The patch titled
Subject: mm: warn on deleting redirtied only if accounted
has been added to the -mm tree. Its filename is
mm-warn-on-deleting-redirtied-only-if-accounted.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-warn-on-deleting-redirtied-only-if-accounted.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-warn-on-deleting-redirtied-only-if-accounted.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: warn on deleting redirtied only if accounted
filemap_unaccount_folio() has a WARN_ON_ONCE(folio_test_dirty(folio)). It
is good to warn of late dirtying on a persistent filesystem, but late
dirtying on tmpfs can only lose data which is expected to be thrown away;
and it's a pity if that warning comes ONCE on tmpfs, then hides others
which really matter. Make it conditional on mapping_cap_writeback().
Cleanup: then folio_account_cleaned() no longer needs to check that for
itself, and so no longer needs to know the mapping.
Link: https://lkml.kernel.org/r/b5a1106c-7226-a5c6-ad41-ad4832cae1f@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 3 +--
mm/filemap.c | 14 +++++++++-----
mm/page-writeback.c | 18 ++++++++----------
3 files changed, 18 insertions(+), 17 deletions(-)
--- a/include/linux/pagemap.h~mm-warn-on-deleting-redirtied-only-if-accounted
+++ a/include/linux/pagemap.h
@@ -991,8 +991,7 @@ static inline void __set_page_dirty(stru
{
__folio_mark_dirty(page_folio(page), mapping, warn);
}
-void folio_account_cleaned(struct folio *folio, struct address_space *mapping,
- struct bdi_writeback *wb);
+void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb);
void __folio_cancel_dirty(struct folio *folio);
static inline void folio_cancel_dirty(struct folio *folio)
{
--- a/mm/filemap.c~mm-warn-on-deleting-redirtied-only-if-accounted
+++ a/mm/filemap.c
@@ -193,16 +193,20 @@ static void filemap_unaccount_folio(stru
/*
* At this point folio must be either written or cleaned by
* truncate. Dirty folio here signals a bug and loss of
- * unwritten data.
+ * unwritten data - on ordinary filesystems.
*
- * This fixes dirty accounting after removing the folio entirely
+ * But it's harmless on in-memory filesystems like tmpfs; and can
+ * occur when a driver which did get_user_pages() sets page dirty
+ * before putting it, while the inode is being finally evicted.
+ *
+ * Below fixes dirty accounting after removing the folio entirely
* but leaves the dirty flag set: it has no effect for truncated
* folio and anyway will be cleared before returning folio to
* buddy allocator.
*/
- if (WARN_ON_ONCE(folio_test_dirty(folio)))
- folio_account_cleaned(folio, mapping,
- inode_to_wb(mapping->host));
+ if (WARN_ON_ONCE(folio_test_dirty(folio) &&
+ mapping_can_writeback(mapping)))
+ folio_account_cleaned(folio, inode_to_wb(mapping->host));
}
/*
--- a/mm/page-writeback.c~mm-warn-on-deleting-redirtied-only-if-accounted
+++ a/mm/page-writeback.c
@@ -2548,16 +2548,14 @@ static void folio_account_dirtied(struct
*
* Caller must hold lock_page_memcg().
*/
-void folio_account_cleaned(struct folio *folio, struct address_space *mapping,
- struct bdi_writeback *wb)
+void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb)
{
- if (mapping_can_writeback(mapping)) {
- long nr = folio_nr_pages(folio);
- lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr);
- zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
- wb_stat_mod(wb, WB_RECLAIMABLE, -nr);
- task_io_account_cancelled_write(nr * PAGE_SIZE);
- }
+ long nr = folio_nr_pages(folio);
+
+ lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr);
+ zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
+ wb_stat_mod(wb, WB_RECLAIMABLE, -nr);
+ task_io_account_cancelled_write(nr * PAGE_SIZE);
}
/*
@@ -2768,7 +2766,7 @@ void __folio_cancel_dirty(struct folio *
wb = unlocked_inode_to_wb_begin(inode, &cookie);
if (folio_test_clear_dirty(folio))
- folio_account_cleaned(folio, mapping, wb);
+ folio_account_cleaned(folio, wb);
unlocked_inode_to_wb_end(inode, &cookie);
folio_memcg_unlock(folio);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-fs-delete-pf_swapwrite.patch
tmpfs-support-for-file-creation-time-fix.patch
shmem-mapping_set_exiting-to-help-mapped-resilience.patch
mm-_install_special_mapping-apply-vm_locked_clear_mask.patch
mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch
mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch
mm-delete-__clearpagewaiters.patch
mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch
mm-warn-on-deleting-redirtied-only-if-accounted.patch
