Re: [PATCH 1/3] xfs: remove tag parameter from xfs_inode_walk{,_ag}

[Christoph Hellwig <hch@infradead.org>]

On Fri, Mar 19, 2021 at 06:25:01AM +0000, Christoph Hellwig wrote:
> On Thu, Mar 18, 2021 at 03:33:45PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > It turns out that there is a 1:1 mapping between the execute and tag
> > parameters that are passed to xfs_inode_walk_ag:
> > 
> > 	xfs_dqrele_inode => XFS_ICI_NO_TAG
> > 	xfs_blockgc_scan_inode => XFS_ICI_BLOCKGC_TAG
> > 
> > The radix tree tags are an implementation detail of the inode cache,
> > which means that callers outside of xfs_icache.c have no business
> > passing in radix tree tags.  Since we're about to get rid of the
> > indirect calls in the BLOCKGC case, eliminate the extra argument in
> > favor of computing the ICI tag from the execute argument passed into the
> > function.
> 
> This seems backwards to me.  I'd rather deduce the function from the
> talk, which seems like a more sensible pattern.
> 
> That being said, the quota inode walk is a little different in that it
> doesn't use any tags, so switching it to a plain list_for_each_entry_safe
> on sb->s_inodes would seems more sensible, something like this untested
> patch:

Something like this is probably going to work better (maybe split into
two patches).  I'm going to kick off some testing on it:

---
From 9ae07b6bf8c6b1337a627c8f0ad619c56511b343 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Fri, 19 Mar 2021 07:16:31 +0100
Subject: xfs: use s_inodes in xfs_qm_dqrele_all_inodes

Using xfs_inode_walk in xfs_qm_dqrele_all_inodes is complete overkill,
given that function simplify wants to iterate all live inodes known
to the VFS.  Just iterate over the s_inodes list.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_qm_syscalls.c | 50 +++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/fs/xfs/xfs_qm_syscalls.c b/fs/xfs/xfs_qm_syscalls.c
index 11f1e2fbf22f44..4e33919ed04b56 100644
--- a/fs/xfs/xfs_qm_syscalls.c
+++ b/fs/xfs/xfs_qm_syscalls.c
@@ -748,41 +748,27 @@ xfs_qm_scall_getquota_next(
 	return error;
 }
 
-STATIC int
+static void
 xfs_dqrele_inode(
 	struct xfs_inode	*ip,
-	void			*args)
+	uint			flags)
 {
-	uint			*flags = args;
-
-	/* skip quota inodes */
-	if (ip == ip->i_mount->m_quotainfo->qi_uquotaip ||
-	    ip == ip->i_mount->m_quotainfo->qi_gquotaip ||
-	    ip == ip->i_mount->m_quotainfo->qi_pquotaip) {
-		ASSERT(ip->i_udquot == NULL);
-		ASSERT(ip->i_gdquot == NULL);
-		ASSERT(ip->i_pdquot == NULL);
-		return 0;
-	}
-
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	if ((*flags & XFS_UQUOTA_ACCT) && ip->i_udquot) {
+	if ((flags & XFS_UQUOTA_ACCT) && ip->i_udquot) {
 		xfs_qm_dqrele(ip->i_udquot);
 		ip->i_udquot = NULL;
 	}
-	if ((*flags & XFS_GQUOTA_ACCT) && ip->i_gdquot) {
+	if ((flags & XFS_GQUOTA_ACCT) && ip->i_gdquot) {
 		xfs_qm_dqrele(ip->i_gdquot);
 		ip->i_gdquot = NULL;
 	}
-	if ((*flags & XFS_PQUOTA_ACCT) && ip->i_pdquot) {
+	if ((flags & XFS_PQUOTA_ACCT) && ip->i_pdquot) {
 		xfs_qm_dqrele(ip->i_pdquot);
 		ip->i_pdquot = NULL;
 	}
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	return 0;
 }
 
-
 /*
  * Go thru all the inodes in the file system, releasing their dquots.
  *
@@ -794,7 +780,29 @@ xfs_qm_dqrele_all_inodes(
 	struct xfs_mount	*mp,
 	uint			flags)
 {
+	struct super_block	*sb = mp->m_super;
+	struct inode		*inode, *old_inode = NULL;
+
 	ASSERT(mp->m_quotainfo);
-	xfs_inode_walk(mp, XFS_INODE_WALK_INEW_WAIT, xfs_dqrele_inode,
-			&flags, XFS_ICI_NO_TAG);
+
+	spin_lock(&sb->s_inode_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		struct xfs_inode	*ip = XFS_I(inode);
+
+		if (xfs_is_quota_inode(&mp->m_sb, ip->i_ino))
+			continue;
+		if (!igrab(inode))
+			continue;
+		spin_unlock(&sb->s_inode_list_lock);
+
+		iput(old_inode);
+		old_inode = inode;
+
+		xfs_dqrele_inode(ip, flags);
+
+		spin_lock(&sb->s_inode_list_lock);
+	}
+	spin_unlock(&sb->s_inode_list_lock);
+
+	iput(old_inode);
 }
-- 
2.30.1