truncate,shmem: Handle truncates that split large folios
Handle folio splitting in the parts of the truncation functions which
already handle partial pages. Factor all that code out into a new
function called truncate_inode_partial_folio().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
diff --git a/mm/shmem.c b/mm/shmem.c
index bbfa2d0..e4c9e5c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -880,30 +880,26 @@ void shmem_unlock_mapping(struct address_space *mapping)
}
}
-/*
- * Check whether a hole-punch or truncation needs to split a huge page,
- * returning true if no split was required, or the split has been successful.
- *
- * Eviction (or truncation to 0 size) should never need to split a huge page;
- * but in rare cases might do so, if shmem_undo_range() failed to trylock on
- * head, and then succeeded to trylock on tail.
- *
- * A split can only succeed when there are no additional references on the
- * huge page: so the split below relies upon find_get_entries() having stopped
- * when it found a subpage of the huge page, without getting further references.
- */
-static bool shmem_punch_compound(struct page *page, pgoff_t start, pgoff_t end)
+static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
{
- if (!PageTransCompound(page))
- return true;
+ struct folio *folio;
+ struct page *page;
- /* Just proceed to delete a huge page wholly within the range punched */
- if (PageHead(page) &&
- page->index >= start && page->index + HPAGE_PMD_NR <= end)
- return true;
-
- /* Try to split huge page, so we can truly punch the hole or truncate */
- return split_huge_page(page) >= 0;
+ /*
+ * At first avoid shmem_getpage(,,,SGP_READ): that fails
+ * beyond i_size, and reports fallocated pages as holes.
+ */
+ folio = __filemap_get_folio(inode->i_mapping, index,
+ FGP_ENTRY | FGP_LOCK, 0);
+ if (!xa_is_value(folio))
+ return folio;
+ /*
+ * But read a page back from swap if any of it is within i_size
+ * (although in some cases this is just a waste of time).
+ */
+ page = NULL;
+ shmem_getpage(inode, index, &page, SGP_READ);
+ return page ? page_folio(page) : NULL;
}
/*
@@ -917,10 +913,10 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
struct shmem_inode_info *info = SHMEM_I(inode);
pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
pgoff_t end = (lend + 1) >> PAGE_SHIFT;
- unsigned int partial_start = lstart & (PAGE_SIZE - 1);
- unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
struct folio_batch fbatch;
pgoff_t indices[PAGEVEC_SIZE];
+ struct folio *folio;
+ bool same_folio;
long nr_swaps_freed = 0;
pgoff_t index;
int i;
@@ -936,7 +932,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
while (index < end && find_lock_entries(mapping, index, end - 1,
&fbatch, indices)) {
for (i = 0; i < folio_batch_count(&fbatch); i++) {
- struct folio *folio = fbatch.folios[i];
+ folio = fbatch.folios[i];
index = indices[i];
@@ -959,33 +955,30 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
index++;
}
- if (partial_start) {
- struct page *page = NULL;
- shmem_getpage(inode, start - 1, &page, SGP_READ);
- if (page) {
- unsigned int top = PAGE_SIZE;
- if (start > end) {
- top = partial_end;
- partial_end = 0;
- }
- zero_user_segment(page, partial_start, top);
- set_page_dirty(page);
- unlock_page(page);
- put_page(page);
+ same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
+ folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
+ if (folio) {
+ same_folio = lend < folio_pos(folio) + folio_size(folio);
+ folio_mark_dirty(folio);
+ if (!truncate_inode_partial_folio(folio, lstart, lend)) {
+ start = folio->index + folio_nr_pages(folio);
+ if (same_folio)
+ end = folio->index;
}
+ folio_unlock(folio);
+ folio_put(folio);
+ folio = NULL;
}
- if (partial_end) {
- struct page *page = NULL;
- shmem_getpage(inode, end, &page, SGP_READ);
- if (page) {
- zero_user_segment(page, 0, partial_end);
- set_page_dirty(page);
- unlock_page(page);
- put_page(page);
- }
+
+ if (!same_folio)
+ folio = shmem_get_partial_folio(inode, lend >> PAGE_SHIFT);
+ if (folio) {
+ folio_mark_dirty(folio);
+ if (!truncate_inode_partial_folio(folio, lstart, lend))
+ end = folio->index;
+ folio_unlock(folio);
+ folio_put(folio);
}
- if (start >= end)
- return;
index = start;
while (index < end) {
@@ -1001,7 +994,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
continue;
}
for (i = 0; i < folio_batch_count(&fbatch); i++) {
- struct folio *folio = fbatch.folios[i];
+ folio = fbatch.folios[i];
index = indices[i];
if (xa_is_value(folio)) {
@@ -1019,8 +1012,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
folio_lock(folio);
if (!unfalloc || !folio_test_uptodate(folio)) {
- struct page *page = folio_file_page(folio,
- index);
if (folio_mapping(folio) != mapping) {
/* Page was replaced by swap: retry */
folio_unlock(folio);
@@ -1029,18 +1020,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
}
VM_BUG_ON_FOLIO(folio_test_writeback(folio),
folio);
- if (shmem_punch_compound(page, start, end))
- truncate_inode_folio(mapping, folio);
- else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
- /* Wipe the page and don't get stuck */
- clear_highpage(page);
- flush_dcache_page(page);
- folio_mark_dirty(folio);
- if (index <
- round_up(start, HPAGE_PMD_NR))
- start = index + 1;
- }
+ truncate_inode_folio(mapping, folio);
}
+ index = folio->index + folio_nr_pages(folio) - 1;
folio_unlock(folio);
}
folio_batch_remove_exceptionals(&fbatch);
