Message-ID: <20260206182336.1397715-27-neelx@suse.com>
Date: Fri,  6 Feb 2026 19:22:58 +0100
From: Daniel Vacek <neelx@...e.com>
To: Chris Mason <clm@...com>,
	Josef Bacik <josef@...icpanda.com>,
	Eric Biggers <ebiggers@...nel.org>,
	"Theodore Y. Ts'o" <tytso@....edu>,
	Jaegeuk Kim <jaegeuk@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	David Sterba <dsterba@...e.com>
Cc: linux-block@...r.kernel.org,
	Daniel Vacek <neelx@...e.com>,
	linux-fscrypt@...r.kernel.org,
	linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v6 26/43] btrfs: implement the fscrypt extent encryption hooks

From: Josef Bacik <josef@...icpanda.com>

This patch implements the necessary hooks from fscrypt to support
per-extent encryption.  There's two main entry points

btrfs_fscrypt_load_extent_info
btrfs_fscrypt_save_extent_info

btrfs_fscrypt_load_extent_info gets called when we create the extent
maps from the file extent item at btrfs_get_extent() time.  We read the
extent context, and pass it into fscrypt to create the appropriate
fscrypt_extent_info structure.  This is then used on the bio's to make
sure the encryption is done properly.

btrfs_fscrypt_save_extent_info is used to generate the fscrypt context
from fscrypt and save it into the tree item when we create a new
file extent item.

Signed-off-by: Josef Bacik <josef@...icpanda.com>
Signed-off-by: Daniel Vacek <neelx@...e.com>
---

v5: https://lore.kernel.org/linux-btrfs/30eaad31964c88c3497a0c5bc8f2c727c1dc763a.1706116485.git.josef@toxicpanda.com/
 * Also significantly reworked due to the changes in previous commit [24/43].
---
 fs/btrfs/ctree.h    |  3 ++
 fs/btrfs/defrag.c   |  6 ++++
 fs/btrfs/file.c     | 11 ++++++
 fs/btrfs/fscrypt.c  | 84 +++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/fscrypt.h  | 29 ++++++++++++++++
 fs/btrfs/inode.c    | 36 +++++++++++++++++++
 fs/btrfs/reflink.c  | 43 ++++++++++++++++++++++-
 fs/btrfs/tree-log.c | 19 ++++++++++
 8 files changed, 230 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 6de7ad191e04..89d3c3137786 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -400,6 +400,9 @@ struct btrfs_replace_extent_info {
 	u64 file_offset;
 	/* Pointer to a file extent item of type regular or prealloc. */
 	char *extent_buf;
+	/* The fscrypt_extent_info for a new extent. */
+	u8 *fscrypt_ctx;
+	u32 fscrypt_context_size;
 	/*
 	 * Set to true when attempting to replace a file range with a new extent
 	 * described by this structure, set to false when attempting to clone an
diff --git a/fs/btrfs/defrag.c b/fs/btrfs/defrag.c
index ecf05cd64696..f64c0502cef9 100644
--- a/fs/btrfs/defrag.c
+++ b/fs/btrfs/defrag.c
@@ -16,6 +16,7 @@
 #include "file-item.h"
 #include "super.h"
 #include "compression.h"
+#include "fscrypt.h"
 
 static struct kmem_cache *btrfs_inode_defrag_cachep;
 
@@ -720,6 +721,11 @@ static struct extent_map *defrag_get_extent(struct btrfs_inode *inode,
 		if (ret > 0)
 			goto not_found;
 	}
+	btrfs_release_path(&path);
+
+	ret = btrfs_fscrypt_load_extent_info(inode, &path, &key, em);
+	if (ret)
+		goto err;
 	return em;
 
 not_found:
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 639462164d08..89cd4f49e84b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -37,6 +37,7 @@
 #include "file.h"
 #include "super.h"
 #include "print-tree.h"
+#include "fscrypt.h"
 
 /*
  * Unlock folio after btrfs_file_write() is done with it.
@@ -2401,6 +2402,16 @@ static int btrfs_insert_replace_extent(struct btrfs_trans_handle *trans,
 	if (extent_info->is_new_extent)
 		btrfs_set_file_extent_generation(leaf, extent, trans->transid);
 	btrfs_release_path(path);
+	if (extent_info->fscrypt_context_size) {
+		key.type = BTRFS_FSCRYPT_CTX_KEY;
+		ret = btrfs_insert_empty_item(trans, root, path, &key,
+					      extent_info->fscrypt_context_size);
+		if (ret)
+			return ret;
+		btrfs_fscrypt_save_extent_info(path,
+					       extent_info->fscrypt_ctx,
+					       extent_info->fscrypt_context_size);
+	}
 
 	ret = btrfs_inode_set_file_extent_range(inode, extent_info->file_offset,
 						replace_len);
diff --git a/fs/btrfs/fscrypt.c b/fs/btrfs/fscrypt.c
index 608f8797ea6f..26060f3e50de 100644
--- a/fs/btrfs/fscrypt.c
+++ b/fs/btrfs/fscrypt.c
@@ -212,9 +212,93 @@ static struct block_device **btrfs_fscrypt_get_devices(struct super_block *sb,
 	return devs;
 }
 
+int btrfs_fscrypt_load_extent_info(struct btrfs_inode *inode,
+				   struct btrfs_path *path,
+				   struct btrfs_key *key,
+				   struct extent_map *em)
+{
+	struct extent_buffer *leaf;
+	int slot;
+	unsigned long offset;
+	u8 ctx[BTRFS_MAX_EXTENT_CTX_SIZE];
+	unsigned long size;
+	struct fscrypt_extent_info *info;
+	unsigned long nofs_flag;
+	int ret;
+
+	if (em->disk_bytenr == EXTENT_MAP_HOLE)
+		return 0;
+	if (btrfs_extent_map_encryption(em) != BTRFS_ENCRYPTION_FSCRYPT)
+		return 0;
+
+	key->type = BTRFS_FSCRYPT_CTX_KEY;
+	ret = btrfs_search_slot(NULL, inode->root, key, path, 0, 0);
+	leaf = path->nodes[0];
+	slot = path->slots[0];
+	if (ret) {
+		btrfs_err(leaf->fs_info,
+	"missing or error searching encryption context item in leaf: root=%llu block=%llu slot=%d ino=%llu file_offset=%llu, err %i",
+			  btrfs_header_owner(leaf), btrfs_header_bytenr(leaf), slot,
+			  key->objectid, key->offset, ret);
+		btrfs_release_path(path);
+		return ret;
+	}
+
+	size = btrfs_item_size(leaf, slot);
+	if (size > FSCRYPT_SET_CONTEXT_MAX_SIZE) {
+		btrfs_err(leaf->fs_info,
+	"unexpected or corrupted encryption context size in leaf: root=%llu block=%llu slot=%d ino=%llu file_offset=%llu, size %lu (too big)",
+			  btrfs_header_owner(leaf), btrfs_header_bytenr(leaf), slot,
+			  key->objectid, key->offset, size);
+		btrfs_release_path(path);
+		return -EIO;
+	}
+
+	offset = btrfs_item_ptr_offset(leaf, slot),
+	read_extent_buffer(leaf, ctx, offset, size);
+	btrfs_release_path(path);
+
+	nofs_flag = memalloc_nofs_save();
+	info = fscrypt_load_extent_info(&inode->vfs_inode, ctx, size);
+	memalloc_nofs_restore(nofs_flag);
+	if (IS_ERR(info))
+		return PTR_ERR(info);
+	em->fscrypt_info = info;
+	return 0;
+}
+
+void btrfs_fscrypt_save_extent_info(struct btrfs_path *path, u8 *ctx, unsigned long size)
+{
+	struct extent_buffer *leaf = path->nodes[0];
+	unsigned long offset = btrfs_item_ptr_offset(leaf, path->slots[0]);
+
+	ASSERT(size <= FSCRYPT_SET_CONTEXT_MAX_SIZE);
+
+	write_extent_buffer(leaf, ctx, offset, size);
+	btrfs_release_path(path);
+}
+
+ssize_t btrfs_fscrypt_context_for_new_extent(struct btrfs_inode *inode,
+					     struct fscrypt_extent_info *info,
+					     u8 *ctx)
+{
+	ssize_t ret;
+
+	if (!info)
+		return 0;
+
+	ret = fscrypt_context_for_new_extent(&inode->vfs_inode, info, ctx);
+	if (ret < 0) {
+		btrfs_err_rl(inode->root->fs_info, "invalid encrypt context");
+		return ret;
+	}
+	return ret;
+}
+
 const struct fscrypt_operations btrfs_fscrypt_ops = {
 	.inode_info_offs = (int)offsetof(struct btrfs_inode, i_crypt_info) -
 			   (int)offsetof(struct btrfs_inode, vfs_inode),
+	.has_per_extent_encryption = 1,
 	.get_context = btrfs_fscrypt_get_context,
 	.set_context = btrfs_fscrypt_set_context,
 	.empty_dir = btrfs_fscrypt_empty_dir,
diff --git a/fs/btrfs/fscrypt.h b/fs/btrfs/fscrypt.h
index c5cdc27f943c..68eab4606935 100644
--- a/fs/btrfs/fscrypt.h
+++ b/fs/btrfs/fscrypt.h
@@ -16,8 +16,27 @@ int btrfs_fscrypt_get_disk_name(struct extent_buffer *leaf,
 bool btrfs_fscrypt_match_name(struct fscrypt_name *fname,
 			      struct extent_buffer *leaf,
 			      unsigned long de_name, u32 de_name_len);
+int btrfs_fscrypt_load_extent_info(struct btrfs_inode *inode,
+				   struct btrfs_path *path,
+				   struct btrfs_key *key,
+				   struct extent_map *em);
+void btrfs_fscrypt_save_extent_info(struct btrfs_path *path, u8 *ctx, unsigned long size);
+ssize_t btrfs_fscrypt_context_for_new_extent(struct btrfs_inode *inode,
+					     struct fscrypt_extent_info *info,
+					     u8 *ctx);
 
 #else
+static inline void btrfs_fscrypt_save_extent_info(struct btrfs_path *path,
+						  u8 *ctx, unsigned long size) { }
+
+static inline int btrfs_fscrypt_load_extent_info(struct btrfs_inode *inode,
+						 struct btrfs_path *path,
+						 struct btrfs_key *key,
+						 struct extent_map *em)
+{
+	return 0;
+}
+
 static inline int btrfs_fscrypt_get_disk_name(struct extent_buffer *leaf,
 					      struct btrfs_dir_item *di,
 					      struct fscrypt_str *qstr)
@@ -34,6 +53,16 @@ static inline bool btrfs_fscrypt_match_name(struct fscrypt_name *fname,
 		return false;
 	return !memcmp_extent_buffer(leaf, fname->disk_name.name, de_name, de_name_len);
 }
+
+static inline ssize_t btrfs_fscrypt_context_for_new_extent(struct btrfs_inode *inode,
+							   struct fscrypt_extent_info *info,
+							   u8 *ctx)
+{
+	if (!info)
+		return 0;
+	return -EINVAL;
+}
+
 #endif /* CONFIG_FS_ENCRYPTION */
 
 extern const struct fscrypt_operations btrfs_fscrypt_ops;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f449839d6d84..15191dffa354 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3036,8 +3036,16 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	u64 num_bytes = btrfs_stack_file_extent_num_bytes(stack_fi);
 	u64 ram_bytes = btrfs_stack_file_extent_ram_bytes(stack_fi);
 	struct btrfs_drop_extents_args drop_args = { 0 };
+	u8 fscrypt_ctx[FSCRYPT_SET_CONTEXT_MAX_SIZE];
+	ssize_t fscrypt_context_size;
 	int ret;
 
+	fscrypt_context_size = btrfs_fscrypt_context_for_new_extent(inode,
+								    fscrypt_info,
+								    fscrypt_ctx);
+	if (fscrypt_context_size < 0)
+		return (int)fscrypt_context_size;
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
@@ -3078,6 +3086,16 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 
 	btrfs_release_path(path);
 
+	if (fscrypt_context_size) {
+		ins.objectid = btrfs_ino(inode);
+		ins.type = BTRFS_FSCRYPT_CTX_KEY;
+		ins.offset = file_pos;
+		ret = btrfs_insert_empty_item(trans, root, path, &ins, fscrypt_context_size);
+		if (ret)
+			return ret;
+		btrfs_fscrypt_save_extent_info(path, fscrypt_ctx, fscrypt_context_size);
+	}
+
 	/*
 	 * If we dropped an inline extent here, we know the range where it is
 	 * was not marked with the EXTENT_DELALLOC_NEW bit, so we update the
@@ -7406,6 +7424,12 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 		goto out;
 	}
 
+	ret = btrfs_fscrypt_load_extent_info(inode, path, &found_key, em);
+	if (ret > 0)
+		ret = -EIO;
+	if (ret < 0)
+		goto out;
+
 	write_lock(&em_tree->lock);
 	ret = btrfs_add_extent_mapping(inode, &em, start, len);
 	write_unlock(&em_tree->lock);
@@ -9219,6 +9243,8 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
 				       u64 file_offset)
 {
 	struct btrfs_file_extent_item stack_fi;
+	u8 fscrypt_ctx[FSCRYPT_SET_CONTEXT_MAX_SIZE];
+	ssize_t fscrypt_context_size;
 	struct btrfs_replace_extent_info extent_info;
 	struct btrfs_trans_handle *trans = trans_in;
 	struct btrfs_path *path;
@@ -9252,6 +9278,14 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
 		return trans;
 	}
 
+	fscrypt_context_size = btrfs_fscrypt_context_for_new_extent(inode,
+								    fscrypt_info,
+								    fscrypt_ctx);
+	if (fscrypt_context_size < 0) {
+		ret = (int)fscrypt_context_size;
+		goto free_qgroup;
+	}
+
 	extent_info.disk_offset = start;
 	extent_info.disk_len = len;
 	extent_info.data_offset = 0;
@@ -9262,6 +9296,8 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
 	extent_info.update_times = true;
 	extent_info.qgroup_reserved = qgroup_released;
 	extent_info.insertions = 0;
+	extent_info.fscrypt_ctx = fscrypt_ctx;
+	extent_info.fscrypt_context_size = fscrypt_context_size;
 
 	path = btrfs_alloc_path();
 	if (!path) {
diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index 314cb95ba846..8e8d2f3c4c0a 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -376,7 +376,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 		struct btrfs_key new_key;
 		u64 disko = 0, diskl = 0;
 		u64 datao = 0, datal = 0;
-		u8 comp;
+		u8 comp, encryption;
 		u64 drop_start;
 
 		/* Note the key will change type as we walk through the tree */
@@ -419,6 +419,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 		extent = btrfs_item_ptr(leaf, slot,
 					struct btrfs_file_extent_item);
 		extent_gen = btrfs_file_extent_generation(leaf, extent);
+		encryption = btrfs_file_extent_encryption(leaf, extent);
 		comp = btrfs_file_extent_compression(leaf, extent);
 		type = btrfs_file_extent_type(leaf, extent);
 		if (type == BTRFS_FILE_EXTENT_REG ||
@@ -478,6 +479,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 		if (type == BTRFS_FILE_EXTENT_REG ||
 		    type == BTRFS_FILE_EXTENT_PREALLOC) {
 			struct btrfs_replace_extent_info clone_info;
+			u8 fscrypt_ctx[FSCRYPT_SET_CONTEXT_MAX_SIZE];
 
 			/*
 			 *    a  | --- range to clone ---|  b
@@ -494,6 +496,43 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 				datal -= off - key.offset;
 			}
 
+			if (encryption == BTRFS_ENCRYPTION_FSCRYPT) {
+				unsigned long offset;
+
+				key.type = BTRFS_FSCRYPT_CTX_KEY;
+				ret = btrfs_search_slot(NULL, BTRFS_I(src)->root, &key, path, 0, 0);
+				if (ret < 0)
+					goto out;
+				leaf = path->nodes[0];
+				slot = path->slots[0];
+				if (ret) {
+					btrfs_err(leaf->fs_info,
+	"missing or error searching encryption context item in leaf: root=%llu block=%llu slot=%d ino=%llu file_offset=%llu, err %i",
+						btrfs_header_owner(leaf),
+						btrfs_header_bytenr(leaf), slot,
+						key.objectid, key.offset, ret);
+					goto out;
+				}
+
+				size = btrfs_item_size(leaf, slot);
+				if (size > FSCRYPT_SET_CONTEXT_MAX_SIZE) {
+					btrfs_err(leaf->fs_info,
+	"unexpected or corrupted encryption context size in leaf: root=%llu block=%llu slot=%d ino=%llu file_offset=%llu, size %u (too big)",
+						btrfs_header_owner(leaf),
+						btrfs_header_bytenr(leaf), slot,
+						key.objectid, key.offset, size);
+					ret = -EIO;
+					goto out;
+				}
+
+				offset = btrfs_item_ptr_offset(leaf, slot),
+				read_extent_buffer(leaf, fscrypt_ctx, offset, size);
+				btrfs_release_path(path);
+				key.type = BTRFS_EXTENT_DATA_KEY;
+			} else {
+				size = 0;
+			}
+
 			clone_info.disk_offset = disko;
 			clone_info.disk_len = diskl;
 			clone_info.data_offset = datao;
@@ -502,6 +541,8 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 			clone_info.extent_buf = buf;
 			clone_info.is_new_extent = false;
 			clone_info.update_times = !no_time_update;
+			clone_info.fscrypt_ctx = fscrypt_ctx;
+			clone_info.fscrypt_context_size = size;
 			ret = btrfs_replace_file_extents(BTRFS_I(inode), path,
 					drop_start, new_key.offset + datal - 1,
 					&clone_info, &trans);
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 43b1470ebf71..0d01e31a4592 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -30,6 +30,7 @@
 #include "print-tree.h"
 #include "tree-checker.h"
 #include "delayed-inode.h"
+#include "fscrypt.h"
 
 #define MAX_CONFLICT_INODES 10
 
@@ -5118,6 +5119,8 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 	struct btrfs_file_extent_item fi = { 0 };
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
+	u8 fscrypt_ctx[FSCRYPT_SET_CONTEXT_MAX_SIZE];
+	ssize_t fscrypt_context_size;
 	enum btrfs_compression_type compress_type;
 	u64 extent_offset = em->offset;
 	u64 block_start = btrfs_extent_map_block_start(em);
@@ -5125,6 +5128,12 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 	int ret;
 	u8 encryption = btrfs_extent_map_encryption(em);
 
+	fscrypt_context_size = btrfs_fscrypt_context_for_new_extent(inode,
+								    em->fscrypt_info,
+								    fscrypt_ctx);
+	if (fscrypt_context_size < 0)
+		return (int)fscrypt_context_size;
+
 	btrfs_set_stack_file_extent_generation(&fi, trans->transid);
 	if (em->flags & EXTENT_FLAG_PREALLOC)
 		btrfs_set_stack_file_extent_type(&fi, BTRFS_FILE_EXTENT_PREALLOC);
@@ -5188,6 +5197,16 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 
 	btrfs_release_path(path);
 
+	if (fscrypt_context_size) {
+		key.objectid = btrfs_ino(inode);
+		key.type = BTRFS_FSCRYPT_CTX_KEY;
+		key.offset = em->start;
+		ret = btrfs_insert_empty_item(trans, log, path, &key, fscrypt_context_size);
+		if (ret)
+			return ret;
+		btrfs_fscrypt_save_extent_info(path, fscrypt_ctx, fscrypt_context_size);
+	}
+
 	return ret;
 }
 
-- 
2.51.0

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