[PATCH 1/4] xfs: remove dead kswapd flag inheritance from btree split worker

[Kefeng Wang <wangkefeng.wang@huawei.com>]

Commit 1f6d64829db7 ("xfs: block allocation work needs to be kswapd
aware") added PF_MEMALLOC | PF_KSWAPD inheritance to
xfs_btree_split_worker() so that block allocation offloaded from
kswapd to a workqueue thread could access emergency memory reserves
and avoid reclaim throttling.

pageout() no longer calls ->writepage() for filesystem folios -- it
returns PAGE_ACTIVATE for non-shmem, non-anon pages.  kswapd therefore
never enters XFS writeback and cannot reach btree split.  The only
path that offloads btree splits is unwritten extent conversion at IO
completion (xfs_end_io -> xfs_iomap_write_unwritten), which runs in
a workqueue context where current_is_kswapd() is always false.

Let's remove the dead kswapd flag and related codes.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 fs/xfs/libxfs/xfs_btree.c | 18 +-----------------
 fs/xfs/xfs_platform.h     |  4 ----
 2 files changed, 1 insertion(+), 21 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 60ef7f08b1d3..6738d9d1511b 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -2994,7 +2994,6 @@ struct xfs_btree_split_args {
 	struct xfs_btree_cur	**curp;
 	int			*stat;		/* success/failure */
 	int			result;
-	bool			kswapd;	/* allocation in kswapd context */
 	struct completion	*done;
 	struct work_struct	work;
 };
@@ -3008,33 +3007,18 @@ xfs_btree_split_worker(
 {
 	struct xfs_btree_split_args	*args = container_of(work,
 						struct xfs_btree_split_args, work);
-	unsigned long		pflags;
-	unsigned long		new_pflags = 0;
-
-	/*
-	 * we are in a transaction context here, but may also be doing work
-	 * in kswapd context, and hence we may need to inherit that state
-	 * temporarily to ensure that we don't block waiting for memory reclaim
-	 * in any way.
-	 */
-	if (args->kswapd)
-		new_pflags |= PF_MEMALLOC | PF_KSWAPD;
-
-	current_set_flags_nested(&pflags, new_pflags);
 	xfs_trans_set_context(args->cur->bc_tp);
 
 	args->result = __xfs_btree_split(args->cur, args->level, args->ptrp,
 					 args->key, args->curp, args->stat);
 
 	xfs_trans_clear_context(args->cur->bc_tp);
-	current_restore_flags_nested(&pflags, new_pflags);
 
 	/*
 	 * Do not access args after complete() has run here. We don't own args
 	 * and the owner may run and free args before we return here.
 	 */
 	complete(args->done);
-
 }
 
 /*
@@ -3078,7 +3062,7 @@ xfs_btree_split(
 	args.curp = curp;
 	args.stat = stat;
 	args.done = &done;
-	args.kswapd = current_is_kswapd();
+
 	INIT_WORK_ONSTACK(&args.work, xfs_btree_split_worker);
 	queue_work(xfs_alloc_wq, &args.work);
 	wait_for_completion(&done);
diff --git a/fs/xfs/xfs_platform.h b/fs/xfs/xfs_platform.h
index 5d542e95fe44..a49fa159894d 100644
--- a/fs/xfs/xfs_platform.h
+++ b/fs/xfs/xfs_platform.h
@@ -115,10 +115,6 @@ typedef __u32			xfs_nlink_t;
 #define xfs_blockgc_secs	xfs_params.blockgc_timer.val
 
 #define current_cpu()		(raw_smp_processor_id())
-#define current_set_flags_nested(sp, f)		\
-		(*(sp) = current->flags, current->flags |= (f))
-#define current_restore_flags_nested(sp, f)	\
-		(current->flags = ((current->flags & ~(f)) | (*(sp) & (f))))
 
 #define NBBY		8		/* number of bits per byte */
 
-- 
2.55.0