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vfs: add find_inode_nowait() function

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Add a new function find_inode_nowait() which is an even more general
version of ilookup5_nowait().  It is designed for callers which need
very fine grained control over when the function is allowed to block
or increment the inode's reference count.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Theodore Ts'o 2015-02-02 00:37:01 -05:00 committed by Al Viro
parent 0ae45f63d4
commit fe032c422c
2 changed files with 55 additions and 0 deletions
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50
fs/inode.c
View File

@ -1284,6 +1284,56 @@ struct inode *ilookup(struct super_block *sb, unsigned long ino)
}
EXPORT_SYMBOL(ilookup);
/**
* find_inode_nowait - find an inode in the inode cache
* @sb: super block of file system to search
* @hashval: hash value (usually inode number) to search for
* @match: callback used for comparisons between inodes
* @data: opaque data pointer to pass to @match
*
* Search for the inode specified by @hashval and @data in the inode
* cache, where the helper function @match will return 0 if the inode
* does not match, 1 if the inode does match, and -1 if the search
* should be stopped. The @match function must be responsible for
* taking the i_lock spin_lock and checking i_state for an inode being
* freed or being initialized, and incrementing the reference count
* before returning 1. It also must not sleep, since it is called with
* the inode_hash_lock spinlock held.
*
* This is a even more generalized version of ilookup5() when the
* function must never block --- find_inode() can block in
* __wait_on_freeing_inode() --- or when the caller can not increment
* the reference count because the resulting iput() might cause an
* inode eviction. The tradeoff is that the @match funtion must be
* very carefully implemented.
*/
struct inode *find_inode_nowait(struct super_block *sb,
unsigned long hashval,
int (*match)(struct inode *, unsigned long,
void *),
void *data)
{
struct hlist_head *head = inode_hashtable + hash(sb, hashval);
struct inode *inode, *ret_inode = NULL;
int mval;
spin_lock(&inode_hash_lock);
hlist_for_each_entry(inode, head, i_hash) {
if (inode->i_sb != sb)
continue;
mval = match(inode, hashval, data);
if (mval == 0)
continue;
if (mval == 1)
ret_inode = inode;
goto out;
}
out:
spin_unlock(&inode_hash_lock);
return ret_inode;
}
EXPORT_SYMBOL(find_inode_nowait);
int insert_inode_locked(struct inode *inode)
{
struct super_block *sb = inode->i_sb;

5
include/linux/fs.h
View File

@ -2441,6 +2441,11 @@ extern struct inode *ilookup(struct super_block *sb, unsigned long ino);
extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
extern struct inode * iget_locked(struct super_block *, unsigned long);
extern struct inode *find_inode_nowait(struct super_block *,
unsigned long,
int (*match)(struct inode *,
unsigned long, void *),
void *data);
extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
extern int insert_inode_locked(struct inode *);
#ifdef CONFIG_DEBUG_LOCK_ALLOC