btrfs: defrag: add flag to force no-compression

Currently the defrag ioctl cannot rewrite the extents without
compression. Add a new flag for that, as setting compression to 0 (or
"no compression") means to do no changes to compression so take what is
the current default, like mount options or properties.

The defrag setting overrides mount or properties. The compression
BTRFS_DEFRAG_DONT_COMPRESS is only used for in-memory operations and
does not need to have a fixed value.

Mount with zstd:9, copy test file from /usr/bin/ (about 260KB):

  $ mount -o compress=zstd:9 /dev/vda /mnt
  $ filefrag -vsb testfile
  filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
  Filesystem type is: 9123683e
  File size of testfile is 297704 (292 blocks of 1024 bytes)
   ext:     logical_offset:        physical_offset: length:   expected: flags:
     0:        0..     127:      13312..     13439:    128:             encoded
     1:      128..     255:      13364..     13491:    128:      13440: encoded
     2:      256..     291:      13424..     13459:     36:      13492: last,encoded,eof
  testfile: 3 extents found

  $ compsize testfile
  Processed 1 file, 3 regular extents (3 refs), 0 inline, 1 fragments.
  Type       Perc     Disk Usage   Uncompressed Referenced
  TOTAL       42%      124K         292K         292K
  zstd        42%      124K         292K         292K

Defrag to uncompressed:

  $ btrfs fi defrag --nocomp testfile
  $ filefrag -vsb testfile
  filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
  Filesystem type is: 9123683e
  File size of testfile is 297704 (292 blocks of 1024 bytes)
   ext:     logical_offset:        physical_offset: length:   expected: flags:
     0:        0..     291:     291840..    292131:    292:             last,eof
  testfile: 1 extent found

  $ compsize testfile
  Processed 1 file, 1 regular extents (1 refs), 0 inline, 1 fragments.
  Type       Perc     Disk Usage   Uncompressed Referenced
  TOTAL      100%      292K         292K         292K
  none       100%      292K         292K         292K

Compress again with LZO:

  $ btrfs fi defrag -clzo testfile
  $ filefrag -vsb testfile
  filefrag: -b needs a blocksize option, assuming 1024-byte blocks.
  Filesystem type is: 9123683e
  File size of testfile is 297704 (292 blocks of 1024 bytes)
   ext:     logical_offset:        physical_offset: length:   expected: flags:
     0:        0..     127:      13312..     13439:    128:             encoded
     1:      128..     255:      13392..     13519:    128:      13440: encoded
     2:      256..     291:      13480..     13515:     36:      13520: last,encoded,eof
  testfile: 3 extents found

  $ compsize testfile
  Processed 1 file, 3 regular extents (3 refs), 0 inline, 1 fragments.
  Type       Perc     Disk Usage   Uncompressed Referenced
  TOTAL       64%      188K         292K         292K
  lzo         64%      188K         292K         292K

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

fs/btrfs/compression.h

@@ -113,6 +113,8 @@ enum btrfs_compression_type {
 	BTRFS_COMPRESS_LZO   = 2,
 	BTRFS_COMPRESS_ZSTD  = 3,
 	BTRFS_NR_COMPRESS_TYPES = 4,
+
+	BTRFS_DEFRAG_DONT_COMPRESS,
 };
 
 struct workspace_manager {

fs/btrfs/defrag.c

@@ -947,7 +947,7 @@ struct defrag_target_range {
  * @extent_thresh: file extent size threshold, any extent size >= this value
  *		   will be ignored
  * @newer_than:    only defrag extents newer than this value
- * @do_compress:   whether the defrag is doing compression
+ * @do_compress:   whether the defrag is doing compression or no-compression
  *		   if true, @extent_thresh will be ignored and all regular
  *		   file extents meeting @newer_than will be targets.
  * @locked:	   if the range has already held extent lock
@@ -1364,6 +1364,7 @@ int btrfs_defrag_file(struct btrfs_inode *inode, struct file_ra_state *ra,
 	u64 cur;
 	u64 last_byte;
 	bool do_compress = (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS);
+	bool no_compress = (range->flags & BTRFS_DEFRAG_RANGE_NOCOMPRESS);
 	int compress_type = BTRFS_COMPRESS_ZLIB;
 	int compress_level = 0;
 	int ret = 0;
@@ -1394,6 +1395,9 @@ int btrfs_defrag_file(struct btrfs_inode *inode, struct file_ra_state *ra,
 			if (range->compress_type)
 				compress_type = range->compress_type;
 		}
+	} else if (range->flags & BTRFS_DEFRAG_RANGE_NOCOMPRESS) {
+		compress_type = BTRFS_DEFRAG_DONT_COMPRESS;
+		compress_level = 1;
 	}
 
 	if (extent_thresh == 0)
@@ -1444,13 +1448,14 @@ int btrfs_defrag_file(struct btrfs_inode *inode, struct file_ra_state *ra,
 			btrfs_inode_unlock(inode, 0);
 			break;
 		}
-		if (do_compress) {
+		if (do_compress || no_compress) {
 			inode->defrag_compress = compress_type;
 			inode->defrag_compress_level = compress_level;
 		}
 		ret = defrag_one_cluster(inode, ra, cur,
 				cluster_end + 1 - cur, extent_thresh,
-				newer_than, do_compress, &sectors_defragged,
+				newer_than, do_compress || no_compress,
+				&sectors_defragged,
 				max_to_defrag, &last_scanned);
 
 		if (sectors_defragged > prev_sectors_defragged)
@@ -1489,7 +1494,7 @@ int btrfs_defrag_file(struct btrfs_inode *inode, struct file_ra_state *ra,
 			btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
 		ret = sectors_defragged;
 	}
-	if (do_compress) {
+	if (do_compress || no_compress) {
 		btrfs_inode_lock(inode, 0);
 		inode->defrag_compress = BTRFS_COMPRESS_NONE;
 		btrfs_inode_unlock(inode, 0);

fs/btrfs/inode.c

@@ -781,12 +781,15 @@ static inline int inode_need_compress(struct btrfs_inode *inode, u64 start,
 		return 0;
 	}
 
+	/* Defrag ioctl takes precedence over mount options and properties. */
+	if (inode->defrag_compress == BTRFS_DEFRAG_DONT_COMPRESS)
+		return 0;
+	if (BTRFS_COMPRESS_NONE < inode->defrag_compress &&
+	    inode->defrag_compress < BTRFS_NR_COMPRESS_TYPES)
+		return 1;
 	/* force compress */
 	if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
 		return 1;
-	/* defrag ioctl */
-	if (inode->defrag_compress)
-		return 1;
 	/* bad compression ratios */
 	if (inode->flags & BTRFS_INODE_NOCOMPRESS)
 		return 0;
@@ -942,7 +945,7 @@ static void compress_file_range(struct btrfs_work *work)
 		goto cleanup_and_bail_uncompressed;
 	}
 
-	if (inode->defrag_compress) {
+	if (0 < inode->defrag_compress && inode->defrag_compress < BTRFS_NR_COMPRESS_TYPES) {
 		compress_type = inode->defrag_compress;
 		compress_level = inode->defrag_compress_level;
 	} else if (inode->prop_compress) {

fs/btrfs/ioctl.c

@@ -2554,8 +2554,14 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 				ret = -EOPNOTSUPP;
 				goto out;
 			}
-			/* compression requires us to start the IO */
-			if ((range.flags & BTRFS_DEFRAG_RANGE_COMPRESS)) {
+			if ((range.flags & BTRFS_DEFRAG_RANGE_COMPRESS) &&
+			    (range.flags & BTRFS_DEFRAG_RANGE_NOCOMPRESS)) {
+				ret = -EINVAL;
+				goto out;
+			}
+			/* Compression or no-compression require to start the IO. */
+			if ((range.flags & BTRFS_DEFRAG_RANGE_COMPRESS) ||
+			    (range.flags & BTRFS_DEFRAG_RANGE_NOCOMPRESS)) {
 				range.flags |= BTRFS_DEFRAG_RANGE_START_IO;
 				range.extent_thresh = (u32)-1;
 			}

include/uapi/linux/btrfs.h

@@ -616,8 +616,11 @@ struct btrfs_ioctl_clone_range_args {
 #define BTRFS_DEFRAG_RANGE_COMPRESS 1
 #define BTRFS_DEFRAG_RANGE_START_IO 2
 #define BTRFS_DEFRAG_RANGE_COMPRESS_LEVEL 4
+/* Request no compression on the range (uncompress if necessary). */
+#define BTRFS_DEFRAG_RANGE_NOCOMPRESS	8
 #define BTRFS_DEFRAG_RANGE_FLAGS_SUPP	(BTRFS_DEFRAG_RANGE_COMPRESS |		\
 					 BTRFS_DEFRAG_RANGE_COMPRESS_LEVEL |	\
+					 BTRFS_DEFRAG_RANGE_NOCOMPRESS |	\
 					 BTRFS_DEFRAG_RANGE_START_IO)
 
 struct btrfs_ioctl_defrag_range_args {