resize_inode != NULL)
 		iput(resize_inode);
 	if (test_opt(sb, DEBUG))
-		ext4_msg(sb, KERN_DEBUG, "resized filesystem from %llu "
-		       "upto %llu blocks", o_blocks_count, n_blocks_count);
+		ext4_msg(sb, KERN_DEBUG, "resized filesystem to %llu",
+			 n_blocks_count);
 	return err;
 }
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 8/9] ext4: log a resize update to the console every 10 seconds

[Theodore Ts'o]

For very long online resizes, a periodic update to the console log is
helpful for debugging and for progress reporting.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/resize.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 5932ab5..3c9367b 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1869,6 +1869,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 	ext4_group_t n_group;
 	ext4_fsblk_t o_blocks_count;
 	ext4_fsblk_t n_blocks_count_retry = 0;
+	unsigned long last_update_time = 0;
 	int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
 	int meta_bg;
 
@@ -1977,6 +1978,13 @@ retry:
 	 */
 	while (ext4_setup_next_flex_gd(sb, flex_gd, n_blocks_count,
 					      flexbg_size)) {
+		if (jiffies - last_update_time > HZ * 10) {
+			if (last_update_time)
+				ext4_msg(sb, KERN_INFO,
+					 "resized to %llu blocks",
+					 ext4_blocks_count(es));
+			last_update_time = jiffies;
+		}
 		if (ext4_alloc_group_tables(sb, flex_gd, flexbg_size) != 0)
 			break;
 		err = ext4_flex_group_add(sb, resize_inode, flex_gd);
-- 
1.7.12.rc0.22.gcdd159b

[PATCH 9/9] ext4: advertise the fact that the kernel supports meta_bg resizing

[Theodore Ts'o]

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/super.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b8de488..eb7722a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2585,10 +2585,12 @@ static struct attribute *ext4_attrs[] = {
 /* Features this copy of ext4 supports */
 EXT4_INFO_ATTR(lazy_itable_init);
 EXT4_INFO_ATTR(batched_discard);
+EXT4_INFO_ATTR(meta_bg_resize);
 
 static struct attribute *ext4_feat_attrs[] = {
 	ATTR_LIST(lazy_itable_init),
 	ATTR_LIST(batched_discard),
+	ATTR_LIST(meta_bg_resize),
 	NULL,
 };
 
-- 
1.7.12.rc0.22.gcdd159b