mm: shmem: extend shmem_unused_huge_shrink() to all sizes

Although shmem_get_folio_gfp() is correctly putting inodes on the
shrinklist according to the folio size, shmem_unused_huge_shrink() was
still dealing with that shrinklist in terms of HPAGE_PMD_SIZE.

Generalize that; and to handle the mixture of sizes more sensibly,
shmem_alloc_and_add_folio() give it a number of pages to be freed
(approximate: no need to minimize that with an exact calculation) instead
of a number of inodes to split.

[akpm@linux-foundation.org: comment tweak, per David]
Link: https://lkml.kernel.org/r/d8c40850-6774-7a93-1e2c-8d941683b260@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index bf50ecb906ce2c0111fe15c1e1b656d4ce552975..553b99cb265e542948cf1f41b7503e89223f1566 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -636,15 +636,14 @@ static const char *shmem_format_huge(int huge)
 #endif
 
 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
-               struct shrink_control *sc, unsigned long nr_to_split)
+               struct shrink_control *sc, unsigned long nr_to_free)
 {
        LIST_HEAD(list), *pos, *next;
-       LIST_HEAD(to_remove);
        struct inode *inode;
        struct shmem_inode_info *info;
        struct folio *folio;
        unsigned long batch = sc ? sc->nr_to_scan : 128;
-       int split = 0;
+       unsigned long split = 0, freed = 0;
 
        if (list_empty(&sbinfo->shrinklist))
                return SHRINK_STOP;
@@ -662,13 +661,6 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
                        goto next;
                }
 
-               /* Check if there's anything to gain */
-               if (round_up(inode->i_size, PAGE_SIZE) ==
-                               round_up(inode->i_size, HPAGE_PMD_SIZE)) {
-                       list_move(&info->shrinklist, &to_remove);
-                       goto next;
-               }
-
                list_move(&info->shrinklist, &list);
 next:
                sbinfo->shrinklist_len--;
@@ -677,34 +669,36 @@ next:
        }
        spin_unlock(&sbinfo->shrinklist_lock);
 
-       list_for_each_safe(pos, next, &to_remove) {
-               info = list_entry(pos, struct shmem_inode_info, shrinklist);
-               inode = &info->vfs_inode;
-               list_del_init(&info->shrinklist);
-               iput(inode);
-       }
-
        list_for_each_safe(pos, next, &list) {
+               pgoff_t next, end;
+               loff_t i_size;
                int ret;
-               pgoff_t index;
 
                info = list_entry(pos, struct shmem_inode_info, shrinklist);
                inode = &info->vfs_inode;
 
-               if (nr_to_split && split >= nr_to_split)
+               if (nr_to_free && freed >= nr_to_free)
                        goto move_back;
 
-               index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
-               folio = filemap_get_folio(inode->i_mapping, index);
-               if (IS_ERR(folio))
+               i_size = i_size_read(inode);
+               folio = filemap_get_entry(inode->i_mapping, i_size / PAGE_SIZE);
+               if (!folio || xa_is_value(folio))
                        goto drop;
 
-               /* No huge page at the end of the file: nothing to split */
+               /* No large folio at the end of the file: nothing to split */
                if (!folio_test_large(folio)) {
                        folio_put(folio);
                        goto drop;
                }
 
+               /* Check if there is anything to gain from splitting */
+               next = folio_next_index(folio);
+               end = shmem_fallocend(inode, DIV_ROUND_UP(i_size, PAGE_SIZE));
+               if (end <= folio->index || end >= next) {
+                       folio_put(folio);
+                       goto drop;
+               }
+
                /*
                 * Move the inode on the list back to shrinklist if we failed
                 * to lock the page at this time.
@@ -725,6 +719,7 @@ next:
                if (ret)
                        goto move_back;
 
+               freed += next - end;
                split++;
 drop:
                list_del_init(&info->shrinklist);
@@ -769,7 +764,7 @@ static long shmem_unused_huge_count(struct super_block *sb,
 #define shmem_huge SHMEM_HUGE_DENY
 
 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
-               struct shrink_control *sc, unsigned long nr_to_split)
+               struct shrink_control *sc, unsigned long nr_to_free)
 {
        return 0;
 }
@@ -1851,7 +1846,7 @@ allocated:
                 * Try to reclaim some space by splitting a few
                 * large folios beyond i_size on the filesystem.
                 */
-               shmem_unused_huge_shrink(sbinfo, NULL, 2);
+               shmem_unused_huge_shrink(sbinfo, NULL, pages);
                /*
                 * And do a shmem_recalc_inode() to account for freed pages:
                 * except our folio is there in cache, so not quite balanced.