All of lore.kernel.org
 help / color / mirror / Atom feed
From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 8/8] xfs: cache unlinked pointers in an rhashtable
Date: Sat, 2 Feb 2019 09:01:10 -0800	[thread overview]
Message-ID: <20190202170110.GB18160@infradead.org> (raw)
In-Reply-To: <154897672012.26065.1375987197453969157.stgit@magnolia>

On Thu, Jan 31, 2019 at 03:18:40PM -0800, Darrick J. Wong wrote:
> +/*
> + * Faster In-Core Unlinked List Lookups
> + * ====================================

I'd drop the "Faster " here - the whole point of a separate in-core
lookup is generally that it is faster.

> +struct xfs_iunlink_key {
> +	xfs_agino_t		iu_next_unlinked;
> +};

I don't think we need this structure at all.  We can just directly
pass a pointer to the xfs_agino_t instead.

> +	.obj_cmpfn		= _xfs_iunlink_obj_cmp,

No real need for the _ prefix.  Also it would generally be nice
if the method implementation name is prefix + method name.

> +int
> +xfs_iunlink_lookup_backref(
> +	struct xfs_perag	*pag,
> +	xfs_agino_t		agino,
> +	xfs_agino_t		*prev_agino)
> +{
> +	struct xfs_iunlink_key	key = { .iu_next_unlinked = agino };
> +	struct xfs_iunlink	*iu;
> +
> +	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &key,
> +			xfs_iunlink_hash_params);
> +	if (!iu)
> +		return -ENOENT;
> +	*prev_agino = iu->iu_agino;
> +	return 0;

I think we can just retun the xfs_agino_t as the return value, with
NULLAGINO as the not found return value.

> +
> +/* Forget that X.next_unlinked = @agino. */
> +int
> +xfs_iunlink_forget_backref(
> +	struct xfs_perag	*pag,
> +	xfs_agino_t		agino)
> +{
> +	struct xfs_iunlink_key	key = { .iu_next_unlinked = agino };
> +	struct xfs_iunlink	*iu;
> +	int			error;
> +
> +	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &key,
> +			xfs_iunlink_hash_params);
> +	if (!iu)
> +		return -ENOENT;
> +
> +	error = rhashtable_remove_fast(&pag->pagi_unlinked_hash,
> +			&iu->iu_rhash_head, xfs_iunlink_hash_params);
> +	if (error)
> +		return error;
> +
> +	kmem_free(iu);
> +	return 0;

This mostly duplicates the change_backref help.  If we just free
the iu for a NULLAGINO next_unlinked there we can merge the two
functions easily.

> +int xfs_iunlink_init(struct xfs_perag *pag);
> +void xfs_iunlink_destroy(struct xfs_perag *pag);
> +int xfs_iunlink_lookup_backref(struct xfs_perag *pag, xfs_agino_t agino,
> +		xfs_agino_t *prev_agino);
> +int xfs_iunlink_add_backref(struct xfs_perag *pag, xfs_agino_t prev_agino,
> +		xfs_agino_t this_agino);
> +int xfs_iunlink_forget_backref(struct xfs_perag *pag, xfs_agino_t agino);
> +int xfs_iunlink_change_backref(struct xfs_perag *pag, xfs_agino_t prev_agino,
> +		xfs_agino_t this_agino);

Half of these aren't used outside xfs_inode.c.

> +		xfs_iunlink_destroy(pag);
>  		mutex_destroy(&pag->pagi_unlinked_lock);
>  		xfs_buf_hash_destroy(pag);
>  		mutex_destroy(&pag->pag_ici_reclaim_lock);
> @@ -231,6 +232,9 @@ xfs_initialize_perag(
>  		if (first_initialised == NULLAGNUMBER)
>  			first_initialised = index;
>  		mutex_init(&pag->pagi_unlinked_lock);
> +		error = xfs_iunlink_init(pag);
> +		if (error)
> +			goto out_iunlink_mutex;

Any good reason pagi_unlinked_lock isn't handled in
xfs_iunlink_init / xfs_iunlink_destroy?

Untested patch for most of my comments above:

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index e797b11ad842..f8da8ce48348 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1907,7 +1907,7 @@ xfs_inactive(
 }
 
 /*
- * Faster In-Core Unlinked List Lookups
+ * In-Core Unlinked List Lookups
  * ====================================
  *
  * Every inode is supposed to be reachable from some other piece of metadata
@@ -1937,20 +1937,16 @@ struct xfs_iunlink {
 	xfs_agino_t		iu_next_unlinked;
 };
 
-struct xfs_iunlink_key {
-	xfs_agino_t		iu_next_unlinked;
-};
-
 /* Unlinked list predecessor lookup hashtable construction */
 static int
-xfs_iunlink_obj_cmp(
+xfs_iunlink_obj_cmpfn(
 	struct rhashtable_compare_arg	*arg,
 	const void			*obj)
 {
-	const struct xfs_iunlink_key	*key = arg->key;
+	const xfs_agino_t		*key = arg->key;
 	const struct xfs_iunlink	*iu = obj;
 
-	if (iu->iu_next_unlinked != key->iu_next_unlinked)
+	if (iu->iu_next_unlinked != *key)
 		return 1;
 	return 0;
 }
@@ -1962,28 +1958,25 @@ static const struct rhashtable_params xfs_iunlink_hash_params = {
 	.key_offset		= offsetof(struct xfs_iunlink, iu_next_unlinked),
 	.head_offset		= offsetof(struct xfs_iunlink, iu_rhash_head),
 	.automatic_shrinking	= true,
-	.obj_cmpfn		= xfs_iunlink_obj_cmp,
+	.obj_cmpfn		= xfs_iunlink_obj_cmpfn,
 };
 
 /*
- * Return X (in @prev_agino), where X.next_unlinked == @agino.  Returns -ENOENT
- * if no such relation is found.
+ * Return X, where X.next_unlinked == @agino.  Returns NULLAGINO if no such
+ * relation is found.
  */
-static int
+static xfs_agino_t
 xfs_iunlink_lookup_backref(
 	struct xfs_perag	*pag,
-	xfs_agino_t		agino,
-	xfs_agino_t		*prev_agino)
+	xfs_agino_t		agino)
 {
-	struct xfs_iunlink_key	key = { .iu_next_unlinked = agino };
 	struct xfs_iunlink	*iu;
 
-	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &key,
+	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino,
 			xfs_iunlink_hash_params);
 	if (!iu)
-		return -ENOENT;
-	*prev_agino = iu->iu_agino;
-	return 0;
+		return NULLAGINO;
+	return iu->iu_agino;
 }
 
 /* Remember that @prev_agino.next_unlinked = @this_agino. */
@@ -2003,31 +1996,6 @@ xfs_iunlink_add_backref(
 			&iu->iu_rhash_head, xfs_iunlink_hash_params);
 }
 
-/* Forget that X.next_unlinked = @agino. */
-static int
-xfs_iunlink_forget_backref(
-	struct xfs_perag	*pag,
-	xfs_agino_t		agino)
-{
-	struct xfs_iunlink_key	key = { .iu_next_unlinked = agino };
-	struct xfs_iunlink	*iu;
-	int			error;
-
-	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &key,
-			xfs_iunlink_hash_params);
-	if (!iu)
-		return -ENOENT;
-
-	error = rhashtable_remove_fast(&pag->pagi_unlinked_hash,
-			&iu->iu_rhash_head, xfs_iunlink_hash_params);
-	if (error)
-		return error;
-
-	kmem_free(iu);
-	return 0;
-}
-
-
 /* Replace X.next_unlinked = @agino with X.next_unlinked = @next_unlinked. */
 static int
 xfs_iunlink_change_backref(
@@ -2035,11 +2003,10 @@ xfs_iunlink_change_backref(
 	xfs_agino_t		agino,
 	xfs_agino_t		next_unlinked)
 {
-	struct xfs_iunlink_key	key = { .iu_next_unlinked = agino };
 	struct xfs_iunlink	*iu;
 	int			error;
 
-	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &key,
+	iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino,
 			xfs_iunlink_hash_params);
 	if (!iu)
 		return -ENOENT;
@@ -2049,8 +2016,18 @@ xfs_iunlink_change_backref(
 	if (error)
 		return error;
 
-	iu->iu_next_unlinked = next_unlinked;
+	/*
+	 * If there is no new next entry just free our item and return.
+	 */
+	if (next_unlinked == NULLAGINO) {
+		kmem_free(iu);
+		return 0;
+	}
 
+	/*
+	 * Else update the hash table to the new entry.
+	 */
+	iu->iu_next_unlinked = next_unlinked;
 	return rhashtable_insert_fast(&pag->pagi_unlinked_hash,
 			&iu->iu_rhash_head, xfs_iunlink_hash_params);
 }
@@ -2357,8 +2334,8 @@ xfs_iunlink_map_prev(
 	ASSERT(head_agino != target_agino);
 
 	/* See if our backref cache can find it faster. */
-	error = xfs_iunlink_lookup_backref(pag, target_agino, &next_agino);
-	if (error == 0) {
+	next_agino = xfs_iunlink_lookup_backref(pag, target_agino);
+	if (next_agino != NULLAGINO) {
 		next_ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, next_agino);
 		error = xfs_iunlink_map_ino(tp, next_ino, &last_imap,
 				&last_dip, &last_ibp);
@@ -2468,7 +2445,8 @@ xfs_iunlink_remove(
 			goto out_unlock;
 
 		if (next_agino != NULLAGINO) {
-			error = xfs_iunlink_forget_backref(pag, next_agino);
+			error = xfs_iunlink_change_backref(pag, next_agino,
+					NULLAGINO);
 			if (error)
 				goto out_unlock;
 		}
@@ -2496,7 +2474,8 @@ xfs_iunlink_remove(
 		if (error)
 			goto out_unlock;
 		if (next_agino != NULLAGINO) {
-			error = xfs_iunlink_forget_backref(pag, next_agino);
+			error = xfs_iunlink_change_backref(pag, next_agino,
+					NULLAGINO);
 			if (error)
 				goto out_unlock;
 		}
@@ -2504,11 +2483,7 @@ xfs_iunlink_remove(
 		/* Point the previous inode on the list to the next inode. */
 		xfs_iunlink_update_dinode(tp, last_ibp, last_dip, &imap,
 				next_ino, next_agino);
-		if (next_agino == NULLAGINO)
-			error = xfs_iunlink_forget_backref(pag, agino);
-		else
-			error = xfs_iunlink_change_backref(pag, agino,
-					next_agino);
+		error = xfs_iunlink_change_backref(pag, agino, next_agino);
 		if (error)
 			goto out_unlock;
 	}

  parent reply	other threads:[~2019-02-02 17:01 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-31 23:17 [PATCH 0/8] xfs: incore unlinked list Darrick J. Wong
2019-01-31 23:17 ` [PATCH 1/8] xfs: clean up iunlink functions Darrick J. Wong
2019-02-01  8:01   ` Christoph Hellwig
2019-02-02 19:15     ` Darrick J. Wong
2019-01-31 23:18 ` [PATCH 2/8] xfs: track unlinked inode counts in per-ag data Darrick J. Wong
2019-02-01 18:59   ` Brian Foster
2019-02-01 19:33     ` Darrick J. Wong
2019-02-02 16:14       ` Christoph Hellwig
2019-02-02 19:28         ` Darrick J. Wong
2019-01-31 23:18 ` [PATCH 3/8] xfs: refactor AGI unlinked bucket updates Darrick J. Wong
2019-02-01 19:00   ` Brian Foster
2019-02-02 19:50     ` Darrick J. Wong
2019-02-02 16:21   ` Christoph Hellwig
2019-02-02 19:51     ` Darrick J. Wong
2019-01-31 23:18 ` [PATCH 4/8] xfs: strengthen AGI unlinked inode bucket pointer checks Darrick J. Wong
2019-02-01 19:00   ` Brian Foster
2019-02-02 16:22   ` Christoph Hellwig
2019-01-31 23:18 ` [PATCH 5/8] xfs: refactor inode unlinked pointer update functions Darrick J. Wong
2019-02-01 19:01   ` Brian Foster
2019-02-02 22:00     ` Darrick J. Wong
2019-02-02 16:27   ` Christoph Hellwig
2019-02-02 20:29     ` Darrick J. Wong
2019-01-31 23:18 ` [PATCH 6/8] xfs: hoist unlinked list search and mapping to a separate function Darrick J. Wong
2019-02-01 19:01   ` Brian Foster
2019-02-02 20:46     ` Darrick J. Wong
2019-02-04 13:18       ` Brian Foster
2019-02-04 16:31         ` Darrick J. Wong
2019-02-02 16:30   ` Christoph Hellwig
2019-02-02 20:42     ` Darrick J. Wong
2019-02-02 16:51   ` Christoph Hellwig
2019-01-31 23:18 ` [PATCH 7/8] xfs: add tracepoints for high level iunlink operations Darrick J. Wong
2019-02-01 19:01   ` Brian Foster
2019-02-01 19:14     ` Darrick J. Wong
2019-01-31 23:18 ` [PATCH 8/8] xfs: cache unlinked pointers in an rhashtable Darrick J. Wong
2019-02-01  8:03   ` Christoph Hellwig
2019-02-01 23:59     ` Dave Chinner
2019-02-02  4:31       ` Darrick J. Wong
2019-02-02 16:07         ` Christoph Hellwig
2019-02-01 19:29   ` Brian Foster
2019-02-01 19:40     ` Darrick J. Wong
2019-02-02 17:01   ` Christoph Hellwig [this message]
2019-02-01  7:57 ` [PATCH 0/8] xfs: incore unlinked list Christoph Hellwig

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190202170110.GB18160@infradead.org \
    --to=hch@infradead.org \
    --cc=darrick.wong@oracle.com \
    --cc=linux-xfs@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.