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From: Boris Burkov <boris@bur.io>
To: linux-btrfs@vger.kernel.org, kernel-team@fb.com,
	linux-fscrypt@vger.kernel.org,
	'Eric Biggers ' <ebiggers@kernel.org>
Subject: [PATCH v2 1/5] btrfs: add compat_flags to btrfs_inode_item
Date: Fri,  5 Mar 2021 11:26:29 -0800
Message-ID: <f47aa729e2c15b9e3f913c4347bf24562a631772.1614971203.git.boris@bur.io> (raw)
In-Reply-To: <cover.1614971203.git.boris@bur.io>

The tree checker currently rejects unrecognized flags when it reads
btrfs_inode_item. Practically, this means that adding a new flag makes
the change backwards incompatible if the flag is ever set on a file.

Take up one of the 4 reserved u64 fields in the btrfs_inode_item as a
new "compat_flags". These flags are zero on inode creation in btrfs and
mkfs and are ignored by an older kernel, so it should be safe to use
them in this way.

Signed-off-by: Boris Burkov <boris@bur.io>
---
 fs/btrfs/btrfs_inode.h          | 1 +
 fs/btrfs/ctree.h                | 2 ++
 fs/btrfs/delayed-inode.c        | 2 ++
 fs/btrfs/inode.c                | 3 +++
 fs/btrfs/ioctl.c                | 7 ++++---
 fs/btrfs/tree-log.c             | 1 +
 include/uapi/linux/btrfs_tree.h | 7 ++++++-
 7 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 28e202e89660..8b95932f25a8 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -191,6 +191,7 @@ struct btrfs_inode {
 
 	/* flags field from the on disk inode */
 	u32 flags;
+	u64 compat_flags;
 
 	/*
 	 * Counters to keep track of the number of extent item's we may use due
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 40ec3393d2a1..e65df997a2c6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1761,6 +1761,7 @@ BTRFS_SETGET_FUNCS(inode_gid, struct btrfs_inode_item, gid, 32);
 BTRFS_SETGET_FUNCS(inode_mode, struct btrfs_inode_item, mode, 32);
 BTRFS_SETGET_FUNCS(inode_rdev, struct btrfs_inode_item, rdev, 64);
 BTRFS_SETGET_FUNCS(inode_flags, struct btrfs_inode_item, flags, 64);
+BTRFS_SETGET_FUNCS(inode_compat_flags, struct btrfs_inode_item, compat_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(stack_inode_generation, struct btrfs_inode_item,
 			 generation, 64);
 BTRFS_SETGET_STACK_FUNCS(stack_inode_sequence, struct btrfs_inode_item,
@@ -1778,6 +1779,7 @@ BTRFS_SETGET_STACK_FUNCS(stack_inode_gid, struct btrfs_inode_item, gid, 32);
 BTRFS_SETGET_STACK_FUNCS(stack_inode_mode, struct btrfs_inode_item, mode, 32);
 BTRFS_SETGET_STACK_FUNCS(stack_inode_rdev, struct btrfs_inode_item, rdev, 64);
 BTRFS_SETGET_STACK_FUNCS(stack_inode_flags, struct btrfs_inode_item, flags, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_inode_compat_flags, struct btrfs_inode_item, compat_flags, 64);
 BTRFS_SETGET_FUNCS(timespec_sec, struct btrfs_timespec, sec, 64);
 BTRFS_SETGET_FUNCS(timespec_nsec, struct btrfs_timespec, nsec, 32);
 BTRFS_SETGET_STACK_FUNCS(stack_timespec_sec, struct btrfs_timespec, sec, 64);
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index ec0b50b8c5d6..6ea9d27b9c9d 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1733,6 +1733,7 @@ static void fill_stack_inode_item(struct btrfs_trans_handle *trans,
 	btrfs_set_stack_inode_transid(inode_item, trans->transid);
 	btrfs_set_stack_inode_rdev(inode_item, inode->i_rdev);
 	btrfs_set_stack_inode_flags(inode_item, BTRFS_I(inode)->flags);
+	btrfs_set_stack_inode_compat_flags(inode_item, BTRFS_I(inode)->compat_flags);
 	btrfs_set_stack_inode_block_group(inode_item, 0);
 
 	btrfs_set_stack_timespec_sec(&inode_item->atime,
@@ -1791,6 +1792,7 @@ int btrfs_fill_inode(struct inode *inode, u32 *rdev)
 	inode->i_rdev = 0;
 	*rdev = btrfs_stack_inode_rdev(inode_item);
 	BTRFS_I(inode)->flags = btrfs_stack_inode_flags(inode_item);
+	BTRFS_I(inode)->compat_flags = btrfs_stack_inode_compat_flags(inode_item);
 
 	inode->i_atime.tv_sec = btrfs_stack_timespec_sec(&inode_item->atime);
 	inode->i_atime.tv_nsec = btrfs_stack_timespec_nsec(&inode_item->atime);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4f2f1e932751..4529e974c582 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3627,6 +3627,7 @@ static int btrfs_read_locked_inode(struct inode *inode,
 
 	BTRFS_I(inode)->index_cnt = (u64)-1;
 	BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);
+	BTRFS_I(inode)->compat_flags = btrfs_inode_compat_flags(leaf, inode_item);
 
 cache_index:
 	/*
@@ -3793,6 +3794,7 @@ static void fill_inode_item(struct btrfs_trans_handle *trans,
 	btrfs_set_token_inode_transid(&token, item, trans->transid);
 	btrfs_set_token_inode_rdev(&token, item, inode->i_rdev);
 	btrfs_set_token_inode_flags(&token, item, BTRFS_I(inode)->flags);
+	btrfs_set_token_inode_compat_flags(&token, item, BTRFS_I(inode)->compat_flags);
 	btrfs_set_token_inode_block_group(&token, item, 0);
 }
 
@@ -8844,6 +8846,7 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
 	ei->defrag_bytes = 0;
 	ei->disk_i_size = 0;
 	ei->flags = 0;
+	ei->compat_flags = 0;
 	ei->csum_bytes = 0;
 	ei->index_cnt = (u64)-1;
 	ei->dir_index = 0;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a8c60d46d19c..d3fb065312f5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -102,8 +102,9 @@ static unsigned int btrfs_mask_fsflags_for_type(struct inode *inode,
  * Export internal inode flags to the format expected by the FS_IOC_GETFLAGS
  * ioctl.
  */
-static unsigned int btrfs_inode_flags_to_fsflags(unsigned int flags)
+static unsigned int btrfs_inode_flags_to_fsflags(struct btrfs_inode *binode)
 {
+	unsigned int flags = binode->flags;
 	unsigned int iflags = 0;
 
 	if (flags & BTRFS_INODE_SYNC)
@@ -156,7 +157,7 @@ void btrfs_sync_inode_flags_to_i_flags(struct inode *inode)
 static int btrfs_ioctl_getflags(struct file *file, void __user *arg)
 {
 	struct btrfs_inode *binode = BTRFS_I(file_inode(file));
-	unsigned int flags = btrfs_inode_flags_to_fsflags(binode->flags);
+	unsigned int flags = btrfs_inode_flags_to_fsflags(binode);
 
 	if (copy_to_user(arg, &flags, sizeof(flags)))
 		return -EFAULT;
@@ -228,7 +229,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 
 	inode_lock(inode);
 	fsflags = btrfs_mask_fsflags_for_type(inode, fsflags);
-	old_fsflags = btrfs_inode_flags_to_fsflags(binode->flags);
+	old_fsflags = btrfs_inode_flags_to_fsflags(binode);
 
 	ret = vfs_ioc_setflags_prepare(inode, old_fsflags, fsflags);
 	if (ret)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 2f1acc9aea9e..c436b4517452 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3942,6 +3942,7 @@ static void fill_inode_item(struct btrfs_trans_handle *trans,
 	btrfs_set_token_inode_transid(&token, item, trans->transid);
 	btrfs_set_token_inode_rdev(&token, item, inode->i_rdev);
 	btrfs_set_token_inode_flags(&token, item, BTRFS_I(inode)->flags);
+	btrfs_set_token_inode_compat_flags(&token, item, BTRFS_I(inode)->compat_flags);
 	btrfs_set_token_inode_block_group(&token, item, 0);
 }
 
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 58d7cff9afb1..ae25280316bd 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -574,11 +574,16 @@ struct btrfs_inode_item {
 	/* modification sequence number for NFS */
 	__le64 sequence;
 
+	/*
+	 * flags which aren't checked for corruption at mount
+	 * and can be added in a backwards compatible way
+	 */
+	__le64 compat_flags;
 	/*
 	 * a little future expansion, for more than this we can
 	 * just grow the inode item and version it
 	 */
-	__le64 reserved[4];
+	__le64 reserved[3];
 	struct btrfs_timespec atime;
 	struct btrfs_timespec ctime;
 	struct btrfs_timespec mtime;
-- 
2.24.1


  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-05 19:26 [PATCH v2 0/5] btrfs: support fsverity Boris Burkov
2021-03-05 19:26 ` Boris Burkov [this message]
2021-03-15 23:07   ` [PATCH v2 1/5] btrfs: add compat_flags to btrfs_inode_item Eric Biggers
2021-03-15 23:29     ` Boris Burkov
2021-03-05 19:26 ` [PATCH v2 2/5] btrfs: initial fsverity support Boris Burkov
2021-03-07  7:13   ` kernel test robot
2021-03-15 23:17   ` Eric Biggers
2021-03-16  0:42     ` Boris Burkov
2021-03-16  0:57       ` Eric Biggers
2021-03-16 18:44   ` Eric Biggers
2021-03-05 19:26 ` [PATCH v2 3/5] btrfs: check verity for reads of inline extents and holes Boris Burkov
2021-03-05 19:26 ` [PATCH v2 4/5] btrfs: fallback to buffered io for verity files Boris Burkov
2021-03-05 19:26 ` [PATCH v2 5/5] btrfs: verity metadata orphan items Boris Burkov
2021-03-15 23:09 ` [PATCH v2 0/5] btrfs: support fsverity Eric Biggers
2021-03-15 23:47   ` Boris Burkov

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