[PATCH v6 3/6] btrfs: add per-inode compression levels in xattrs

[koraynilay <koray.fra@gmail.com>]

Add support for specifying algo:level using
btrfs property set /path/to/file compression "algo:level".

Add a signed 8 bit prop_compress_level property to btrfs_inode, which
can support from level -128 to 127, plenty for the currently supported
algo:level(s).

Change prop_compression_apply() to use the already present
btrfs_match_compress_type() and btrfs_compress_str2level() to parse the
xattr, using a stack-based buffer and memcpy() to convert the
user-supplied xattr value to a NUL-terminated string to be used by
btrfs_compress_str2level().

Assisted-by: Gemini:3.1-pro antigravity-cli-1.1.5
Signed-off-by: koraynilay <koray.fra@gmail.com>
---
 fs/btrfs/btrfs_inode.h |  1 +
 fs/btrfs/inode.c       | 10 ++++++++++
 fs/btrfs/props.c       | 31 ++++++++++++++++++++++++++++---
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 46c62f980c24..280b45e7ddf2 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -131,6 +131,7 @@ struct btrfs_inode {
 
 	/* Cached value of inode property 'compression'. */
 	u8 prop_compress;
+	s8 prop_compress_level;
 
 	/*
 	 * Force compression on the file using the defrag ioctl, could be
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a85a7c561cf8..2df3eb19ee30 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -942,6 +942,11 @@ static void compress_file_range(struct btrfs_work *work)
 		compress_level = inode->defrag_compress_level;
 	} else if (inode->prop_compress) {
 		compress_type = inode->prop_compress;
+		if (inode->prop_compress_level)
+			compress_level = inode->prop_compress_level;
+		else if (compress_type != fs_info->compress_type)
+			compress_level = 0;
+		/* else use fs_info->compress_level */
 	}
 
 	/* Compression level is applied here. */
@@ -2338,6 +2343,11 @@ static int run_delalloc_inline(struct btrfs_inode *inode, struct folio *locked_f
 			compress_level = inode->defrag_compress_level;
 		} else if (inode->prop_compress) {
 			compress_type = inode->prop_compress;
+			if (inode->prop_compress_level)
+				compress_level = inode->prop_compress_level;
+			else if (compress_type != fs_info->compress_type)
+				compress_level = 0;
+			/* else use fs_info->compress_level */
 		}
 		cb = btrfs_compress_bio(inode, 0, blocksize, compress_type, compress_level, 0);
 		if (IS_ERR(cb)) {
diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 2e706093e186..7b966b9e4c8d 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -332,6 +332,10 @@ static int prop_compression_apply(struct btrfs_inode *inode, const char *value,
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	int type;
+	int level = 0;
+	int ret = 0;
+	char value_str[BTRFS_COMPRESS_PROP_MAX_LEN];
+	int level_pos = 0;
 
 	/* Reset to defaults */
 	if (len == 0) {
@@ -351,21 +355,42 @@ static int prop_compression_apply(struct btrfs_inode *inode, const char *value,
 		return 0;
 	}
 
-	if (!strncmp("lzo", value, 3)) {
+	if (len >= BTRFS_COMPRESS_PROP_MAX_LEN)
+		return -EINVAL;
+
+	memcpy(value_str, value, len);
+	value_str[len] = '\0';
+
+	if (btrfs_match_compress_type(value_str, "lzo", true)) {
 		type = BTRFS_COMPRESS_LZO;
 		btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
-	} else if (!strncmp("zlib", value, 4)) {
+	} else if (btrfs_match_compress_type(value_str, "zlib", true)) {
 		type = BTRFS_COMPRESS_ZLIB;
-	} else if (!strncmp("zstd", value, 4)) {
+		level_pos = 4;
+	} else if (btrfs_match_compress_type(value_str, "zstd", true)) {
 		type = BTRFS_COMPRESS_ZSTD;
+		level_pos = 4;
 		btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
 	} else {
 		return -EINVAL;
 	}
 
+	/* Parse level if the algorithm supports it */
+	if (level_pos > 0) {
+		const char *level_str = value_str + level_pos;
+
+		/* and if user specified it */
+		if (level_str[0] == ':') {
+			ret = btrfs_compress_str2level(type, level_str, &level);
+			if (ret < 0)
+				return ret;
+		}
+	}
+
 	inode->flags &= ~BTRFS_INODE_NOCOMPRESS;
 	inode->flags |= BTRFS_INODE_COMPRESS;
 	inode->prop_compress = type;
+	inode->prop_compress_level = level;
 
 	return 0;
 }
-- 
2.55.0