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From: "Darrick J. Wong" <djwong@kernel.org>
To: djwong@kernel.org
Cc: linux-xfs@vger.kernel.org, david@fromorbit.com, hch@infradead.org
Subject: [PATCH 06/15] xfs: separate the dqrele_all inode grab logic from xfs_inode_walk_ag_grab
Date: Wed, 02 Jun 2021 15:25:30 -0700	[thread overview]
Message-ID: <162267273023.2375284.13883230665214658106.stgit@locust> (raw)
In-Reply-To: <162267269663.2375284.15885514656776142361.stgit@locust>

From: Darrick J. Wong <djwong@kernel.org>

Disentangle the dqrele_all inode grab code from the "generic" inode walk
grabbing code, and and use the opportunity to document why the dqrele
grab function does what it does.  Since xfs_inode_walk_ag_grab is now
only used for blockgc, rename it to reflect that.

Ultimately, there will be four reasons to perform a walk of incore
inodes: quotaoff dquote releasing (dqrele), garbage collection of
speculative preallocations (blockgc), reclamation of incore inodes
(reclaim), and deferred inactivation (inodegc).  Each of these four have
their own slightly different criteria for deciding if they want to
handle an inode, so it makes more sense to have four cohesive igrab
functions than one confusing parameteric grab function like we do now.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_icache.c |   71 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 66 insertions(+), 5 deletions(-)


diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index c6d956406033..45979791313f 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -774,6 +774,44 @@ xfs_icache_inode_is_allocated(
 #define XFS_LOOKUP_BATCH	32
 
 #ifdef CONFIG_XFS_QUOTA
+/* Decide if we want to grab this inode to drop its dquots. */
+static bool
+xfs_dqrele_igrab(
+	struct xfs_inode	*ip)
+{
+	bool			ret = false;
+
+	ASSERT(rcu_read_lock_held());
+
+	/* Check for stale RCU freed inode */
+	spin_lock(&ip->i_flags_lock);
+	if (!ip->i_ino)
+		goto out_unlock;
+
+	/*
+	 * Skip inodes that are anywhere in the reclaim machinery because we
+	 * drop dquots before tagging an inode for reclamation.
+	 */
+	if (ip->i_flags & (XFS_IRECLAIM | XFS_IRECLAIMABLE))
+		goto out_unlock;
+
+	/*
+	 * The inode looks alive; try to grab a VFS reference so that it won't
+	 * get destroyed.  If we got the reference, return true to say that
+	 * we grabbed the inode.
+	 *
+	 * If we can't get the reference, then we know the inode had its VFS
+	 * state torn down and hasn't yet entered the reclaim machinery.  Since
+	 * we also know that dquots are detached from an inode before it enters
+	 * reclaim, we can skip the inode.
+	 */
+	ret = igrab(VFS_I(ip)) != NULL;
+
+out_unlock:
+	spin_unlock(&ip->i_flags_lock);
+	return ret;
+}
+
 /* Drop this inode's dquots. */
 static int
 xfs_dqrele_inode(
@@ -821,6 +859,8 @@ xfs_dqrele_all_inodes(
 	return xfs_icwalk(mp, XFS_INODE_WALK_INEW_WAIT, xfs_dqrele_inode,
 			&eofb, XFS_ICWALK_DQRELE);
 }
+#else
+# define xfs_dqrele_igrab(ip)		(false)
 #endif /* CONFIG_XFS_QUOTA */
 
 /*
@@ -1493,12 +1533,12 @@ xfs_blockgc_start(
 }
 
 /*
- * Decide if the given @ip is eligible to be a part of the inode walk, and
- * grab it if so.  Returns true if it's ready to go or false if we should just
- * ignore it.
+ * Decide if the given @ip is eligible for garbage collection of speculative
+ * preallocations, and grab it if so.  Returns true if it's ready to go or
+ * false if we should just ignore it.
  */
 static bool
-xfs_inode_walk_ag_grab(
+xfs_blockgc_igrab(
 	struct xfs_inode	*ip,
 	int			flags)
 {
@@ -1657,6 +1697,27 @@ xfs_blockgc_free_quota(
 
 /* XFS Inode Cache Walking Code */
 
+/*
+ * Decide if we want to grab this inode in anticipation of doing work towards
+ * the goal.  If selected, the VFS must hold a reference to this inode, which
+ * will be released after processing.
+ */
+static inline bool
+xfs_icwalk_igrab(
+	enum xfs_icwalk_goal	goal,
+	struct xfs_inode	*ip,
+	int			iter_flags)
+{
+	switch (goal) {
+	case XFS_ICWALK_DQRELE:
+		return xfs_dqrele_igrab(ip);
+	case XFS_ICWALK_BLOCKGC:
+		return xfs_blockgc_igrab(ip, iter_flags);
+	default:
+		return false;
+	}
+}
+
 /*
  * For a given per-AG structure @pag, grab, @execute, and rele all incore
  * inodes with the given radix tree @tag.
@@ -1711,7 +1772,7 @@ xfs_icwalk_ag(
 		for (i = 0; i < nr_found; i++) {
 			struct xfs_inode *ip = batch[i];
 
-			if (done || !xfs_inode_walk_ag_grab(ip, iter_flags))
+			if (done || !xfs_icwalk_igrab(goal, ip, iter_flags))
 				batch[i] = NULL;
 
 			/*


  parent reply	other threads:[~2021-06-02 22:25 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-02 22:24 [PATCHSET v6 00/15] xfs: clean up incore inode walk functions Darrick J. Wong
2021-06-02 22:25 ` [PATCH 01/15] xfs: move the quotaoff dqrele inode walk into xfs_icache.c Darrick J. Wong
2021-06-02 22:25 ` [PATCH 02/15] xfs: detach inode dquots at the end of inactivation Darrick J. Wong
2021-06-02 22:25 ` [PATCH 03/15] xfs: move the inode walk functions further down Darrick J. Wong
2021-06-02 22:25 ` [PATCH 04/15] xfs: rename xfs_inode_walk functions to xfs_icwalk Darrick J. Wong
2021-06-03  1:02   ` Dave Chinner
2021-06-02 22:25 ` [PATCH 05/15] xfs: pass the goal of the incore inode walk to xfs_inode_walk() Darrick J. Wong
2021-06-03  1:04   ` Dave Chinner
2021-06-02 22:25 ` Darrick J. Wong [this message]
2021-06-03  1:08   ` [PATCH 06/15] xfs: separate the dqrele_all inode grab logic from xfs_inode_walk_ag_grab Dave Chinner
2021-06-02 22:25 ` [PATCH 07/15] xfs: move xfs_inew_wait call into xfs_dqrele_inode Darrick J. Wong
2021-06-02 22:25 ` [PATCH 08/15] xfs: remove iter_flags parameter from xfs_inode_walk_* Darrick J. Wong
2021-06-03  1:09   ` Dave Chinner
2021-06-03  1:38     ` Darrick J. Wong
2021-06-02 22:25 ` [PATCH 09/15] xfs: remove indirect calls from xfs_inode_walk{,_ag} Darrick J. Wong
2021-06-03  1:12   ` Dave Chinner
2021-06-02 22:25 ` [PATCH 10/15] xfs: clean up inode state flag tests in xfs_blockgc_igrab Darrick J. Wong
2021-06-03  1:13   ` Dave Chinner
2021-06-02 22:25 ` [PATCH 11/15] xfs: make the icwalk processing functions clean up the grab state Darrick J. Wong
2021-06-03  1:14   ` Dave Chinner
2021-06-02 22:26 ` [PATCH 12/15] xfs: fix radix tree tag signs Darrick J. Wong
2021-06-02 22:26 ` [PATCH 13/15] xfs: pass struct xfs_eofblocks to the inode scan callback Darrick J. Wong
2021-06-02 22:26 ` [PATCH 14/15] xfs: merge xfs_reclaim_inodes_ag into xfs_inode_walk_ag Darrick J. Wong
2021-06-02 22:26 ` [PATCH 15/15] xfs: refactor per-AG inode tagging functions Darrick J. Wong
2021-06-03  1:16   ` Dave Chinner
2021-06-03  1:27     ` Darrick J. Wong

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