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new primitive: discard_new_inode()

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We don't want open-by-handle picking half-set-up in-core
struct inode from e.g. mkdir() having failed halfway through.
In other words, we don't want such inodes returned by iget_locked()
on their way to extinction.  However, we can't just have them
unhashed - otherwise open-by-handle immediately *after* that would've
ended up creating a new in-core inode over the on-disk one that
is in process of being freed right under us.

	Solution: new flag (I_CREATING) set by insert_inode_locked() and
removed by unlock_new_inode() and a new primitive (discard_new_inode())
to be used by such halfway-through-setup failure exits instead of
unlock_new_inode() / iput() combinations.  That primitive unlocks new
inode, but leaves I_CREATING in place.

	iget_locked() treats finding an I_CREATING inode as failure
(-ESTALE, once we sort out the error propagation).
	insert_inode_locked() treats the same as instant -EBUSY.
	ilookup() treats those as icache miss.

[Fix by Dan Carpenter <dan.carpenter@oracle.com> folded in]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-06-28 15:53:17 -04:00
parent c971e6a006
commit c2b6d621c4
3 changed files with 47 additions and 6 deletions
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6
include/linux/fs.h
View file

@ -2016,6 +2016,8 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
* I_OVL_INUSE Used by overlayfs to get exclusive ownership on upper
* and work dirs among overlayfs mounts.
*
* I_CREATING New object's inode in the middle of setting up.
*
* Q: What is the difference between I_WILL_FREE and I_FREEING?
*/
#define I_DIRTY_SYNC (1 << 0)
@ -2036,7 +2038,8 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
#define __I_DIRTY_TIME_EXPIRED 12
#define I_DIRTY_TIME_EXPIRED (1 << __I_DIRTY_TIME_EXPIRED)
#define I_WB_SWITCH (1 << 13)
#define I_OVL_INUSE (1 << 14)
#define I_OVL_INUSE (1 << 14)
#define I_CREATING (1 << 15)
#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
#define I_DIRTY (I_DIRTY_INODE | I_DIRTY_PAGES)
@ -2919,6 +2922,7 @@ extern void lockdep_annotate_inode_mutex_key(struct inode *inode);
static inline void lockdep_annotate_inode_mutex_key(struct inode *inode) { };
#endif
extern void unlock_new_inode(struct inode *);
extern void discard_new_inode(struct inode *);
extern unsigned int get_next_ino(void);
extern void evict_inodes(struct super_block *sb);