From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: dax: account DAX entries as nrpages Simplify mapping_needs_writeback() by accounting DAX entries as pages instead of exceptional entries. Link: https://lkml.kernel.org/r/20201026151849.24232-4-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Tested-by: Vishal Verma <vishal.l.verma@xxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/dax.c | 6 +++--- mm/filemap.c | 3 --- 2 files changed, 3 insertions(+), 6 deletions(-) --- a/fs/dax.c~dax-account-dax-entries-as-nrpages +++ a/fs/dax.c @@ -525,7 +525,7 @@ retry: dax_disassociate_entry(entry, mapping, false); xas_store(xas, NULL); /* undo the PMD join */ dax_wake_entry(xas, entry, true); - mapping->nrexceptional--; + mapping->nrpages -= PG_PMD_NR; entry = NULL; xas_set(xas, index); } @@ -541,7 +541,7 @@ retry: dax_lock_entry(xas, entry); if (xas_error(xas)) goto out_unlock; - mapping->nrexceptional++; + mapping->nrpages += 1UL << order; } out_unlock: @@ -661,7 +661,7 @@ static int __dax_invalidate_entry(struct goto out; dax_disassociate_entry(entry, mapping, trunc); xas_store(&xas, NULL); - mapping->nrexceptional--; + mapping->nrpages -= 1UL << dax_entry_order(entry); ret = 1; out: put_unlocked_entry(&xas, entry); --- a/mm/filemap.c~dax-account-dax-entries-as-nrpages +++ a/mm/filemap.c @@ -618,9 +618,6 @@ EXPORT_SYMBOL(filemap_fdatawait_keep_err /* Returns true if writeback might be needed or already in progress. */ static bool mapping_needs_writeback(struct address_space *mapping) { - if (dax_mapping(mapping)) - return mapping->nrexceptional; - return mapping->nrpages; } _
