FROMGIT: swap: remove remnants of polling from read_swap_cache_async

Patch series "Per-VMA lock support for swap and userfaults", v7.

When per-VMA locks were introduced in [1] several types of page faults
would still fall back to mmap_lock to keep the patchset simple.  Among
them are swap and userfault pages.  The main reason for skipping those
cases was the fact that mmap_lock could be dropped while handling these
faults and that required additional logic to be implemented.  Implement
the mechanism to allow per-VMA locks to be dropped for these cases.

First, change handle_mm_fault to drop per-VMA locks when returning
VM_FAULT_RETRY or VM_FAULT_COMPLETED to be consistent with the way
mmap_lock is handled.  Then change folio_lock_or_retry to accept vm_fault
and return vm_fault_t which simplifies later patches.  Finally allow swap
and uffd page faults to be handled under per-VMA locks by dropping per-VMA
and retrying, the same way it's done under mmap_lock.  Naturally, once VMA
lock is dropped that VMA should be assumed unstable and can't be used.

This patch (of 6):

Commit [1] introduced IO polling support duding swapin to reduce swap read
latency for block devices that can be polled.  However later commit [2]
removed polling support.  Therefore it seems safe to remove do_poll
parameter in read_swap_cache_async and always call swap_readpage with
synchronous=false waiting for IO completion in folio_lock_or_retry.

[1] commit 2395562 ("swap: add block io poll in swapin path")
[2] commit 9650b45 ("block: ignore RWF_HIPRI hint for sync dio")

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Suggested-by: "Huang, Ying" <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Howells <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Punit Agrawal <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

(cherry picked from commit 4296c6a817b421061d6e0b9c654c7d4d5a038a5b
https: //git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
Bug: 161210518
Change-Id: I3d647ba4d6093f4e3db2c4ff759e5ce59b45b0e1
Signed-off-by: Suren Baghdasaryan <[email protected]>

mm/madvise.c

@@ -223,7 +223,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 		trace_android_vh_madvise_swapin_walk_pmd_entry(entry);
 
 		page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
-					     vma, index, false, &splug);
+					     vma, index, &splug);
 		if (page)
 			put_page(page);
 	}
@@ -259,7 +259,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 		rcu_read_unlock();
 
 		page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
-					     NULL, 0, false, &splug);
+					     NULL, 0, &splug);
 		if (page)
 			put_page(page);
 

mm/swap.h

@@ -46,7 +46,6 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index);
 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 				   struct vm_area_struct *vma,
 				   unsigned long addr,
-				   bool do_poll,
 				   struct swap_iocb **plug);
 struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 				     struct vm_area_struct *vma,

mm/swap_state.c

@@ -515,15 +515,14 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
  */
 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 				   struct vm_area_struct *vma,
-				   unsigned long addr, bool do_poll,
-				   struct swap_iocb **plug)
+				   unsigned long addr, struct swap_iocb **plug)
 {
 	bool page_was_allocated;
 	struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
 			vma, addr, &page_was_allocated);
 
 	if (page_was_allocated)
-		swap_readpage(retpage, do_poll, plug);
+		swap_readpage(retpage, false, plug);
 
 	return retpage;
 }
@@ -618,15 +617,14 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	struct swap_info_struct *si = swp_swap_info(entry);
 	struct blk_plug plug;
 	struct swap_iocb *splug = NULL;
-	bool do_poll = true, page_allocated;
+	bool page_allocated;
 	struct vm_area_struct *vma = vmf->vma;
 	unsigned long addr = vmf->address;
 
 	mask = swapin_nr_pages(offset) - 1;
 	if (!mask)
 		goto skip;
 
-	do_poll = false;
 	/* Read a page_cluster sized and aligned cluster around offset. */
 	start_offset = offset & ~mask;
 	end_offset = offset | mask;
@@ -658,7 +656,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	lru_add_drain();	/* Push any new pages onto the LRU now */
 skip:
 	/* The page was likely read above, so no need for plugging here */
-	return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll, NULL);
+	return read_swap_cache_async(entry, gfp_mask, vma, addr, NULL);
 }
 
 int init_swap_address_space(unsigned int type, unsigned long nr_pages)
@@ -832,7 +830,7 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
 skip:
 	/* The page was likely read above, so no need for plugging here */
 	return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
-				     ra_info.win == 1, NULL);
+				     NULL);
 }
 
 /**