From: Baolin Wang Date: Thu, 23 Apr 2026 01:41:42 +0000 (+0800) Subject: Revert "tmpfs: don't enable large folios if not supported" X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eb92d97f7e6a325607b9c3981131067c0469bfcf;p=thirdparty%2Fkernel%2Flinux.git Revert "tmpfs: don't enable large folios if not supported" This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c. Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to determine whether the shmem mount supports large folios. However, for anonymous shmem, whether it supports large folios can be dynamically configured via sysfs interfaces, so setting or not setting mapping_set_large_folios() during initialization cannot accurately reflect whether anonymous shmem actually supports large folios, which has already caused some confusion[1]. Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios() setting consistent across all mappings in the entire tmpfs mount. In other words, under the same tmpfs mount, after remount, we might end up with some mappings supporting large folios (calling mapping_set_large_folios()) while others don't. After some investigation, I found that the write performance regression addressed by commit 5a90c155defa has already been fixed by the following commit 665575cff098b ("filemap: move prefaulting out of hot write path"). See the following test data: Base: dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s ) dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) Base + revert 5a90c155defa: dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s) dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) The data is basically consistent with minor fluctuation noise. So we can now safely revert commit 5a90c155defa to set mapping_set_large_folios() for all shmem mounts unconditionally. Link: https://lore.kernel.org/b2c7deee259a94b0d00a7c320d8d24d2c421f761.1776908112.git.baolin.wang@linux.alibaba.com Link: https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/ [1] Link: https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/ Fixes: 5a90c155defa ("tmpfs: don't enable large folios if not supported") Signed-off-by: Baolin Wang Acked-by: Zi Yan Reviewed-by: Kefeng Wang Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Acked-by: Lorenzo Stoakes Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- diff --git a/mm/shmem.c b/mm/shmem.c index 3b5dc21b323c..bab3529af23c 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3101,10 +3101,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, cache_no_acl(inode); if (sbinfo->noswap) mapping_set_unevictable(inode->i_mapping); - - /* Don't consider 'deny' for emergencies and 'force' for testing */ - if (sbinfo->huge) - mapping_set_large_folios(inode->i_mapping); + mapping_set_large_folios(inode->i_mapping); switch (mode & S_IFMT) { default: