f2fs: Reduce zoned block device memory usage

For zoned block devices, an array of zone types for each device is
allocated and initialized in order to determine if a section is stored
on a sequential zone (zone reset needed) or a conventional zone (no
zone reset needed and regular discard applies). Considering this usage,
the zone types stored in memory can be replaced with a bitmap to
indicate an equivalent information, that is, if a zone is sequential or
not. This reduces the memory usage for each zoned device by roughly 8:
on a 14TB disk with zones of 256 MB, the zone type array consumes
13x4KB pages while the bitmap uses only 2x4KB pages.

This patch changes the f2fs_dev_info structure blkz_type field to the
bitmap blkz_seq. Access to this bitmap is done using the helper
function f2fs_blkz_is_seq(), which is a rewrite of the function
get_blkz_type().
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1069,7 +1069,7 @@ struct f2fs_dev_info {
 	block_t end_blk;
 #ifdef CONFIG_BLK_DEV_ZONED
 	unsigned int nr_blkz;		/* Total number of zones */
-	u8 *blkz_type;				/* Array of zones type */
+	unsigned long *blkz_seq;	/* Bitmap indicating sequential zones */
 #endif
 };
 
@@ -3542,16 +3542,12 @@ F2FS_FEATURE_FUNCS(lost_found, LOST_FOUND);
 F2FS_FEATURE_FUNCS(sb_chksum, SB_CHKSUM);
 
 #ifdef CONFIG_BLK_DEV_ZONED
-static inline int get_blkz_type(struct f2fs_sb_info *sbi,
-			struct block_device *bdev, block_t blkaddr)
+static inline bool f2fs_blkz_is_seq(struct f2fs_sb_info *sbi, int devi,
+				    block_t blkaddr)
 {
 	unsigned int zno = blkaddr >> sbi->log_blocks_per_blkz;
-	int i;
 
-	for (i = 0; i < sbi->s_ndevs; i++)
-		if (FDEV(i).bdev == bdev)
-			return FDEV(i).blkz_type[zno];
-	return -EINVAL;
+	return test_bit(zno, FDEV(devi).blkz_seq);
 }
 #endif
 

fs/f2fs/segment.c

@@ -1735,40 +1735,36 @@ static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
 
 	if (f2fs_is_multi_device(sbi)) {
 		devi = f2fs_target_device_index(sbi, blkstart);
+		if (blkstart < FDEV(devi).start_blk ||
+		    blkstart > FDEV(devi).end_blk) {
+			f2fs_msg(sbi->sb, KERN_ERR, "Invalid block %x",
+				 blkstart);
+			return -EIO;
+		}
 		blkstart -= FDEV(devi).start_blk;
 	}
 
-	/*
-	 * We need to know the type of the zone: for conventional zones,
-	 * use regular discard if the drive supports it. For sequential
-	 * zones, reset the zone write pointer.
-	 */
-	switch (get_blkz_type(sbi, bdev, blkstart)) {
-
-	case BLK_ZONE_TYPE_CONVENTIONAL:
-		if (!blk_queue_discard(bdev_get_queue(bdev)))
-			return 0;
-		return __queue_discard_cmd(sbi, bdev, lblkstart, blklen);
-	case BLK_ZONE_TYPE_SEQWRITE_REQ:
-	case BLK_ZONE_TYPE_SEQWRITE_PREF:
+	/* For sequential zones, reset the zone write pointer */
+	if (f2fs_blkz_is_seq(sbi, devi, blkstart)) {
 		sector = SECTOR_FROM_BLOCK(blkstart);
 		nr_sects = SECTOR_FROM_BLOCK(blklen);
 
 		if (sector & (bdev_zone_sectors(bdev) - 1) ||
 				nr_sects != bdev_zone_sectors(bdev)) {
-			f2fs_msg(sbi->sb, KERN_INFO,
-				"(%d) %s: Unaligned discard attempted (block %x + %x)",
+			f2fs_msg(sbi->sb, KERN_ERR,
+				"(%d) %s: Unaligned zone reset attempted (block %x + %x)",
 				devi, sbi->s_ndevs ? FDEV(devi).path: "",
 				blkstart, blklen);
 			return -EIO;
 		}
 		trace_f2fs_issue_reset_zone(bdev, blkstart);
-		return blkdev_reset_zones(bdev, sector,
-					  nr_sects, GFP_NOFS);
-	default:
-		/* Unknown zone type: broken device ? */
-		return -EIO;
+		return blkdev_reset_zones(bdev, sector, nr_sects, GFP_NOFS);
 	}
+
+	/* For conventional zones, use regular discard if supported */
+	if (!blk_queue_discard(bdev_get_queue(bdev)))
+		return 0;
+	return __queue_discard_cmd(sbi, bdev, lblkstart, blklen);
 }
 #endif
 

fs/f2fs/super.c

@@ -1024,7 +1024,7 @@ static void destroy_device_list(struct f2fs_sb_info *sbi)
 	for (i = 0; i < sbi->s_ndevs; i++) {
 		blkdev_put(FDEV(i).bdev, FMODE_EXCL);
 #ifdef CONFIG_BLK_DEV_ZONED
-		kvfree(FDEV(i).blkz_type);
+		kvfree(FDEV(i).blkz_seq);
 #endif
 	}
 	kvfree(sbi->devs);
@@ -2798,9 +2798,11 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
 	if (nr_sectors & (bdev_zone_sectors(bdev) - 1))
 		FDEV(devi).nr_blkz++;
 
-	FDEV(devi).blkz_type = f2fs_kmalloc(sbi, FDEV(devi).nr_blkz,
+	FDEV(devi).blkz_seq = f2fs_kzalloc(sbi,
+					BITS_TO_LONGS(FDEV(devi).nr_blkz)
+					* sizeof(unsigned long),
 					GFP_KERNEL);
-	if (!FDEV(devi).blkz_type)
+	if (!FDEV(devi).blkz_seq)
 		return -ENOMEM;
 
 #define F2FS_REPORT_NR_ZONES   4096
@@ -2827,7 +2829,8 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
 		}
 
 		for (i = 0; i < nr_zones; i++) {
-			FDEV(devi).blkz_type[n] = zones[i].type;
+			if (zones[i].type != BLK_ZONE_TYPE_CONVENTIONAL)
+				set_bit(n, FDEV(devi).blkz_seq);
 			sector += zones[i].len;
 			n++;
 		}