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fs: make plain ->i_state access fail to compile

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... to make sure all accesses are properly validated.

Merely renaming the var to __i_state still lets the compiler make the
following suggestion:
error: 'struct inode' has no member named 'i_state'; did you mean '__i_state'?

Unfortunately some people will add the __'s and call it a day.

In order to make it harder to mess up in this way, hide it behind a
struct. The resulting error message should be convincing in terms of
checking what to do:
error: invalid operands to binary & (have 'struct inode_state_flags' and 'int')

Of course people determined to do a plain access can still do it, but
nothing can be done for that case.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Mateusz Guzik 2025-10-09 09:59:28 +02:00 committed by Christian Brauner
parent 18c61399f6
commit 2ed81b4bef
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 14 additions and 7 deletions
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21
include/linux/fs.h
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@ -785,6 +785,13 @@ enum inode_state_flags_enum {
#define I_DIRTY (I_DIRTY_INODE | I_DIRTY_PAGES)
#define I_DIRTY_ALL (I_DIRTY | I_DIRTY_TIME)
/*
* Use inode_state_read() & friends to access.
*/
struct inode_state_flags {
enum inode_state_flags_enum __state;
};
/*
* Keep mostly read-only and often accessed (especially for
* the RCU path lookup and 'stat' data) fields at the beginning
@ -843,7 +850,7 @@ struct inode {
#endif
/* Misc */
enum inode_state_flags_enum i_state;
struct inode_state_flags i_state;
/* 32-bit hole */
struct rw_semaphore i_rwsem;
@ -909,19 +916,19 @@ struct inode {
*/
static inline enum inode_state_flags_enum inode_state_read_once(struct inode *inode)
{
return READ_ONCE(inode->i_state);
return READ_ONCE(inode->i_state.__state);
}
static inline enum inode_state_flags_enum inode_state_read(struct inode *inode)
{
lockdep_assert_held(&inode->i_lock);
return inode->i_state;
return inode->i_state.__state;
}
static inline void inode_state_set_raw(struct inode *inode,
enum inode_state_flags_enum flags)
{
WRITE_ONCE(inode->i_state, inode->i_state | flags);
WRITE_ONCE(inode->i_state.__state, inode->i_state.__state | flags);
}
static inline void inode_state_set(struct inode *inode,
@ -934,7 +941,7 @@ static inline void inode_state_set(struct inode *inode,
static inline void inode_state_clear_raw(struct inode *inode,
enum inode_state_flags_enum flags)
{
WRITE_ONCE(inode->i_state, inode->i_state & ~flags);
WRITE_ONCE(inode->i_state.__state, inode->i_state.__state & ~flags);
}
static inline void inode_state_clear(struct inode *inode,
@ -947,7 +954,7 @@ static inline void inode_state_clear(struct inode *inode,
static inline void inode_state_assign_raw(struct inode *inode,
enum inode_state_flags_enum flags)
{
WRITE_ONCE(inode->i_state, flags);
WRITE_ONCE(inode->i_state.__state, flags);
}
static inline void inode_state_assign(struct inode *inode,
@ -962,7 +969,7 @@ static inline void inode_state_replace_raw(struct inode *inode,
enum inode_state_flags_enum setflags)
{
enum inode_state_flags_enum flags;
flags = inode->i_state;
flags = inode->i_state.__state;
flags &= ~clearflags;
flags |= setflags;
inode_state_assign_raw(inode, flags);