On Fri, May 18, 2018 at 06:01:22PM +0200, Miklos Szeredi wrote:
> On Fri, May 18, 2018 at 5:40 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> > On Fri, May 18, 2018 at 05:11:20PM +0200, Miklos Szeredi wrote:
> >> On Fri, May 18, 2018 at 5:03 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> >> > Mind explaining what the hell is wrong with insert_inode_locked4()?
> >>
> >> That it doesn't return the old inode if found.
> >>
> >> Btw, these functions are eerily similar, and it'd be nice to reduce
> >> the number of them.
How about this one?
Same thing could be done with iget_locked()/insert_inode_locked(), but I also
wonder how much optimization do the "fast" versions get for lack of a get()
function... Shouldn't we use the generic ones for the all cases?
Thanks,
Miklos
---
From: Miklos Szeredi <miklos@xxxxxxxxxx>
Date: Thu, 17 May 2018 10:53:05 +0200
Subject: vfs: factor out inode_insert5()
Split out common helper for race free insertion of an already allocated
inode into the cache. Use this from iget5_locked() and
insert_inode_locked4(). Make iget5_locked() use new_inode()/iput() instead
of alloc_inode()/destroy_inode() directly.
Also export to modules for use by filesystems which want to preallocate an
inode before file/directory creation.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/inode.c | 164 ++++++++++++++++++++++++-----------------------------
include/linux/fs.h | 4 +
2 files changed, 79 insertions(+), 89 deletions(-)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1003,6 +1003,70 @@ void unlock_two_nondirectories(struct in
EXPORT_SYMBOL(unlock_two_nondirectories);
/**
+ * inode_insert5 - obtain an inode from a mounted file system
+ * @inode: pre-allocated inode to use for insert to cache
+ * @hashval: hash value (usually inode number) to get
+ * @test: callback used for comparisons between inodes
+ * @set: callback used to initialize a new struct inode
+ * @data: opaque data pointer to pass to @test and @set
+ *
+ * Search for the inode specified by @hashval and @data in the inode cache,
+ * and if present it is return it with an increased reference count. This is
+ * a variant of iget5_locked() for callers that don't want to fail on memory
+ * allocation of inode.
+ *
+ * If the inode is not in cache, insert the pre-allocated inode to cache and
+ * return it locked, hashed, and with the I_NEW flag set. The file system gets
+ * to fill it in before unlocking it via unlock_new_inode().
+ *
+ * Note both @test and @set are called with the inode_hash_lock held, so can't
+ * sleep.
+ */
+struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
+ int (*test)(struct inode *, void *),
+ int (*set)(struct inode *, void *), void *data)
+{
+ struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
+ struct inode *old;
+
+again:
+ spin_lock(&inode_hash_lock);
+ old = find_inode(inode->i_sb, head, test, data);
+ if (unlikely(old)) {
+ /*
+ * Uhhuh, somebody else created the same inode under us.
+ * Use the old inode instead of the preallocated one.
+ */
+ spin_unlock(&inode_hash_lock);
+ wait_on_inode(old);
+ if (unlikely(inode_unhashed(old))) {
+ iput(old);
+ goto again;
+ }
+ return old;
+ }
+
+ if (set && unlikely(set(inode, data))) {
+ inode = NULL;
+ goto unlock;
+ }
+
+ /*
+ * Return the locked inode with I_NEW set, the
+ * caller is responsible for filling in the contents
+ */
+ spin_lock(&inode->i_lock);
+ inode->i_state |= I_NEW;
+ hlist_add_head(&inode->i_hash, head);
+ spin_unlock(&inode->i_lock);
+unlock:
+ spin_unlock(&inode_hash_lock);
+
+ return inode;
+}
+EXPORT_SYMBOL(inode_insert5);
+
+/**
* iget5_locked - obtain an inode from a mounted file system
* @sb: super block of file system
* @hashval: hash value (usually inode number) to get
@@ -1026,66 +1090,18 @@ struct inode *iget5_locked(struct super_
int (*test)(struct inode *, void *),
int (*set)(struct inode *, void *), void *data)
{
- struct hlist_head *head = inode_hashtable + hash(sb, hashval);
- struct inode *inode;
-again:
- spin_lock(&inode_hash_lock);
- inode = find_inode(sb, head, test, data);
- spin_unlock(&inode_hash_lock);
-
- if (inode) {
- wait_on_inode(inode);
- if (unlikely(inode_unhashed(inode))) {
- iput(inode);
- goto again;
- }
- return inode;
- }
+ struct inode *inode = ilookup5(sb, hashval, test, data);
- inode = alloc_inode(sb);
- if (inode) {
- struct inode *old;
+ if (!inode) {
+ struct inode *new = new_inode(sb);
- spin_lock(&inode_hash_lock);
- /* We released the lock, so.. */
- old = find_inode(sb, head, test, data);
- if (!old) {
- if (set(inode, data))
- goto set_failed;
-
- spin_lock(&inode->i_lock);
- inode->i_state = I_NEW;
- hlist_add_head(&inode->i_hash, head);
- spin_unlock(&inode->i_lock);
- inode_sb_list_add(inode);
- spin_unlock(&inode_hash_lock);
-
- /* Return the locked inode with I_NEW set, the
- * caller is responsible for filling in the contents
- */
- return inode;
- }
-
- /*
- * Uhhuh, somebody else created the same inode under
- * us. Use the old inode instead of the one we just
- * allocated.
- */
- spin_unlock(&inode_hash_lock);
- destroy_inode(inode);
- inode = old;
- wait_on_inode(inode);
- if (unlikely(inode_unhashed(inode))) {
- iput(inode);
- goto again;
+ if (new) {
+ inode = inode_insert5(new, hashval, test, set, data);
+ if (unlikely(inode != new))
+ iput(new);
}
}
return inode;
-
-set_failed:
- spin_unlock(&inode_hash_lock);
- destroy_inode(inode);
- return NULL;
}
EXPORT_SYMBOL(iget5_locked);
@@ -1426,43 +1442,13 @@ EXPORT_SYMBOL(insert_inode_locked);
int insert_inode_locked4(struct inode *inode, unsigned long hashval,
int (*test)(struct inode *, void *), void *data)
{
- struct super_block *sb = inode->i_sb;
- struct hlist_head *head = inode_hashtable + hash(sb, hashval);
+ struct inode *old = inode_insert5(inode, hashval, test, NULL, data);
- while (1) {
- struct inode *old = NULL;
-
- spin_lock(&inode_hash_lock);
- hlist_for_each_entry(old, head, i_hash) {
- if (old->i_sb != sb)
- continue;
- if (!test(old, data))
- continue;
- spin_lock(&old->i_lock);
- if (old->i_state & (I_FREEING|I_WILL_FREE)) {
- spin_unlock(&old->i_lock);
- continue;
- }
- break;
- }
- if (likely(!old)) {
- spin_lock(&inode->i_lock);
- inode->i_state |= I_NEW;
- hlist_add_head(&inode->i_hash, head);
- spin_unlock(&inode->i_lock);
- spin_unlock(&inode_hash_lock);
- return 0;
- }
- __iget(old);
- spin_unlock(&old->i_lock);
- spin_unlock(&inode_hash_lock);
- wait_on_inode(old);
- if (unlikely(!inode_unhashed(old))) {
- iput(old);
- return -EBUSY;
- }
+ if (old != inode) {
iput(old);
+ return -EBUSY;
}
+ return 0;
}
EXPORT_SYMBOL(insert_inode_locked4);
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2879,6 +2879,10 @@ extern struct inode *ilookup5(struct sup
int (*test)(struct inode *, void *), void *data);
extern struct inode *ilookup(struct super_block *sb, unsigned long ino);
+extern struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
+ int (*test)(struct inode *, void *),
+ int (*set)(struct inode *, void *),
+ void *data);
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 *,
--
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