[PATCH 1/2] btrfs-progs: mkfs: Enhance minimal device size calculation to fix mkfs failure on small file

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

Since commit c11e36a29e84 ("Btrfs-progs: Do not force mixed block group
creation unless '-M' option is specified"), mkfs no longer use mixed
block group unless specified manually.

This breaks the minimal device size calculation, which only considered
mixed block group use case.

This patch enhances minimal device size calculation for mkfs, by using
different minimal stripe length (calculated from code) for different
profiles, and use them to calculate minimal device size.

Reported-by: Wesley Aptekar-Cassels <W.Aptekar@gmail.com>
Fixes: c11e36a29e84 ("Btrfs-progs: Do not force mixed block group creation unless '-M' option is specified")
Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
---
 mkfs/common.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++--------
 mkfs/common.h |  7 +++---
 mkfs/main.c   | 12 ++++++----
 3 files changed, 77 insertions(+), 16 deletions(-)

diff --git a/mkfs/common.c b/mkfs/common.c
index c9ce10d46a9d..64461daf3917 100644
--- a/mkfs/common.c
+++ b/mkfs/common.c
@@ -438,12 +438,6 @@ out:
 	return ret;
 }
 
-u64 btrfs_min_dev_size(u32 nodesize)
-{
-	return 2 * (BTRFS_MKFS_SYSTEM_GROUP_SIZE +
-		    btrfs_min_global_blk_rsv_size(nodesize));
-}
-
 /*
  * Btrfs minimum size calculation is complicated, it should include at least:
  * 1. system group size
@@ -454,11 +448,71 @@ u64 btrfs_min_dev_size(u32 nodesize)
  * To avoid the overkill calculation, (system group + global block rsv) * 2
  * for *EACH* device should be good enough.
  */
-u64 btrfs_min_global_blk_rsv_size(u32 nodesize)
+static u64 btrfs_min_global_blk_rsv_size(u32 nodesize)
 {
 	return (u64)nodesize << 10;
 }
 
+u64 btrfs_min_dev_size(u32 nodesize, int mixed, u64 meta_profile,
+		       u64 data_profile)
+{
+	u64 reserved = 0;
+	u64 meta_size;
+	u64 data_size;
+
+	if (mixed)
+		return 2 * (BTRFS_MKFS_SYSTEM_GROUP_SIZE +
+			    btrfs_min_global_blk_rsv_size(nodesize));
+
+	/*
+	 * minimal size calculation is complex due to several factors:
+	 * 1) Temporary chunk resue
+	 *    If specified chunk profile is SINGLE, we can resue
+	 *    temporary chunks, no need to alloc new chunks.
+	 *
+	 * 2) Different minimal chunk size for different profile
+	 *    For initial sys chunk, chunk size is fixed to 4M.
+	 *    For single profile, minimal chunk size is 8M for all.
+	 *    For other profiles, minimal chunk and stripe size
+	 *    differs from 8M to 64M.
+	 *
+	 * To calculate it a little easier, here we assume we don't
+	 * reuse any temporary chunk, and calculate the size all
+	 * by ourselves.
+	 *
+	 * Temporary chunks sizes are always fixed:
+	 * One initial sys chunk, one SINGLE meta, and one SINGLE data.
+	 * The latter two are all 8M, accroding to @calc_size of
+	 * btrfs_alloc_chunk().
+	 */
+	reserved += BTRFS_MKFS_SYSTEM_GROUP_SIZE + SZ_8M * 2;
+
+	/*
+	 * For real chunks, we need to refer different sizes:
+	 * For SINGLE, it's still fixed to 8M (@calc_size).
+	 * For other profiles, refer to max(@min_stripe_size, @calc_size).
+	 *
+	 * And use the stripe size to calculate its physical used space.
+	 */
+	if (meta_profile & BTRFS_BLOCK_GROUP_PROFILE_MASK)
+		meta_size = SZ_8M + SZ_32M;
+	else
+		meta_size = SZ_8M + SZ_8M;
+	/* Only metadata put 2 stripes into one disk */
+	if (meta_profile & BTRFS_BLOCK_GROUP_DUP)
+		meta_size *= 2;
+	reserved += meta_size;
+
+	if (data_profile & BTRFS_BLOCK_GROUP_PROFILE_MASK)
+		data_size = SZ_64M;
+	else
+		data_size = SZ_8M;
+	if (data_profile & BTRFS_BLOCK_GROUP_DUP)
+		data_size *= 2;
+	reserved += data_size;
+	return reserved;
+}
+
 #define isoctal(c)	(((c) & ~7) == '0')
 
 static inline void translate(char *f, char *t)
@@ -698,7 +752,8 @@ int is_vol_small(const char *file)
 	}
 }
 
-int test_minimum_size(const char *file, u32 nodesize)
+int test_minimum_size(const char *file, u32 nodesize, int mixed,
+		      u64 meta_profile, u64 data_profile)
 {
 	int fd;
 	struct stat statbuf;
@@ -710,7 +765,8 @@ int test_minimum_size(const char *file, u32 nodesize)
 		close(fd);
 		return -errno;
 	}
-	if (btrfs_device_size(fd, &statbuf) < btrfs_min_dev_size(nodesize)) {
+	if (btrfs_device_size(fd, &statbuf) <
+	    btrfs_min_dev_size(nodesize, mixed, meta_profile, data_profile)) {
 		close(fd);
 		return 1;
 	}
diff --git a/mkfs/common.h b/mkfs/common.h
index dee0ea9740e0..0d1aa5c17c03 100644
--- a/mkfs/common.h
+++ b/mkfs/common.h
@@ -66,9 +66,10 @@ struct btrfs_mkfs_config {
 };
 
 int make_btrfs(int fd, struct btrfs_mkfs_config *cfg);
-u64 btrfs_min_dev_size(u32 nodesize);
-u64 btrfs_min_global_blk_rsv_size(u32 nodesize);
-int test_minimum_size(const char *file, u32 nodesize);
+u64 btrfs_min_dev_size(u32 nodesize, int mixed, u64 meta_profile,
+		       u64 data_profile);
+int test_minimum_size(const char *file, u32 nodesize, int mixed,
+		      u64 meta_profile, u64 data_profile);
 int is_vol_small(const char *file);
 int test_num_disk_vs_raid(u64 metadata_profile, u64 data_profile,
 	u64 dev_cnt, int mixed, int ssd);
diff --git a/mkfs/main.c b/mkfs/main.c
index 1b4cabc1ef90..527c508f64a5 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -1436,6 +1436,7 @@ int main(int argc, char **argv)
 	u64 num_of_meta_chunks = 0;
 	u64 size_of_data = 0;
 	u64 source_dir_size = 0;
+	u64 min_dev_size;
 	int dev_cnt = 0;
 	int saved_optind;
 	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE] = { 0 };
@@ -1646,19 +1647,22 @@ int main(int argc, char **argv)
 		goto error;
 	}
 
+	min_dev_size = btrfs_min_dev_size(nodesize, mixed, metadata_profile,
+					  data_profile);
 	/* Check device/block_count after the nodesize is determined */
-	if (block_count && block_count < btrfs_min_dev_size(nodesize)) {
+	if (block_count && block_count < min_dev_size) {
 		error("size %llu is too small to make a usable filesystem",
 			block_count);
 		error("minimum size for btrfs filesystem is %llu",
-			btrfs_min_dev_size(nodesize));
+			min_dev_size);
 		goto error;
 	}
 	for (i = saved_optind; i < saved_optind + dev_cnt; i++) {
 		char *path;
 
 		path = argv[i];
-		ret = test_minimum_size(path, nodesize);
+		ret = test_minimum_size(path, nodesize, mixed, metadata_profile,
+					data_profile);
 		if (ret < 0) {
 			error("failed to check size for %s: %s",
 				path, strerror(-ret));
@@ -1668,7 +1672,7 @@ int main(int argc, char **argv)
 			error("'%s' is too small to make a usable filesystem",
 				path);
 			error("minimum size for each btrfs device is %llu",
-				btrfs_min_dev_size(nodesize));
+				min_dev_size);
 			goto error;
 		}
 	}
-- 
2.14.2