Commit e3a9ac4e authored by Boris Burkov's avatar Boris Burkov Committed by Andrew Morton
Browse files

mm: add vmstat for kernel_file pages 

Kernel file pages are tricky to track because they are indistinguishable
from files whose usage is accounted to the root cgroup.

To maintain good accounting, introduce a vmstat counter tracking kernel
file pages.

Confirmed that these work as expected at a high level by mounting a btrfs
using AS_KERNEL_FILE for metadata pages, and seeing the counter rise with
fs usage then go back to a minimal level after drop_caches and finally
down to 0 after unmounting the fs.

Link: https://lkml.kernel.org/r/08ff633e3a005ed5f7691bfd9f58a5df8e474339.1755812945.git.boris@bur.io


Signed-off-by: default avatarBoris Burkov <boris@bur.io>
Suggested-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Tested-by: default avatar <syzbot@syzkaller.appspotmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qu Wenruo <wqu@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent cf1dec76

include/linux/mmzone.h

+1 −0
Original line number Diff line number Diff line
@@ -259,6 +259,7 @@ enum node_stat_item { 
	NR_HUGETLB,

#endif

	NR_BALLOON_PAGES,

	NR_KERNEL_FILE_PAGES,

	NR_VM_NODE_STAT_ITEMS

};

mm/filemap.c

+7 −0
Original line number Diff line number Diff line
@@ -190,6 +190,9 @@ static void filemap_unaccount_folio(struct address_space *mapping, 
		__lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);

		filemap_nr_thps_dec(mapping);

	}

	if (test_bit(AS_KERNEL_FILE, &folio->mapping->flags))

		mod_node_page_state(folio_pgdat(folio),

				    NR_KERNEL_FILE_PAGES, -nr);



	/*

	 * At this point folio must be either written or cleaned by
@@ -989,6 +992,10 @@ int filemap_add_folio(struct address_space *mapping, struct folio *folio, 
		if (!(gfp & __GFP_WRITE) && shadow)

			workingset_refault(folio, shadow);

		folio_add_lru(folio);

		if (kernel_file)

			mod_node_page_state(folio_pgdat(folio),

					    NR_KERNEL_FILE_PAGES,

					    folio_nr_pages(folio));

	}

	return ret;

}

mm/vmstat.c

+1 −0
Original line number Diff line number Diff line
@@ -1290,6 +1290,7 @@ const char * const vmstat_text[] = { 
	[I(NR_HUGETLB)]				= "nr_hugetlb",

#endif

	[I(NR_BALLOON_PAGES)]			= "nr_balloon_pages",

	[I(NR_KERNEL_FILE_PAGES)]		= "nr_kernel_file_pages",

#undef I



	/* system-wide enum vm_stat_item counters */