[PATCH 1/3] bcachefs: BCH_FEATURE_no_alloc_info

[PATCH 1/3] bcachefs: BCH_FEATURE_no_alloc_info

[Kent Overstreet]

If a filesystem is going to only be used read-only, and will be a
deployable image, we can strip out alloc info for a substantial
reduction in metadata size - around half, due to backpointers.

Alloc info will be regenerated on first read-write mount.

Remounting RW is disallowed for now, since we don't yet have
check_allocations running in RW mode.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/bcachefs_format.h       |  3 ++-
 fs/bcachefs/errcode.h               |  1 +
 fs/bcachefs/recovery.c              | 28 ++++++++++++++++++++++------
 fs/bcachefs/recovery.h              |  1 +
 fs/bcachefs/recovery_passes.c       | 14 +++++++++++++-
 fs/bcachefs/recovery_passes_types.h | 18 ++++++++++--------
 fs/bcachefs/sb-members.c            |  6 ++++++
 fs/bcachefs/super.c                 |  6 ++++++
 8 files changed, 61 insertions(+), 16 deletions(-)

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index e6203665f230..7e2debc40045 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -918,7 +918,8 @@ static inline void SET_BCH_SB_BACKGROUND_COMPRESSION_TYPE(struct bch_sb *sb, __u
 	x(alloc_v2,			17)	\
 	x(extents_across_btree_nodes,	18)	\
 	x(incompat_version_field,	19)	\
-	x(casefolding,			20)
+	x(casefolding,			20)	\
+	x(no_alloc_info,		21)
 
 #define BCH_SB_FEATURES_ALWAYS				\
 	(BIT_ULL(BCH_FEATURE_new_extent_overwrite)|	\
diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index 4a040085454c..e54c8264e7e1 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -221,6 +221,7 @@
 	x(EROFS,			erofs_unfixed_errors)			\
 	x(EROFS,			erofs_norecovery)			\
 	x(EROFS,			erofs_nochanges)			\
+	x(EROFS,			erofs_no_alloc_info)			\
 	x(EROFS,			insufficient_devices)			\
 	x(0,				operation_blocked)			\
 	x(BCH_ERR_operation_blocked,	btree_cache_cannibalize_lock_blocked)	\
diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
index 58ee1ebdcbaa..fbe2e6406f53 100644
--- a/fs/bcachefs/recovery.c
+++ b/fs/bcachefs/recovery.c
@@ -32,7 +32,6 @@
 #include <linux/sort.h>
 #include <linux/stat.h>
 
-
 int bch2_btree_lost_data(struct bch_fs *c, enum btree_id btree)
 {
 	u64 b = BIT_ULL(btree);
@@ -113,11 +112,8 @@ static void kill_btree(struct bch_fs *c, enum btree_id btree)
 }
 
 /* for -o reconstruct_alloc: */
-static void bch2_reconstruct_alloc(struct bch_fs *c)
+void bch2_reconstruct_alloc(struct bch_fs *c)
 {
-	bch2_journal_log_msg(c, "dropping alloc info");
-	bch_info(c, "dropping and reconstructing all alloc info");
-
 	mutex_lock(&c->sb_lock);
 	struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext);
 
@@ -159,6 +155,8 @@ static void bch2_reconstruct_alloc(struct bch_fs *c)
 
 	c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0]));
 
+	c->disk_sb.sb->features[0] &= ~cpu_to_le64(BIT_ULL(BCH_FEATURE_no_alloc_info));
+
 	bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);
 
@@ -888,8 +886,26 @@ int bch2_fs_recovery(struct bch_fs *c)
 	if (ret)
 		goto err;
 
-	if (c->opts.reconstruct_alloc)
+	if (!c->opts.read_only &&
+	    (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info))) {
+		bch_info(c, "mounting a filesystem with no alloc info read-write; will recreate");
+
 		bch2_reconstruct_alloc(c);
+	} else if (c->opts.reconstruct_alloc) {
+		bch2_journal_log_msg(c, "dropping alloc info");
+		bch_info(c, "dropping and reconstructing all alloc info");
+
+		bch2_reconstruct_alloc(c);
+	}
+
+	if (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)) {
+		/* We can't go RW to fix errors without alloc info */
+		if (c->opts.fix_errors == FSCK_FIX_yes ||
+		    c->opts.fix_errors == FSCK_FIX_ask)
+			c->opts.fix_errors = FSCK_FIX_no;
+		if (c->opts.errors == BCH_ON_ERROR_fix_safe)
+			c->opts.errors = BCH_ON_ERROR_continue;
+	}
 
 	/*
 	 * After an unclean shutdown, skip then next few journal sequence
diff --git a/fs/bcachefs/recovery.h b/fs/bcachefs/recovery.h
index b0d55754b21b..d858ba674eaa 100644
--- a/fs/bcachefs/recovery.h
+++ b/fs/bcachefs/recovery.h
@@ -3,6 +3,7 @@
 #define _BCACHEFS_RECOVERY_H
 
 int bch2_btree_lost_data(struct bch_fs *, enum btree_id);
+void bch2_reconstruct_alloc(struct bch_fs *);
 
 int bch2_journal_replay(struct bch_fs *);
 
diff --git a/fs/bcachefs/recovery_passes.c b/fs/bcachefs/recovery_passes.c
index 92e431af9ac3..7a6444088aa6 100644
--- a/fs/bcachefs/recovery_passes.c
+++ b/fs/bcachefs/recovery_passes.c
@@ -46,8 +46,18 @@ static int bch2_set_may_go_rw(struct bch_fs *c)
 
 	set_bit(BCH_FS_may_go_rw, &c->flags);
 
-	if (keys->nr || !c->opts.read_only || c->opts.fsck || !c->sb.clean || c->opts.recovery_passes)
+	if (keys->nr ||
+	    !c->opts.read_only ||
+	    !c->sb.clean ||
+	    c->opts.recovery_passes ||
+	    (c->opts.fsck && !(c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)))) {
+		if (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)) {
+			bch_info(c, "mounting a filesystem with no alloc info read-write; will recreate");
+			bch2_reconstruct_alloc(c);
+		}
+
 		return bch2_fs_read_write_early(c);
+	}
 	return 0;
 }
 
@@ -239,6 +249,8 @@ static bool should_run_recovery_pass(struct bch_fs *c, enum bch_recovery_pass pa
 {
 	struct recovery_pass_fn *p = recovery_pass_fns + pass;
 
+	if ((p->when & PASS_ALLOC) && (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)))
+		return false;
 	if (c->opts.recovery_passes_exclude & BIT_ULL(pass))
 		return false;
 	if (c->opts.recovery_passes & BIT_ULL(pass))
diff --git a/fs/bcachefs/recovery_passes_types.h b/fs/bcachefs/recovery_passes_types.h
index 4671ccf2d560..f9d565bb50dd 100644
--- a/fs/bcachefs/recovery_passes_types.h
+++ b/fs/bcachefs/recovery_passes_types.h
@@ -7,6 +7,8 @@
 #define PASS_UNCLEAN		BIT(2)
 #define PASS_ALWAYS		BIT(3)
 #define PASS_ONLINE		BIT(4)
+#define PASS_ALLOC		BIT(5)
+#define PASS_FSCK_ALLOC		(PASS_FSCK|PASS_ALLOC)
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 #define PASS_FSCK_DEBUG		BIT(1)
@@ -27,17 +29,17 @@
 	x(stripes_read,				 1, 0)					\
 	x(initialize_subvolumes,		 2, 0)					\
 	x(snapshots_read,			 3, PASS_ALWAYS)			\
-	x(check_allocations,			 5, PASS_FSCK)				\
-	x(trans_mark_dev_sbs,			 6, PASS_ALWAYS|PASS_SILENT)		\
-	x(fs_journal_alloc,			 7, PASS_ALWAYS|PASS_SILENT)		\
+	x(check_allocations,			 5, PASS_FSCK_ALLOC)			\
+	x(trans_mark_dev_sbs,			 6, PASS_ALWAYS|PASS_SILENT|PASS_ALLOC)	\
+	x(fs_journal_alloc,			 7, PASS_ALWAYS|PASS_SILENT|PASS_ALLOC)	\
 	x(set_may_go_rw,			 8, PASS_ALWAYS|PASS_SILENT)		\
 	x(journal_replay,			 9, PASS_ALWAYS)			\
-	x(check_alloc_info,			10, PASS_ONLINE|PASS_FSCK)		\
-	x(check_lrus,				11, PASS_ONLINE|PASS_FSCK)		\
-	x(check_btree_backpointers,		12, PASS_ONLINE|PASS_FSCK)		\
+	x(check_alloc_info,			10, PASS_ONLINE|PASS_FSCK_ALLOC)	\
+	x(check_lrus,				11, PASS_ONLINE|PASS_FSCK_ALLOC)	\
+	x(check_btree_backpointers,		12, PASS_ONLINE|PASS_FSCK_ALLOC)	\
 	x(check_backpointers_to_extents,	13, PASS_ONLINE|PASS_FSCK_DEBUG)	\
-	x(check_extents_to_backpointers,	14, PASS_ONLINE|PASS_FSCK)		\
-	x(check_alloc_to_lru_refs,		15, PASS_ONLINE|PASS_FSCK)		\
+	x(check_extents_to_backpointers,	14, PASS_ONLINE|PASS_FSCK_ALLOC)	\
+	x(check_alloc_to_lru_refs,		15, PASS_ONLINE|PASS_FSCK_ALLOC)	\
 	x(fs_freespace_init,			16, PASS_ALWAYS|PASS_SILENT)		\
 	x(bucket_gens_init,			17, 0)					\
 	x(reconstruct_snapshots,		38, 0)					\
diff --git a/fs/bcachefs/sb-members.c b/fs/bcachefs/sb-members.c
index cdc4258c3c21..9a82ed3f18f5 100644
--- a/fs/bcachefs/sb-members.c
+++ b/fs/bcachefs/sb-members.c
@@ -188,6 +188,12 @@ static int validate_member(struct printbuf *err,
 		return -BCH_ERR_invalid_sb_members;
 	}
 
+	if (BCH_MEMBER_FREESPACE_INITIALIZED(&m) &&
+	    sb->features[0] & BIT_ULL(BCH_FEATURE_no_alloc_info)) {
+		prt_printf(err, "device %u: freespace initialized but fs has no alloc info", i);
+		return -BCH_ERR_invalid_sb_members;
+	}
+
 	return 0;
 }
 
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 2d244deb07a8..797601756af1 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -464,6 +464,9 @@ static int __bch2_fs_read_write(struct bch_fs *c, bool early)
 
 	BUG_ON(!test_bit(BCH_FS_may_go_rw, &c->flags));
 
+	if (WARN_ON(c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info)))
+		return -BCH_ERR_erofs_no_alloc_info;
+
 	if (test_bit(BCH_FS_initial_gc_unfixed, &c->flags)) {
 		bch_err(c, "cannot go rw, unfixed btree errors");
 		return -BCH_ERR_erofs_unfixed_errors;
@@ -550,6 +553,9 @@ int bch2_fs_read_write(struct bch_fs *c)
 	if (c->opts.nochanges)
 		return -BCH_ERR_erofs_nochanges;
 
+	if (c->sb.features & BIT_ULL(BCH_FEATURE_no_alloc_info))
+		return -BCH_ERR_erofs_no_alloc_info;
+
 	return __bch2_fs_read_write(c, false);
 }
 
-- 
2.49.0

[PATCH 2/3] bcachefs: BCH_FEATURE_small_image

[Kent Overstreet]

We can't go RW if it's an image file that hasn't been resized.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/bcachefs_format.h | 3 ++-
 fs/bcachefs/errcode.h         | 1 +
 fs/bcachefs/journal.c         | 9 ++++++++-
 fs/bcachefs/super.c           | 5 +++++
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index 7e2debc40045..aa57f4708232 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -919,7 +919,8 @@ static inline void SET_BCH_SB_BACKGROUND_COMPRESSION_TYPE(struct bch_sb *sb, __u
 	x(extents_across_btree_nodes,	18)	\
 	x(incompat_version_field,	19)	\
 	x(casefolding,			20)	\
-	x(no_alloc_info,		21)
+	x(no_alloc_info,		21)	\
+	x(small_image,			22)
 
 #define BCH_SB_FEATURES_ALWAYS				\
 	(BIT_ULL(BCH_FEATURE_new_extent_overwrite)|	\
diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index e54c8264e7e1..996cdf62dad9 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -222,6 +222,7 @@
 	x(EROFS,			erofs_norecovery)			\
 	x(EROFS,			erofs_nochanges)			\
 	x(EROFS,			erofs_no_alloc_info)			\
+	x(EROFS,			erofs_filesystem_full)			\
 	x(EROFS,			insufficient_devices)			\
 	x(0,				operation_blocked)			\
 	x(BCH_ERR_operation_blocked,	btree_cache_cannibalize_lock_blocked)	\
diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 23f37dbfaba9..898f61250b5d 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -1278,9 +1278,16 @@ int bch2_set_nr_journal_buckets(struct bch_fs *c, struct bch_dev *ca,
 
 int bch2_dev_journal_alloc(struct bch_dev *ca, bool new_fs)
 {
+	struct bch_fs *c = ca->fs;
+
 	if (!(ca->mi.data_allowed & BIT(BCH_DATA_journal)))
 		return 0;
 
+	if (c->sb.features & BIT_ULL(BCH_FEATURE_small_image)) {
+		bch_err(c, "cannot allocate journal, filesystem is an unresized image file");
+		return -BCH_ERR_erofs_filesystem_full;
+	}
+
 	unsigned nr;
 	int ret;
 
@@ -1301,7 +1308,7 @@ int bch2_dev_journal_alloc(struct bch_dev *ca, bool new_fs)
 		     min(1 << 13,
 			 (1 << 24) / ca->mi.bucket_size));
 
-	ret = bch2_set_nr_journal_buckets_loop(ca->fs, ca, nr, new_fs);
+	ret = bch2_set_nr_journal_buckets_loop(c, ca, nr, new_fs);
 err:
 	bch_err_fn(ca, ret);
 	return ret;
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 797601756af1..29c4204d2e50 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -472,6 +472,11 @@ static int __bch2_fs_read_write(struct bch_fs *c, bool early)
 		return -BCH_ERR_erofs_unfixed_errors;
 	}
 
+	if (c->sb.features & BIT_ULL(BCH_FEATURE_small_image)) {
+		bch_err(c, "cannot go rw, filesystem is an unresized image file");
+		return -BCH_ERR_erofs_filesystem_full;
+	}
+
 	if (test_bit(BCH_FS_rw, &c->flags))
 		return 0;
 
-- 
2.49.0

[PATCH 3/3] bcachefs: BCH_MEMBER_RESIZE_ON_MOUNT

[Kent Overstreet]

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/recovery.c          |  4 ++
 fs/bcachefs/sb-members.c        |  1 +
 fs/bcachefs/sb-members.h        |  1 +
 fs/bcachefs/sb-members_format.h |  2 +
 fs/bcachefs/sb-members_types.h  |  1 +
 fs/bcachefs/super.c             | 67 +++++++++++++++++++++++++++++----
 fs/bcachefs/super.h             |  1 +
 7 files changed, 70 insertions(+), 7 deletions(-)

diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
index fbe2e6406f53..f7b4b659069e 100644
--- a/fs/bcachefs/recovery.c
+++ b/fs/bcachefs/recovery.c
@@ -949,6 +949,10 @@ int bch2_fs_recovery(struct bch_fs *c)
 
 	ret = bch2_sb_set_upgrade_extra(c);
 
+	ret = bch2_fs_resize_on_mount(c);
+	if (ret)
+		goto err;
+
 	ret = bch2_run_recovery_passes(c);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/sb-members.c b/fs/bcachefs/sb-members.c
index 9a82ed3f18f5..b2f9cb2d2b6b 100644
--- a/fs/bcachefs/sb-members.c
+++ b/fs/bcachefs/sb-members.c
@@ -292,6 +292,7 @@ static void member_to_text(struct printbuf *out,
 
 	prt_printf(out, "Discard:\t%llu\n", BCH_MEMBER_DISCARD(&m));
 	prt_printf(out, "Freespace initialized:\t%llu\n", BCH_MEMBER_FREESPACE_INITIALIZED(&m));
+	prt_printf(out, "Resize on mount:\t%llu\n", BCH_MEMBER_RESIZE_ON_MOUNT(&m));
 
 	printbuf_indent_sub(out, 2);
 }
diff --git a/fs/bcachefs/sb-members.h b/fs/bcachefs/sb-members.h
index 99d15e54726b..e2a8d03a1fa1 100644
--- a/fs/bcachefs/sb-members.h
+++ b/fs/bcachefs/sb-members.h
@@ -350,6 +350,7 @@ static inline struct bch_member_cpu bch2_mi_to_cpu(struct bch_member *mi)
 			? BCH_MEMBER_DURABILITY(mi) - 1
 			: 1,
 		.freespace_initialized = BCH_MEMBER_FREESPACE_INITIALIZED(mi),
+		.resize_on_mount	= BCH_MEMBER_RESIZE_ON_MOUNT(mi),
 		.valid		= bch2_member_alive(mi),
 		.btree_bitmap_shift	= mi->btree_bitmap_shift,
 		.btree_allocated_bitmap = le64_to_cpu(mi->btree_allocated_bitmap),
diff --git a/fs/bcachefs/sb-members_format.h b/fs/bcachefs/sb-members_format.h
index 3affec823b3f..472218a59102 100644
--- a/fs/bcachefs/sb-members_format.h
+++ b/fs/bcachefs/sb-members_format.h
@@ -88,6 +88,8 @@ LE64_BITMASK(BCH_MEMBER_GROUP,		struct bch_member, flags, 20, 28)
 LE64_BITMASK(BCH_MEMBER_DURABILITY,	struct bch_member, flags, 28, 30)
 LE64_BITMASK(BCH_MEMBER_FREESPACE_INITIALIZED,
 					struct bch_member, flags, 30, 31)
+LE64_BITMASK(BCH_MEMBER_RESIZE_ON_MOUNT,
+					struct bch_member, flags, 31, 32)
 
 #if 0
 LE64_BITMASK(BCH_MEMBER_NR_READ_ERRORS,	struct bch_member, flags[1], 0,  20);
diff --git a/fs/bcachefs/sb-members_types.h b/fs/bcachefs/sb-members_types.h
index c0eda888fe39..d6443e186872 100644
--- a/fs/bcachefs/sb-members_types.h
+++ b/fs/bcachefs/sb-members_types.h
@@ -13,6 +13,7 @@ struct bch_member_cpu {
 	u8			data_allowed;
 	u8			durability;
 	u8			freespace_initialized;
+	u8			resize_on_mount;
 	u8			valid;
 	u8			btree_bitmap_shift;
 	u64			btree_allocated_bitmap;
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 29c4204d2e50..3fa4706cfffd 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -1110,6 +1110,7 @@ int bch2_fs_start(struct bch_fs *c)
 	for_each_online_member(c, ca)
 		bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx)->last_mount = cpu_to_le64(now);
 
+	bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);
 
 	for_each_rw_member(c, ca)
@@ -2045,6 +2046,18 @@ int bch2_dev_offline(struct bch_fs *c, struct bch_dev *ca, int flags)
 	return 0;
 }
 
+static int __bch2_dev_resize_alloc(struct bch_dev *ca, u64 old_nbuckets, u64 new_nbuckets)
+{
+	struct bch_fs *c = ca->fs;
+	u64 v[3] = { new_nbuckets - old_nbuckets, 0, 0 };
+
+	return bch2_trans_commit_do(ca->fs, NULL, NULL, 0,
+			bch2_disk_accounting_mod2(trans, false, v, dev_data_type,
+						  .dev = ca->dev_idx,
+						  .data_type = BCH_DATA_free)) ?:
+		bch2_dev_freespace_init(c, ca, old_nbuckets, new_nbuckets);
+}
+
 int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 {
 	struct bch_member *m;
@@ -2092,13 +2105,7 @@ int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 	mutex_unlock(&c->sb_lock);
 
 	if (ca->mi.freespace_initialized) {
-		u64 v[3] = { nbuckets - old_nbuckets, 0, 0 };
-
-		ret   = bch2_trans_commit_do(ca->fs, NULL, NULL, 0,
-				bch2_disk_accounting_mod2(trans, false, v, dev_data_type,
-							  .dev = ca->dev_idx,
-							  .data_type = BCH_DATA_free)) ?:
-			bch2_dev_freespace_init(c, ca, old_nbuckets, nbuckets);
+		ret = __bch2_dev_resize_alloc(ca, old_nbuckets, nbuckets);
 		if (ret)
 			goto err;
 	}
@@ -2109,6 +2116,52 @@ int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 	return ret;
 }
 
+int bch2_fs_resize_on_mount(struct bch_fs *c)
+{
+	down_write(&c->state_lock);
+
+	for_each_online_member(c, ca) {
+		u64 old_nbuckets = ca->mi.nbuckets;
+		u64 new_nbuckets = div64_u64(get_capacity(ca->disk_sb.bdev->bd_disk),
+					 ca->mi.bucket_size);
+
+		if (ca->mi.resize_on_mount &&
+		    new_nbuckets > ca->mi.nbuckets) {
+			bch_info(ca, "resizing to size %llu", new_nbuckets * ca->mi.bucket_size);
+			int ret = bch2_dev_buckets_resize(c, ca, new_nbuckets);
+			bch_err_fn(ca, ret);
+			if (ret) {
+				percpu_ref_put(&ca->io_ref[READ]);
+				up_write(&c->state_lock);
+				return ret;
+			}
+
+			mutex_lock(&c->sb_lock);
+			struct bch_member *m =
+				bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
+			m->nbuckets = cpu_to_le64(new_nbuckets);
+			SET_BCH_MEMBER_RESIZE_ON_MOUNT(m, false);
+
+			c->disk_sb.sb->features[0] &= ~BIT_ULL(BCH_FEATURE_small_image);
+			bch2_write_super(c);
+			mutex_unlock(&c->sb_lock);
+
+			if (ca->mi.freespace_initialized) {
+				ret = __bch2_dev_resize_alloc(ca, old_nbuckets, new_nbuckets);
+				if (ret) {
+					percpu_ref_put(&ca->io_ref[READ]);
+					up_write(&c->state_lock);
+					return ret;
+				}
+			}
+		}
+	}
+
+	bch2_recalc_capacity(c);
+	up_write(&c->state_lock);
+	return 0;
+}
+
 /* return with ref on ca->ref: */
 struct bch_dev *bch2_dev_lookup(struct bch_fs *c, const char *name)
 {
diff --git a/fs/bcachefs/super.h b/fs/bcachefs/super.h
index 23533bce5709..502d6c57ebb2 100644
--- a/fs/bcachefs/super.h
+++ b/fs/bcachefs/super.h
@@ -26,6 +26,7 @@ int bch2_dev_add(struct bch_fs *, const char *);
 int bch2_dev_online(struct bch_fs *, const char *);
 int bch2_dev_offline(struct bch_fs *, struct bch_dev *, int);
 int bch2_dev_resize(struct bch_fs *, struct bch_dev *, u64);
+int bch2_fs_resize_on_mount(struct bch_fs *);
 struct bch_dev *bch2_dev_lookup(struct bch_fs *, const char *);
 
 bool bch2_fs_emergency_read_only(struct bch_fs *);
-- 
2.49.0