Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Daniel Rosenberg <drosen@google.com>
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>,
        Jonathan Corbet <corbet@lwn.net>,
        linux-f2fs-devel@lists.sourceforge.net
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        kernel-team@android.com, Daniel Rosenberg <drosen@google.com>
Subject: [PATCH 1/1] f2fs: checkpoint disabling
Date:   Wed, 11 Jul 2018 18:53:47 -0700
Message-Id: <20180712015347.55992-1-drosen@google.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This adds a lightweight non-persistent snapshotting scheme to f2fs.

To use, mount with the option checkpoint=disable, and to return to
normal operation, remount with checkpoint=enable. If the filesystem
is shut down before remounting with checkpoint=enable, it will revert
back to its apparent state when it was first mounted with
checkpoint=disable. This is useful for situations where you wish to be
able to roll back the state of the disk in case of some critical
failure.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---

This probably needs some work in the mount/remount areas to ensure it
plays nicely with all combinations of other options.
I'm also unsure how it should interact with statfs.

It currently handles accounting for free space in checkpoint disabled
mode by setting up addition tracking for free data blocks, node blocks,
and segments. These are used in inc_valid_block_cnt and inc_valid_node_cnt
to track what the state will be once the blocks are actually allocated.
We choose new current segments in SSR mode first to avoid the edge case
where the disk is not yet full, but we only have dirty segments remaining
that happen to not be of the right type. We also agressively add segments
to the dirty list instead of pre-free when it is possible to reuse them to
allow us to continue without a checkpoint as long as possible.

 Documentation/filesystems/f2fs.txt |   5 ++
 fs/f2fs/data.c                     |  21 ++++++
 fs/f2fs/f2fs.h                     |  63 +++++++++++++++-
 fs/f2fs/file.c                     |  18 +++++
 fs/f2fs/gc.c                       |   4 +
 fs/f2fs/segment.c                  |  96 +++++++++++-------------
 fs/f2fs/segment.h                  |  66 +++++++++++++++++
 fs/f2fs/super.c                    | 115 +++++++++++++++++++++++++++--
 8 files changed, 326 insertions(+), 62 deletions(-)

diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 69f8de9957397..a026b353a99d4 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -193,6 +193,11 @@ fsync_mode=%s          Control the policy of fsync. Currently supports "posix",
                        non-atomic files likewise "nobarrier" mount option.
 test_dummy_encryption  Enable dummy encryption, which provides a fake fscrypt
                        context. The fake fscrypt context is used by xfstests.
+checkpoint=%s          Set to "disable" to turn off checkpointing. Set to "enable"
+                       to reenable checkpointing. Is enabled by default. While
+                       disabled, any unmounting or unexpected shutdowns will cause
+                       the filesystem contents to appear as they did when the
+                       filesystem was mounted with that option.
 
 ================================================================================
 DEBUGFS ENTRIES
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 83d4cff445f53..b3fa713fd42bf 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1654,9 +1654,20 @@ bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
 bool f2fs_should_update_outplace(struct inode *inode, struct f2fs_io_info *fio)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct seg_entry *se;
+	unsigned int segno, offset;
 
 	if (test_opt(sbi, LFS))
 		return true;
+	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+		if (fio->old_blkaddr == NULL_ADDR)
+			return true;
+		segno = GET_SEGNO(sbi, fio->old_blkaddr);
+		se = get_seg_entry(sbi, segno);
+		offset = GET_BLKOFF_FROM_SEG0(sbi, fio->old_blkaddr);
+		if (f2fs_test_bit(offset, se->ckpt_valid_map))
+			return true;
+	}
 	if (S_ISDIR(inode->i_mode))
 		return true;
 	if (f2fs_is_atomic_file(inode))
@@ -1684,9 +1695,12 @@ int f2fs_do_write_data_page(struct f2fs_io_info *fio)
 {
 	struct page *page = fio->page;
 	struct inode *inode = page->mapping->host;
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct dnode_of_data dn;
 	struct extent_info ei = {0,0,0};
 	bool ipu_force = false;
+	bool need_tmp_grab = test_opt(sbi, DISABLE_CHECKPOINT);
+	blkcnt_t tmp_block = 1;
 	int err = 0;
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
@@ -1750,6 +1764,11 @@ int f2fs_do_write_data_page(struct f2fs_io_info *fio)
 	if (err)
 		goto out_writepage;
 
+	if (need_tmp_grab) {
+		err = inc_valid_block_count(sbi, dn.inode, &tmp_block);
+		if (err)
+			goto out_writepage;
+	}
 	set_page_writeback(page);
 	ClearPageError(page);
 
@@ -1759,6 +1778,8 @@ int f2fs_do_write_data_page(struct f2fs_io_info *fio)
 	set_inode_flag(inode, FI_APPEND_WRITE);
 	if (page->index == 0)
 		set_inode_flag(inode, FI_FIRST_BLOCK_WRITTEN);
+	if (need_tmp_grab)
+		dec_valid_block_count(sbi, dn.inode, tmp_block);
 out_writepage:
 	f2fs_put_dnode(&dn);
 out:
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index fe80eb637075c..024b6b971e214 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -97,6 +97,7 @@ extern char *fault_name[FAULT_MAX];
 #define F2FS_MOUNT_QUOTA		0x00400000
 #define F2FS_MOUNT_INLINE_XATTR_SIZE	0x00800000
 #define F2FS_MOUNT_RESERVE_ROOT		0x01000000
+#define F2FS_MOUNT_DISABLE_CHECKPOINT	0x02000000
 
 #define F2FS_OPTION(sbi)	((sbi)->mount_opt)
 #define clear_opt(sbi, option)	(F2FS_OPTION(sbi).opt &= ~F2FS_MOUNT_##option)
@@ -175,6 +176,7 @@ enum {
 #define	CP_RECOVERY	0x00000008
 #define	CP_DISCARD	0x00000010
 #define CP_TRIMMED	0x00000020
+#define CP_PAUSE	0x00000040
 
 #define MAX_DISCARD_BLOCKS(sbi)		BLKS_PER_SEC(sbi)
 #define DEF_MAX_DISCARD_REQUEST		8	/* issue 8 discards per round */
@@ -1067,6 +1069,7 @@ enum {
 	SBI_NEED_SB_WRITE,			/* need to recover superblock */
 	SBI_NEED_CP,				/* need to checkpoint */
 	SBI_IS_SHUTDOWN,			/* shutdown by ioctl */
+	SBI_CP_DISABLED,			/* CP was disabled last mount */
 };
 
 enum {
@@ -1192,6 +1195,12 @@ struct f2fs_sb_info {
 	block_t reserved_blocks;		/* configurable reserved blocks */
 	block_t current_reserved_blocks;	/* current reserved blocks */
 
+	/* Additional tracking for no checkpoint mode */
+	block_t unusable_block_count;		/* # of blocks saved by last cp */
+	block_t free_ssr_data_block;
+	block_t free_ssr_node_block;
+	block_t free_segments;
+
 	unsigned int nquota_files;		/* # of quota sysfile */
 
 	u32 s_next_generation;			/* for NFS support */
@@ -1643,7 +1652,7 @@ static inline void f2fs_i_blocks_write(struct inode *, block_t, bool, bool);
 static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
 				 struct inode *inode, blkcnt_t *count)
 {
-	blkcnt_t diff = 0, release = 0;
+	blkcnt_t diff = 0, release = 0, seg_diff = 0, seg_rel = 0;
 	block_t avail_user_block_count;
 	int ret;
 
@@ -1671,6 +1680,8 @@ static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
 
 	if (!__allow_reserved_blocks(sbi, inode, true))
 		avail_user_block_count -= F2FS_OPTION(sbi).root_reserved_blocks;
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		avail_user_block_count -= sbi->unusable_block_count;
 
 	if (unlikely(sbi->total_valid_block_count > avail_user_block_count)) {
 		diff = sbi->total_valid_block_count - avail_user_block_count;
@@ -1681,18 +1692,51 @@ static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
 		sbi->total_valid_block_count -= diff;
 		if (!*count) {
 			spin_unlock(&sbi->stat_lock);
-			percpu_counter_sub(&sbi->alloc_valid_block_count, diff);
 			goto enospc;
 		}
 	}
+	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+		if (unlikely(*count > sbi->free_ssr_data_block)) {
+			/* We'll need to pull from free. */
+			blkcnt_t needed = *count - sbi->free_ssr_data_block;
+			blkcnt_t new_segs = ((needed - 1) >>
+						sbi->log_blocks_per_seg) + 1;
+
+			/* Check if we have enough free */
+			if (unlikely(new_segs > sbi->free_segments)) {
+				seg_diff = new_segs - sbi->free_segments;
+
+				seg_rel = ((needed - 1) %
+						sbi->log_blocks_per_seg) + 1;
+				seg_rel += (seg_diff - 1) <<
+							sbi->log_blocks_per_seg;
+				new_segs -= seg_diff;
+				*count -= seg_rel;
+				release += seg_rel;
+				if (!*count) {
+					spin_unlock(&sbi->stat_lock);
+					goto enospc;
+				}
+			}
+
+			sbi->free_segments -= new_segs;
+			sbi->free_ssr_data_block += new_segs <<
+							sbi->log_blocks_per_seg;
+
+		}
+		sbi->free_ssr_data_block -= *count;
+	}
 	spin_unlock(&sbi->stat_lock);
 
-	if (unlikely(release))
+	if (unlikely(release)) {
+		percpu_counter_sub(&sbi->alloc_valid_block_count, release);
 		dquot_release_reservation_block(inode, release);
+	}
 	f2fs_i_blocks_write(inode, *count, true, true);
 	return 0;
 
 enospc:
+	percpu_counter_sub(&sbi->alloc_valid_block_count, release);
 	dquot_release_reservation_block(inode, release);
 	return -ENOSPC;
 }
@@ -1878,6 +1922,8 @@ static inline int inc_valid_node_count(struct f2fs_sb_info *sbi,
 
 	if (!__allow_reserved_blocks(sbi, inode, false))
 		valid_block_count += F2FS_OPTION(sbi).root_reserved_blocks;
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		valid_block_count += sbi->unusable_block_count;
 
 	if (unlikely(valid_block_count > sbi->user_block_count)) {
 		spin_unlock(&sbi->stat_lock);
@@ -1890,6 +1936,17 @@ static inline int inc_valid_node_count(struct f2fs_sb_info *sbi,
 		goto enospc;
 	}
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+		if (unlikely(!sbi->free_ssr_node_block)) {
+			if (unlikely(!sbi->free_segments)) {
+				spin_unlock(&sbi->stat_lock);
+				goto enospc;
+			}
+			sbi->free_segments--;
+		}
+		sbi->free_ssr_node_block--;
+	}
+
 	sbi->total_valid_node_count++;
 	sbi->total_valid_block_count++;
 	spin_unlock(&sbi->stat_lock);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 8af6683e022be..1f9a8119e17da 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -150,6 +150,9 @@ static inline enum cp_reason_type need_do_checkpoint(struct inode *inode)
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	enum cp_reason_type cp_reason = CP_NO_NEEDED;
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return CP_NO_NEEDED;
+
 	if (!S_ISREG(inode->i_mode))
 		cp_reason = CP_NON_REGULAR;
 	else if (inode->i_nlink != 1)
@@ -2046,6 +2049,9 @@ static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
 	if (f2fs_readonly(sbi->sb))
 		return -EROFS;
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return -EINVAL;
+
 	ret = mnt_want_write_file(filp);
 	if (ret)
 		return ret;
@@ -2088,6 +2094,9 @@ static int f2fs_ioc_gc_range(struct file *filp, unsigned long arg)
 		return -EINVAL;
 	}
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return -EINVAL;
+
 	ret = mnt_want_write_file(filp);
 	if (ret)
 		return ret;
@@ -2123,6 +2132,12 @@ static int f2fs_ioc_f2fs_write_checkpoint(struct file *filp, unsigned long arg)
 	if (f2fs_readonly(sbi->sb))
 		return -EROFS;
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
+		f2fs_msg(sbi->sb, KERN_INFO,
+			"Skipping Checkpoint. Checkpoints currently disabled.");
+		return -EINVAL;
+	}
+
 	ret = mnt_want_write_file(filp);
 	if (ret)
 		return ret;
@@ -2489,6 +2504,9 @@ static int f2fs_ioc_flush_device(struct file *filp, unsigned long arg)
 	if (f2fs_readonly(sbi->sb))
 		return -EROFS;
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return -EINVAL;
+
 	if (copy_from_user(&range, (struct f2fs_flush_device __user *)arg,
 							sizeof(range)))
 		return -EFAULT;
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 9093be6e7a7db..4100dced6c309 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -60,6 +60,9 @@ static int gc_thread_func(void *data)
 		}
 #endif
 
+		if (test_opt(sbi, DISABLE_CHECKPOINT))
+			goto do_balance;
+
 		if (!sb_start_write_trylock(sbi->sb))
 			continue;
 
@@ -105,6 +108,7 @@ static int gc_thread_func(void *data)
 		trace_f2fs_background_gc(sbi->sb, wait_ms,
 				prefree_segments(sbi), free_segments(sbi));
 
+do_balance:
 		/* balancing f2fs's metadata periodically */
 		f2fs_balance_fs_bg(sbi);
 next:
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9efce174c51a9..608bf53d81f54 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -179,6 +179,10 @@ bool f2fs_need_SSR(struct f2fs_sb_info *sbi)
 		return false;
 	if (sbi->gc_mode == GC_URGENT)
 		return true;
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return true;
+	if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
+		return true;
 
 	return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
 			SM_I(sbi)->min_ssr_sections + reserved_sections(sbi));
@@ -479,7 +483,8 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
 	 * We should do GC or end up with checkpoint, if there are so many dirty
 	 * dir/node pages without enough free segments.
 	 */
-	if (has_not_enough_free_secs(sbi, 0, 0)) {
+	if (has_not_enough_free_secs(sbi, 0, 0) &&
+			!test_opt(sbi, DISABLE_CHECKPOINT)) {
 		mutex_lock(&sbi->gc_mutex);
 		f2fs_gc(sbi, false, false, NULL_SEGNO);
 	}
@@ -519,8 +524,10 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
 			f2fs_sync_dirty_inodes(sbi, FILE_INODE);
 			blk_finish_plug(&plug);
 		}
-		f2fs_sync_fs(sbi->sb, true);
-		stat_inc_bg_cp_count(sbi->stat_info);
+		if (!test_opt(sbi, DISABLE_CHECKPOINT)) {
+			f2fs_sync_fs(sbi->sb, true);
+			stat_inc_bg_cp_count(sbi->stat_info);
+		}
 	}
 }
 
@@ -735,52 +742,6 @@ int f2fs_flush_device_cache(struct f2fs_sb_info *sbi)
 	return ret;
 }
 
-static void __locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
-		enum dirty_type dirty_type)
-{
-	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-
-	/* need not be added */
-	if (IS_CURSEG(sbi, segno))
-		return;
-
-	if (!test_and_set_bit(segno, dirty_i->dirty_segmap[dirty_type]))
-		dirty_i->nr_dirty[dirty_type]++;
-
-	if (dirty_type == DIRTY) {
-		struct seg_entry *sentry = get_seg_entry(sbi, segno);
-		enum dirty_type t = sentry->type;
-
-		if (unlikely(t >= DIRTY)) {
-			f2fs_bug_on(sbi, 1);
-			return;
-		}
-		if (!test_and_set_bit(segno, dirty_i->dirty_segmap[t]))
-			dirty_i->nr_dirty[t]++;
-	}
-}
-
-static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
-		enum dirty_type dirty_type)
-{
-	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-
-	if (test_and_clear_bit(segno, dirty_i->dirty_segmap[dirty_type]))
-		dirty_i->nr_dirty[dirty_type]--;
-
-	if (dirty_type == DIRTY) {
-		struct seg_entry *sentry = get_seg_entry(sbi, segno);
-		enum dirty_type t = sentry->type;
-
-		if (test_and_clear_bit(segno, dirty_i->dirty_segmap[t]))
-			dirty_i->nr_dirty[t]--;
-
-		if (get_valid_blocks(sbi, segno, true) == 0)
-			clear_bit(GET_SEC_FROM_SEG(sbi, segno),
-						dirty_i->victim_secmap);
-	}
-}
-
 /*
  * Should not occur error such as -ENOMEM.
  * Adding dirty entry into seglist is not critical operation.
@@ -789,7 +750,7 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
 static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 {
 	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
-	unsigned short valid_blocks;
+	unsigned short valid_blocks, ckpt_valid_blocks;
 
 	if (segno == NULL_SEGNO || IS_CURSEG(sbi, segno))
 		return;
@@ -797,8 +758,10 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 	mutex_lock(&dirty_i->seglist_lock);
 
 	valid_blocks = get_valid_blocks(sbi, segno, false);
+	ckpt_valid_blocks = get_ckpt_valid_blocks(sbi, segno);
 
-	if (valid_blocks == 0) {
+	if (valid_blocks == 0 && (ckpt_valid_blocks == sbi->blocks_per_seg ||
+					!test_opt(sbi, DISABLE_CHECKPOINT))) {
 		__locate_dirty_segment(sbi, segno, PRE);
 		__remove_dirty_segment(sbi, segno, DIRTY);
 	} else if (valid_blocks < sbi->blocks_per_seg) {
@@ -1852,7 +1815,8 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
 			sbi->discard_blks--;
 
 		/* don't overwrite by SSR to keep node chain */
-		if (IS_NODESEG(se->type)) {
+		if (IS_NODESEG(se->type) &&
+				!test_opt(sbi, DISABLE_CHECKPOINT)) {
 			if (!f2fs_test_and_set_bit(offset, se->ckpt_valid_map))
 				se->ckpt_valid_blocks++;
 		}
@@ -1874,6 +1838,25 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
 			f2fs_bug_on(sbi, 1);
 			se->valid_blocks++;
 			del = 0;
+		} else {
+			/* If checkpoints are off, we must not reuse data that
+			 * was used in the previous checkpoint. If it was used
+			 * before, we must track that to know how much space we
+			 * really have
+			 */
+			if (f2fs_test_bit(offset, se->ckpt_valid_map)) {
+				spin_lock(&sbi->stat_lock);
+				sbi->unusable_block_count++;
+				spin_unlock(&sbi->stat_lock);
+			} else {
+				spin_lock(&sbi->stat_lock);
+				if (IS_DATASEG(se->type))
+					sbi->free_ssr_data_block++;
+				else
+					sbi->free_ssr_node_block++;
+				spin_unlock(&sbi->stat_lock);
+			}
+
 		}
 
 		if (f2fs_discard_en(sbi) &&
@@ -2163,7 +2146,8 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
 		return SIT_I(sbi)->last_victim[ALLOC_NEXT];
 
 	/* find segments from 0 to reuse freed segments */
-	if (F2FS_OPTION(sbi).alloc_mode == ALLOC_MODE_REUSE)
+	if (F2FS_OPTION(sbi).alloc_mode == ALLOC_MODE_REUSE
+			|| test_opt(sbi, DISABLE_CHECKPOINT))
 		return 0;
 
 	return CURSEG_I(sbi, type)->segno;
@@ -2315,7 +2299,8 @@ static void allocate_segment_by_default(struct f2fs_sb_info *sbi,
 	else if (!is_set_ckpt_flags(sbi, CP_CRC_RECOVERY_FLAG) &&
 					type == CURSEG_WARM_NODE)
 		new_curseg(sbi, type, false);
-	else if (curseg->alloc_type == LFS && is_next_segment_free(sbi, type))
+	else if (curseg->alloc_type == LFS && is_next_segment_free(sbi, type) &&
+			!test_opt(sbi, DISABLE_CHECKPOINT))
 		new_curseg(sbi, type, false);
 	else if (f2fs_need_SSR(sbi) && get_ssr_segment(sbi, type))
 		change_curseg(sbi, type);
@@ -3476,6 +3461,9 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 			sit_i->dirty_sentries--;
 			ses->entry_cnt--;
 		}
+		spin_lock(&sbi->stat_lock);
+		sbi->unusable_block_count = 0;
+		spin_unlock(&sbi->stat_lock);
 
 		if (to_journal)
 			up_write(&curseg->journal_rwsem);
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index f18fc82fbe998..9789cadc16569 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -342,6 +342,12 @@ static inline unsigned int get_valid_blocks(struct f2fs_sb_info *sbi,
 		return get_seg_entry(sbi, segno)->valid_blocks;
 }
 
+static inline unsigned int get_ckpt_valid_blocks(struct f2fs_sb_info *sbi,
+				unsigned int segno)
+{
+	return get_seg_entry(sbi, segno)->ckpt_valid_blocks;
+}
+
 static inline void seg_info_from_raw_sit(struct seg_entry *se,
 					struct f2fs_sit_entry *rs)
 {
@@ -521,6 +527,66 @@ static inline unsigned int dirty_segments(struct f2fs_sb_info *sbi)
 		DIRTY_I(sbi)->nr_dirty[DIRTY_COLD_NODE];
 }
 
+static inline void __locate_dirty_segment(struct f2fs_sb_info *sbi,
+		unsigned int segno, enum dirty_type dirty_type)
+{
+	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+
+	/* need not be added */
+	if (IS_CURSEG(sbi, segno))
+		return;
+
+	if (!test_and_set_bit(segno, dirty_i->dirty_segmap[dirty_type]))
+		dirty_i->nr_dirty[dirty_type]++;
+
+	if (dirty_type == DIRTY) {
+		struct seg_entry *sentry = get_seg_entry(sbi, segno);
+		enum dirty_type t = sentry->type;
+
+		if (unlikely(t >= DIRTY)) {
+			f2fs_bug_on(sbi, 1);
+			return;
+		}
+		if (!test_and_set_bit(segno, dirty_i->dirty_segmap[t]))
+			dirty_i->nr_dirty[t]++;
+	}
+}
+
+static inline void __remove_dirty_segment(struct f2fs_sb_info *sbi,
+		unsigned int segno, enum dirty_type dirty_type)
+{
+	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+
+	if (test_and_clear_bit(segno, dirty_i->dirty_segmap[dirty_type]))
+		dirty_i->nr_dirty[dirty_type]--;
+
+	if (dirty_type == DIRTY) {
+		struct seg_entry *sentry = get_seg_entry(sbi, segno);
+		enum dirty_type t = sentry->type;
+
+		if (test_and_clear_bit(segno, dirty_i->dirty_segmap[t]))
+			dirty_i->nr_dirty[t]--;
+
+		if (get_valid_blocks(sbi, segno, true) == 0)
+			clear_bit(GET_SEC_FROM_SEG(sbi, segno),
+						dirty_i->victim_secmap);
+	}
+}
+
+/* This moves currently empty dirty blocks to prefree. Must hold seglist_lock */
+static inline void dirty_to_prefree(struct f2fs_sb_info *sbi)
+{
+	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+	unsigned int segno;
+
+	for_each_set_bit(segno, dirty_i->dirty_segmap[DIRTY], MAIN_SEGS(sbi)) {
+		if (!get_valid_blocks(sbi, segno, false)) {
+			__locate_dirty_segment(sbi, segno, PRE);
+			__remove_dirty_segment(sbi, segno, DIRTY);
+		}
+	}
+}
+
 static inline int overprovision_segments(struct f2fs_sb_info *sbi)
 {
 	return SM_I(sbi)->ovp_segments;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1cb5d1e4fcfd2..78b46f1b9000e 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -132,6 +132,7 @@ enum {
 	Opt_alloc,
 	Opt_fsync,
 	Opt_test_dummy_encryption,
+	Opt_checkpoint,
 	Opt_err,
 };
 
@@ -189,6 +190,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_alloc, "alloc_mode=%s"},
 	{Opt_fsync, "fsync_mode=%s"},
 	{Opt_test_dummy_encryption, "test_dummy_encryption"},
+	{Opt_checkpoint, "checkpoint=%s"},
 	{Opt_err, NULL},
 };
 
@@ -764,6 +766,23 @@ static int parse_options(struct super_block *sb, char *options)
 					"Test dummy encryption mount option ignored");
 #endif
 			break;
+		case Opt_checkpoint:
+			name = match_strdup(&args[0]);
+			if (!name)
+				return -ENOMEM;
+
+			if (strlen(name) == 6 &&
+					!strncmp(name, "enable", 6)) {
+				clear_opt(sbi, DISABLE_CHECKPOINT);
+			} else if (strlen(name) == 7 &&
+					!strncmp(name, "disable", 7)) {
+				set_opt(sbi, DISABLE_CHECKPOINT);
+			} else {
+				kfree(name);
+				return -EINVAL;
+			}
+			kfree(name);
+			break;
 		default:
 			f2fs_msg(sb, KERN_ERR,
 				"Unrecognized mount option \"%s\" or missing value",
@@ -809,6 +828,11 @@ static int parse_options(struct super_block *sb, char *options)
 		}
 	}
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT) && test_opt(sbi, LFS)) {
+		f2fs_msg(sb, KERN_ERR,
+				"LFS not compatible with checkpoint=disable\n");
+	}
+
 	/* Not pass down write hints if the number of active logs is lesser
 	 * than NR_CURSEG_TYPE.
 	 */
@@ -996,8 +1020,9 @@ static void f2fs_put_super(struct super_block *sb)
 	 * But, the previous checkpoint was not done by umount, it needs to do
 	 * clean checkpoint again.
 	 */
-	if (is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
-			!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
+	if ((is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
+			!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) &&
+			!test_opt(sbi, DISABLE_CHECKPOINT)) {
 		struct cp_control cpc = {
 			.reason = CP_UMOUNT,
 		};
@@ -1007,7 +1032,8 @@ static void f2fs_put_super(struct super_block *sb)
 	/* be sure to wait for any on-going discard commands */
 	dropped = f2fs_wait_discard_bios(sbi);
 
-	if (f2fs_discard_en(sbi) && !sbi->discard_blks && !dropped) {
+	if (f2fs_discard_en(sbi) && !sbi->discard_blks && !dropped &&
+			!test_opt(sbi, DISABLE_CHECKPOINT)) {
 		struct cp_control cpc = {
 			.reason = CP_UMOUNT | CP_TRIMMED,
 		};
@@ -1064,6 +1090,8 @@ int f2fs_sync_fs(struct super_block *sb, int sync)
 
 	if (unlikely(f2fs_cp_error(sbi)))
 		return 0;
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		return 0;
 
 	trace_f2fs_sync_fs(sb, sync);
 
@@ -1162,7 +1190,8 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 	buf->f_blocks = total_count - start_count;
 	buf->f_bfree = user_block_count - valid_user_blocks(sbi) -
-						sbi->current_reserved_blocks;
+						sbi->current_reserved_blocks -
+						sbi->unusable_block_count;
 	if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks)
 		buf->f_bavail = buf->f_bfree -
 				F2FS_OPTION(sbi).root_reserved_blocks;
@@ -1338,6 +1367,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	else if (F2FS_OPTION(sbi).alloc_mode == ALLOC_MODE_REUSE)
 		seq_printf(seq, ",alloc_mode=%s", "reuse");
 
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		seq_puts(seq, ",checkpoint=disable");
+
 	if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_POSIX)
 		seq_printf(seq, ",fsync_mode=%s", "posix");
 	else if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
@@ -1362,6 +1394,7 @@ static void default_options(struct f2fs_sb_info *sbi)
 	set_opt(sbi, INLINE_DENTRY);
 	set_opt(sbi, EXTENT_CACHE);
 	set_opt(sbi, NOHEAP);
+	clear_opt(sbi, DISABLE_CHECKPOINT);
 	sbi->sb->s_flags |= SB_LAZYTIME;
 	set_opt(sbi, FLUSH_MERGE);
 	if (f2fs_sb_has_blkzoned(sbi->sb)) {
@@ -1384,6 +1417,60 @@ static void default_options(struct f2fs_sb_info *sbi)
 #ifdef CONFIG_QUOTA
 static int f2fs_enable_quotas(struct super_block *sb);
 #endif
+
+static void f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
+{
+	struct cp_control cpc;
+	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+	unsigned int segno;
+	int type;
+
+	set_sbi_flag(sbi, SBI_CP_DISABLED);
+
+	cpc.reason = CP_PAUSE;
+
+	mutex_lock(&sbi->gc_mutex);
+	write_checkpoint(sbi, &cpc);
+	mutex_unlock(&sbi->gc_mutex);
+
+	mutex_lock(&dirty_i->seglist_lock);
+	for (type = 0; type < NR_CURSEG_TYPE; type++) {
+		for_each_set_bit(segno, dirty_i->dirty_segmap[type],
+							MAIN_SEGS(sbi)) {
+			if (IS_DATASEG(type))
+				sbi->free_ssr_data_block +=
+					get_valid_blocks(sbi, segno, false);
+			else
+				sbi->free_ssr_node_block +=
+					get_valid_blocks(sbi, segno, false);
+		}
+	}
+	sbi->free_segments = FREE_I(sbi)->free_segments;
+	mutex_unlock(&dirty_i->seglist_lock);
+}
+
+static void f2fs_enable_checkpoint(struct f2fs_sb_info *sbi)
+{
+	struct super_block *sb = sbi->sb;
+	struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
+
+	clear_sbi_flag(sbi, SBI_CP_DISABLED);
+	writeback_inodes_sb(sb, WB_REASON_SYNC);
+	sync_inodes_sb(sb);
+
+	mutex_lock(&dirty_i->seglist_lock);
+	dirty_to_prefree(sbi);
+	sbi->free_segments = 0;
+	sbi->free_ssr_data_block = 0;
+	sbi->free_ssr_node_block = 0;
+	mutex_unlock(&dirty_i->seglist_lock);
+
+	set_sbi_flag(sbi, SBI_IS_DIRTY);
+	set_sbi_flag(sbi, SBI_IS_CLOSE);
+	f2fs_sync_fs(sb, 1);
+	clear_sbi_flag(sbi, SBI_IS_CLOSE);
+}
+
 static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
@@ -1393,6 +1480,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool need_restart_gc = false;
 	bool need_stop_gc = false;
 	bool no_extent_cache = !test_opt(sbi, EXTENT_CACHE);
+	bool disable_checkpoint = test_opt(sbi, DISABLE_CHECKPOINT);
+	bool checkpoint_changed;
 #ifdef CONFIG_QUOTA
 	int i, j;
 #endif
@@ -1437,6 +1526,8 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	err = parse_options(sb, data);
 	if (err)
 		goto restore_opts;
+	checkpoint_changed =
+			disable_checkpoint != test_opt(sbi, DISABLE_CHECKPOINT);
 
 	/*
 	 * Previous and new state of filesystem is RO,
@@ -1498,6 +1589,13 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		clear_sbi_flag(sbi, SBI_IS_CLOSE);
 	}
 
+	if (checkpoint_changed) {
+		if (test_opt(sbi, DISABLE_CHECKPOINT))
+			f2fs_disable_checkpoint(sbi);
+		else
+			f2fs_enable_checkpoint(sbi);
+	}
+
 	/*
 	 * We stop issue flush thread if FS is mounted as RO
 	 * or if flush_merge is not passed in mount option.
@@ -2944,7 +3042,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 		goto free_meta;
 
 	/* recover fsynced data */
-	if (!test_opt(sbi, DISABLE_ROLL_FORWARD)) {
+	if (!test_opt(sbi, DISABLE_ROLL_FORWARD) &&
+			!is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
 		/*
 		 * mount should be failed, when device has readonly mode, and
 		 * previous checkpoint was not done by clean system shutdown.
@@ -3010,6 +3109,12 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 				cur_cp_version(F2FS_CKPT(sbi)));
 	f2fs_update_time(sbi, CP_TIME);
 	f2fs_update_time(sbi, REQ_TIME);
+
+	if (test_opt(sbi, DISABLE_CHECKPOINT))
+		f2fs_disable_checkpoint(sbi);
+	else if (is_sbi_flag_set(sbi, SBI_CP_DISABLED))
+		f2fs_enable_checkpoint(sbi);
+
 	return 0;
 
 free_meta:
-- 
2.18.0.203.gfac676dfb9-goog