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dentry name snapshots

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take_dentry_name_snapshot() takes a safe snapshot of dentry name;
if the name is a short one, it gets copied into caller-supplied
structure, otherwise an extra reference to external name is grabbed
(those are never modified).  In either case the pointer to stable
string is stored into the same structure.

dentry must be held by the caller of take_dentry_name_snapshot(),
but may be freely dropped afterwards - the snapshot will stay
until destroyed by release_dentry_name_snapshot().

Intended use:
	struct name_snapshot s;

	take_dentry_name_snapshot(&s, dentry);
	...
	access s.name
	...
	release_dentry_name_snapshot(&s);

Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name
to pass down with event.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2017-07-07 14:51:19 -04:00
parent a8e2b63677
commit 49d31c2f38
6 changed files with 48 additions and 42 deletions
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6
include/linux/dcache.h
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@@ -591,5 +591,11 @@ static inline struct inode *d_real_inode(const struct dentry *dentry)
return d_backing_inode(d_real((struct dentry *) dentry, NULL, 0));
}
struct name_snapshot {
const char *name;
char inline_name[DNAME_INLINE_LEN];
};
void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
void release_dentry_name_snapshot(struct name_snapshot *);
#endif /* __LINUX_DCACHE_H */