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Revert "tmpfs: don't enable large folios if not supported"

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This reverts commit 5a90c155de.

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 5a90c155de has already been fixed by the following
commit 665575cff0 ("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 5a90c155de 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: 5a90c155de ("tmpfs: don't enable large folios if not supported")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baolin Wang 2026-04-23 09:41:42 +08:00 committed by Andrew Morton
parent b001cf7d16
commit eb92d97f7e
1 changed files with 1 additions and 4 deletions
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5
mm/shmem.c
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@ -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: