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VFS: Add a fallthrough flag for marking virtual dentries 

Add a DCACHE_FALLTHRU flag to indicate that, in a layered filesystem, this is
a virtual dentry that covers another one in a lower layer that should be used
instead.  This may be recorded on medium if directory integration is stored
there.

The flag can be set with d_set_fallthru() and tested with d_is_fallthru().

Original-author: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
David Howells 2015-01-29 12:02:28 +00:00 committed by Al Viro
parent e7f7d2253c
commit df1a085af1
2 changed files with 27 additions and 1 deletions
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19
fs/dcache.c
View File

@ -1659,6 +1659,22 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
}
EXPORT_SYMBOL(d_set_d_op);
/*
* d_set_fallthru - Mark a dentry as falling through to a lower layer
* @dentry - The dentry to mark
*
* Mark a dentry as falling through to the lower layer (as set with
* d_pin_lower()). This flag may be recorded on the medium.
*/
void d_set_fallthru(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_FALLTHRU;
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(d_set_fallthru);
static unsigned d_flags_for_inode(struct inode *inode)
{
unsigned add_flags = DCACHE_FILE_TYPE;
@ -1691,7 +1707,8 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
unsigned add_flags = d_flags_for_inode(inode);
spin_lock(&dentry->d_lock);
__d_set_type(dentry, add_flags);
dentry->d_flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
dentry->d_flags |= add_flags;
if (inode)
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
dentry->d_inode = inode;

9
include/linux/dcache.h
View File

@ -223,6 +223,7 @@ struct dentry_operations {
#define DCACHE_FILE_TYPE 0x00500000 /* Other file type (or fallthru to such) */
#define DCACHE_MAY_FREE 0x00800000
#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
extern seqlock_t rename_lock;
@ -470,6 +471,14 @@ static inline bool d_is_positive(const struct dentry *dentry)
return !d_is_negative(dentry);
}
extern void d_set_fallthru(struct dentry *dentry);
static inline bool d_is_fallthru(const struct dentry *dentry)
{
return dentry->d_flags & DCACHE_FALLTHRU;
}
extern int sysctl_vfs_cache_pressure;
static inline unsigned long vfs_pressure_ratio(unsigned long val)