[PATCH v4 68/68] 9p, afs, ceph, cifs, nfs: Use current_is_kswapd() rather than gfpflags_allow_blocking()

[David Howells]

In 9p, afs ceph, cifs and nfs, gfpflags_allow_blocking() (which wraps a
test for __GFP_DIRECT_RECLAIM being set) is used to determine if
->releasepage() should wait for the completion of a DIO write to fscache
with something like:

	if (folio_test_fscache(folio)) {
		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
			return false;
		folio_wait_fscache(folio);
	}

Instead, current_is_kswapd() should be used instead.

Note that this is based on a patch originally by Zhaoyang Huang[1].  In
addition to extending it to the other network filesystems and putting it on
top of my fscache rewrite, it also needs to include linux/swap.h in a bunch
of places.  Can current_is_kswapd() be moved to linux/mm.h?

Originally-signed-off-by: Zhaoyang Huang <zhaoyang.huang at unisoc.com>
Co-developed-by: David Howells <dhowells at redhat.com>
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Zhaoyang Huang <zhaoyang.huang at unisoc.com>
cc: Dominique Martinet <asmadeus at codewreck.org>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: Jeff Layton <jlayton at kernel.org>
cc: Steve French <sfrench at samba.org>
cc: Trond Myklebust <trond.myklebust at hammerspace.com>
cc: linux-cachefs at redhat.com
cc: v9fs-developer at lists.sourceforge.net
cc: linux-afs at lists.infradead.org
cc: ceph-devel at vger.kernel.org
cc: linux-cifs at vger.kernel.org
cc: linux-nfs at vger.kernel.org
cc: linux-mm at kvack.org
Link: https://lore.kernel.org/r/1638952658-20285-1-git-send-email-huangzhaoyang@gmail.com/ [1]
---

 fs/9p/vfs_addr.c |    3 ++-
 fs/afs/file.c    |    3 ++-
 fs/ceph/addr.c   |    3 ++-
 fs/cifs/file.c   |    2 +-
 fs/nfs/fscache.h |    3 ++-
 5 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index f3f349f460e5..c72e9f8f5f32 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -16,6 +16,7 @@
 #include <linux/pagemap.h>
 #include <linux/idr.h>
 #include <linux/sched.h>
+#include <linux/swap.h>
 #include <linux/uio.h>
 #include <linux/netfs.h>
 #include <net/9p/9p.h>
@@ -143,7 +144,7 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)
 		return 0;
 #ifdef CONFIG_9P_FSCACHE
 	if (folio_test_fscache(folio)) {
-		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
+		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return 0;
 		folio_wait_fscache(folio);
 	}
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 572063dad0b3..5b98db127a1b 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -14,6 +14,7 @@
 #include <linux/gfp.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/mm.h>
+#include <linux/swap.h>
 #include <linux/netfs.h>
 #include "internal.h"
 
@@ -517,7 +518,7 @@ static int afs_releasepage(struct page *page, gfp_t gfp)
 	 * elected to wait */
 #ifdef CONFIG_AFS_FSCACHE
 	if (folio_test_fscache(folio)) {
-		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
+		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return false;
 		folio_wait_fscache(folio);
 	}
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index e836f8f1d4f8..b3d9459c9bbd 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -4,6 +4,7 @@
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include <linux/swap.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/pagevec.h>
@@ -174,7 +175,7 @@ static int ceph_releasepage(struct page *page, gfp_t gfp)
 		return 0;
 
 	if (PageFsCache(page)) {
-		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
+		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return 0;
 		wait_on_page_fscache(page);
 	}
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 22b66ce10115..d872f6fe8e7d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4809,7 +4809,7 @@ static int cifs_release_page(struct page *page, gfp_t gfp)
 	if (PagePrivate(page))
 		return 0;
 	if (PageFsCache(page)) {
-		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
+		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return false;
 		wait_on_page_fscache(page);
 	}
diff --git a/fs/nfs/fscache.h b/fs/nfs/fscache.h
index e0220fc40366..25a5c0f82392 100644
--- a/fs/nfs/fscache.h
+++ b/fs/nfs/fscache.h
@@ -8,6 +8,7 @@
 #ifndef _NFS_FSCACHE_H
 #define _NFS_FSCACHE_H
 
+#include <linux/swap.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_mount.h>
 #include <linux/nfs4_mount.h>
@@ -52,7 +53,7 @@ extern void __nfs_readpage_to_fscache(struct inode *, struct page *);
 static inline int nfs_fscache_release_page(struct page *page, gfp_t gfp)
 {
 	if (PageFsCache(page)) {
-		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
+		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return false;
 		wait_on_page_fscache(page);
 		fscache_note_page_release(nfs_i_fscache(page->mapping->host));