Commit b0802b22 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

shmem: convert shmem_fallocate() to use a folio 

Call shmem_get_folio() and use the folio APIs instead of the page APIs. 
Saves several calls to compound_head() and removes assumptions about the
size of a large folio.

Link: https://lkml.kernel.org/r/20220902194653.1739778-29-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4601e2fc

mm/shmem.c

+17 −19
Original line number Diff line number Diff line
@@ -2787,7 +2787,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, 
		info->fallocend = end;



	for (index = start; index < end; ) {

		struct page *page;

		struct folio *folio;



		/*

		 * Good, the fallocate(2) manpage permits EINTR: we may have
@@ -2798,10 +2798,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, 
		else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)

			error = -ENOMEM;

		else

			error = shmem_getpage(inode, index, &page, SGP_FALLOC);

			error = shmem_get_folio(inode, index, &folio,

						SGP_FALLOC);

		if (error) {

			info->fallocend = undo_fallocend;

			/* Remove the !PageUptodate pages we added */

			/* Remove the !uptodate folios we added */

			if (index > start) {

				shmem_undo_range(inode,

				    (loff_t)start << PAGE_SHIFT,
@@ -2810,37 +2811,34 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, 
			goto undone;

		}



		index++;

		/*

		 * Here is a more important optimization than it appears:

		 * a second SGP_FALLOC on the same huge page will clear it,

		 * making it PageUptodate and un-undoable if we fail later.

		 * a second SGP_FALLOC on the same large folio will clear it,

		 * making it uptodate and un-undoable if we fail later.

		 */

		if (PageTransCompound(page)) {

			index = round_up(index, HPAGE_PMD_NR);

		index = folio_next_index(folio);

		/* Beware 32-bit wraparound */

		if (!index)

			index--;

		}



		/*

		 * Inform shmem_writepage() how far we have reached.

		 * No need for lock or barrier: we have the page lock.

		 */

		if (!PageUptodate(page))

		if (!folio_test_uptodate(folio))

			shmem_falloc.nr_falloced += index - shmem_falloc.next;

		shmem_falloc.next = index;



		/*

		 * If !PageUptodate, leave it that way so that freeable pages

		 * If !uptodate, leave it that way so that freeable folios

		 * can be recognized if we need to rollback on error later.

		 * But set_page_dirty so that memory pressure will swap rather

		 * than free the pages we are allocating (and SGP_CACHE pages

		 * But mark it dirty so that memory pressure will swap rather

		 * than free the folios we are allocating (and SGP_CACHE folios

		 * might still be clean: we now need to mark those dirty too).

		 */

		set_page_dirty(page);

		unlock_page(page);

		put_page(page);

		folio_mark_dirty(folio);

		folio_unlock(folio);

		folio_put(folio);

		cond_resched();

	}