diff mbox series

[v3,1/5] btrfs: add compat_flags to btrfs_inode_item

Message ID 7fd3068c977de9dd25eb98fa2b9d3cd928613138.1617900170.git.boris@bur.io (mailing list archive)
State New
Headers show
Series btrfs: support fsverity | expand

Commit Message

Boris Burkov April 8, 2021, 6:33 p.m. UTC
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(-)

Comments

Anand Jain April 8, 2021, 11:40 p.m. UTC | #1
On 09/04/2021 02:33, Boris Burkov wrote:
> 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.

I don't see an incompt flags check during mount, how does this patch 
will handle if you mount a disk with an older on-disk btrfs_inode_item 
data structure which has no compat_flags?

Why not update the tree checker (need to fix stable kernel as well) and 
inode flags, so that we spare u64 space in the btrfs_inode_item?

Also, I think we need the incompt flags to check during mount.

Thanks, Anand


> 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 c652e19ad74e..e8dbc8e848ce 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 f2fd73e58ee6..d633c563164b 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1754,6 +1754,7 @@ 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,
> @@ -1771,6 +1772,7 @@ 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 1a88f6214ebc..ef4e0265dbe3 100644
> --- a/fs/btrfs/delayed-inode.c
> +++ b/fs/btrfs/delayed-inode.c
> @@ -1718,6 +1718,7 @@ 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,
> @@ -1776,6 +1777,7 @@ 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 1e0e20ad25e4..3aa96ec27045 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);
>   }
>   
> @@ -8859,6 +8861,7 @@ 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 3415a9f06c81..2c9cbd2642b1 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)
>   
>   	btrfs_inode_lock(inode, 0);
>   	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 72c4b66ed516..fed638f995ba 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -3944,6 +3944,7 @@ 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;
>
Boris Burkov April 9, 2021, 6:20 p.m. UTC | #2
On Fri, Apr 09, 2021 at 07:40:44AM +0800, Anand Jain wrote:
> On 09/04/2021 02:33, Boris Burkov wrote:
> > 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.
> 
> I don't see an incompt flags check during mount, how does this patch will
> handle if you mount a disk with an older on-disk btrfs_inode_item data
> structure which has no compat_flags?

I'm referring to check_inode_item in fs/btrfs/tree-checker.c
Specificall, the last check it does that fails with the string: "unknown
flags detected".

This patch ignores the new compat_flags from a checking perspective, so
it won't complain no matter what an old on-disk format put there. As far
as I can tell from inspecting the code and mkfs, it should be zero,
though I suppose it's possible an older version of btrfs did not zero
it. I think the worst case would be if it weren't zero and we
incorrectly interpreted the file as having a compat_flags flag set.

> 
> Why not update the tree checker (need to fix stable kernel as well) and
> inode flags, so that we spare u64 space in the btrfs_inode_item?

I don't understand this suggestion, could you be more specific?

> 
> Also, I think we need the incompt flags to check during mount.

Same for this one, sorry. What do you think I should check?

> 
> Thanks, Anand

Thank you for the review,
Boris
> 
> 
> > 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 c652e19ad74e..e8dbc8e848ce 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 f2fd73e58ee6..d633c563164b 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -1754,6 +1754,7 @@ 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,
> > @@ -1771,6 +1772,7 @@ 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 1a88f6214ebc..ef4e0265dbe3 100644
> > --- a/fs/btrfs/delayed-inode.c
> > +++ b/fs/btrfs/delayed-inode.c
> > @@ -1718,6 +1718,7 @@ 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,
> > @@ -1776,6 +1777,7 @@ 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 1e0e20ad25e4..3aa96ec27045 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);
> >   }
> > @@ -8859,6 +8861,7 @@ 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 3415a9f06c81..2c9cbd2642b1 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)
> >   	btrfs_inode_lock(inode, 0);
> >   	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 72c4b66ed516..fed638f995ba 100644
> > --- a/fs/btrfs/tree-log.c
> > +++ b/fs/btrfs/tree-log.c
> > @@ -3944,6 +3944,7 @@ 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;
> > 
>
diff mbox series

Patch

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index c652e19ad74e..e8dbc8e848ce 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 f2fd73e58ee6..d633c563164b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1754,6 +1754,7 @@  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,
@@ -1771,6 +1772,7 @@  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 1a88f6214ebc..ef4e0265dbe3 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1718,6 +1718,7 @@  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,
@@ -1776,6 +1777,7 @@  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 1e0e20ad25e4..3aa96ec27045 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);
 }
 
@@ -8859,6 +8861,7 @@  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 3415a9f06c81..2c9cbd2642b1 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)
 
 	btrfs_inode_lock(inode, 0);
 	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 72c4b66ed516..fed638f995ba 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3944,6 +3944,7 @@  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;