From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/fs: delete PF_SWAPWRITE
PF_SWAPWRITE has been redundant since v3.2 commit ee72886d8ed5 ("mm:
vmscan: do not writeback filesystem pages in direct reclaim").
Coincidentally, NeilBrown's current patch "remove inode_congested()"
deletes may_write_to_inode(), which appeared to be the one function which
took notice of PF_SWAPWRITE. But if you study the old logic, and the
conditions under which may_write_to_inode() was called, you discover that
flag and function have been pointless for a decade.
Link: https://lkml.kernel.org/r/75e80e7-742d-e3bd-531-614db8961e4@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 3 ---
fs/xfs/libxfs/xfs_btree.c | 2 +-
include/linux/sched.h | 1 -
mm/migrate.c | 7 -------
mm/vmscan.c | 8 ++------
5 files changed, 3 insertions(+), 18 deletions(-)
--- a/fs/fs-writeback.c~mm-fs-delete-pf_swapwrite
+++ a/fs/fs-writeback.c
@@ -2197,7 +2197,6 @@ void wb_workfn(struct work_struct *work)
long pages_written;
set_worker_desc("flush-%s", bdi_dev_name(wb->bdi));
- current->flags |= PF_SWAPWRITE;
if (likely(!current_is_workqueue_rescuer() ||
!test_bit(WB_registered, &wb->state))) {
@@ -2226,8 +2225,6 @@ void wb_workfn(struct work_struct *work)
wb_wakeup(wb);
else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
wb_wakeup_delayed(wb);
-
- current->flags &= ~PF_SWAPWRITE;
}
/*
--- a/fs/xfs/libxfs/xfs_btree.c~mm-fs-delete-pf_swapwrite
+++ a/fs/xfs/libxfs/xfs_btree.c
@@ -2818,7 +2818,7 @@ xfs_btree_split_worker(
* in any way.
*/
if (args->kswapd)
- new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ new_pflags |= PF_MEMALLOC | PF_KSWAPD;
current_set_flags_nested(&pflags, new_pflags);
xfs_trans_set_context(args->cur->bc_tp);
--- a/include/linux/sched.h~mm-fs-delete-pf_swapwrite
+++ a/include/linux/sched.h
@@ -1689,7 +1689,6 @@ extern struct pid *cad_pid;
* I am cleaning dirty pages from some other bdi. */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */
-#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
#define PF_MEMALLOC_PIN 0x10000000 /* Allocation context constrained to zones which allow long term pinning. */
--- a/mm/migrate.c~mm-fs-delete-pf_swapwrite
+++ a/mm/migrate.c
@@ -1350,7 +1350,6 @@ int migrate_pages(struct list_head *from
bool is_thp = false;
struct page *page;
struct page *page2;
- int swapwrite = current->flags & PF_SWAPWRITE;
int rc, nr_subpages;
LIST_HEAD(ret_pages);
LIST_HEAD(thp_split_pages);
@@ -1359,9 +1358,6 @@ int migrate_pages(struct list_head *from
trace_mm_migrate_pages_start(mode, reason);
- if (!swapwrite)
- current->flags |= PF_SWAPWRITE;
-
thp_subpage_migration:
for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
retry = 0;
@@ -1516,9 +1512,6 @@ out:
trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded,
nr_thp_failed, nr_thp_split, mode, reason);
- if (!swapwrite)
- current->flags &= ~PF_SWAPWRITE;
-
if (ret_succeeded)
*ret_succeeded = nr_succeeded;
--- a/mm/vmscan.c~mm-fs-delete-pf_swapwrite
+++ a/mm/vmscan.c
@@ -4457,7 +4457,7 @@ static int kswapd(void *p)
* us from recursively trying to free more memory as we're
* trying to free the first piece of memory in the first place).
*/
- tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ tsk->flags |= PF_MEMALLOC | PF_KSWAPD;
set_freezable();
WRITE_ONCE(pgdat->kswapd_order, 0);
@@ -4508,7 +4508,7 @@ kswapd_try_sleep:
goto kswapd_try_sleep;
}
- tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
+ tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD);
return 0;
}
@@ -4749,11 +4749,8 @@ static int __node_reclaim(struct pglist_
fs_reclaim_acquire(sc.gfp_mask);
/*
* We need to be able to allocate from the reserves for RECLAIM_UNMAP
- * and we also need to be able to write out pages for RECLAIM_WRITE
- * and RECLAIM_UNMAP.
*/
noreclaim_flag = memalloc_noreclaim_save();
- p->flags |= PF_SWAPWRITE;
set_task_reclaim_state(p, &sc.reclaim_state);
if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) {
@@ -4767,7 +4764,6 @@ static int __node_reclaim(struct pglist_
}
set_task_reclaim_state(p, NULL);
- current->flags &= ~PF_SWAPWRITE;
memalloc_noreclaim_restore(noreclaim_flag);
fs_reclaim_release(sc.gfp_mask);
psi_memstall_leave(&pflags);
_
