[PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence reclaim lockdep false positives

[Michal Hocko]

Updated patch after Mike noticed a BUG_ON when KM_NOLOCKDEP is used.
---
>From 1497e713e11639157aef21cae29052cb3dc7ab44 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko at suse.com>
Date: Thu, 15 Dec 2016 13:06:43 +0100
Subject: [PATCH] xfs: introduce and use KM_NOLOCKDEP to silence reclaim
 lockdep false positives

Now that the page allocator offers __GFP_NOLOCKDEP let's introduce
KM_NOLOCKDEP alias for the xfs allocation APIs. While we are at it
also change KM_NOFS users introduced by b17cb364dbbb ("xfs: fix missing
KM_NOFS tags to keep lockdep happy") and use the new flag for them
instead. There is really no reason to make these allocations contexts
weaker just because of the lockdep which even might not be enabled
in most cases.

Changes since v1
- check for KM_NOLOCKDEP in kmem_flags_convert to not hit sanity BUG_ON
  as per Mike Galbraith

Signed-off-by: Michal Hocko <mhocko at suse.com>
---
 fs/xfs/kmem.h                | 6 +++++-
 fs/xfs/libxfs/xfs_da_btree.c | 4 ++--
 fs/xfs/xfs_buf.c             | 2 +-
 fs/xfs/xfs_dir2_readdir.c    | 2 +-
 4 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h
index 689f746224e7..d5d634ef1f7f 100644
--- a/fs/xfs/kmem.h
+++ b/fs/xfs/kmem.h
@@ -33,6 +33,7 @@ typedef unsigned __bitwise xfs_km_flags_t;
 #define KM_NOFS		((__force xfs_km_flags_t)0x0004u)
 #define KM_MAYFAIL	((__force xfs_km_flags_t)0x0008u)
 #define KM_ZERO		((__force xfs_km_flags_t)0x0010u)
+#define KM_NOLOCKDEP	((__force xfs_km_flags_t)0x0020u)
 
 /*
  * We use a special process flag to avoid recursive callbacks into
@@ -44,7 +45,7 @@ kmem_flags_convert(xfs_km_flags_t flags)
 {
 	gfp_t	lflags;
 
-	BUG_ON(flags & ~(KM_SLEEP|KM_NOSLEEP|KM_NOFS|KM_MAYFAIL|KM_ZERO));
+	BUG_ON(flags & ~(KM_SLEEP|KM_NOSLEEP|KM_NOFS|KM_MAYFAIL|KM_ZERO|KM_NOLOCKDEP));
 
 	if (flags & KM_NOSLEEP) {
 		lflags = GFP_ATOMIC | __GFP_NOWARN;
@@ -57,6 +58,9 @@ kmem_flags_convert(xfs_km_flags_t flags)
 	if (flags & KM_ZERO)
 		lflags |= __GFP_ZERO;
 
+	if (flags & KM_NOLOCKDEP)
+		lflags |= __GFP_NOLOCKDEP;
+
 	return lflags;
 }
 
diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index f2dc1a950c85..b8b5f6914863 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -2429,7 +2429,7 @@ xfs_buf_map_from_irec(
 
 	if (nirecs > 1) {
 		map = kmem_zalloc(nirecs * sizeof(struct xfs_buf_map),
-				  KM_SLEEP | KM_NOFS);
+				  KM_SLEEP | KM_NOLOCKDEP);
 		if (!map)
 			return -ENOMEM;
 		*mapp = map;
@@ -2488,7 +2488,7 @@ xfs_dabuf_map(
 		 */
 		if (nfsb != 1)
 			irecs = kmem_zalloc(sizeof(irec) * nfsb,
-					    KM_SLEEP | KM_NOFS);
+					    KM_SLEEP | KM_NOLOCKDEP);
 
 		nirecs = nfsb;
 		error = xfs_bmapi_read(dp, (xfs_fileoff_t)bno, nfsb, irecs,
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 7f0a01f7b592..f31ae592dcae 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1785,7 +1785,7 @@ xfs_alloc_buftarg(
 {
 	xfs_buftarg_t		*btp;
 
-	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);
+	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOLOCKDEP);
 
 	btp->bt_mount = mp;
 	btp->bt_dev =  bdev->bd_dev;
diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
index 003a99b83bd8..033ed65d7ce6 100644
--- a/fs/xfs/xfs_dir2_readdir.c
+++ b/fs/xfs/xfs_dir2_readdir.c
@@ -503,7 +503,7 @@ xfs_dir2_leaf_getdents(
 	length = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
 	map_info = kmem_zalloc(offsetof(struct xfs_dir2_leaf_map_info, map) +
 				(length * sizeof(struct xfs_bmbt_irec)),
-			       KM_SLEEP | KM_NOFS);
+			       KM_SLEEP | KM_NOLOCKDEP);
 	map_info->map_size = length;
 
 	/*
-- 
2.10.2

-- 
Michal Hocko
SUSE Labs