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QjTdt1U34tYzac8Rbbj5Sc2N0iYZs7rIe+U/9wy+icbmazWQ/T8xA0i2VHXNo+Hgxac/MCd5TpHsa/9Jdp5/Y5eN9xhwHQ05sIGUc6Ffb7xL8AMsLU4c+X68sgybwIJrA7+9nRCjSyxstegEjEFK9iKJoNUDKwAt9x/x1tTVa3dJWbFlJHQNkhd7xuuD8bPPDz/Dkki70MpGFxyAwz8uYXTHpSUtaXOEIxpQklwNmLWmp/cNumQ2UT0K6shLT/Sd+tum1siMNOlsKwLDXSpi90Ffoy6Mdzv2J3cymw+LNKFH1vP26uhe5q8o0QUpYA8SY7DquElO9lcMGnMFHSW1gdQGDkQmyHTYVAMKhuo/rwu3rrXu+BpGdLMwxpQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 28 Feb 2025, at 11:35, Matthew Wilcox wrote: > On Fri, Feb 28, 2025 at 10:42:19AM -0500, Zi Yan wrote: >> @@ -524,7 +525,11 @@ static int __folio_migrate_mapping(struct address_s= pace *mapping, >> folio_set_swapcache(newfolio); >> newfolio->private =3D folio_get_private(folio); >> } >> - entries =3D nr; >> + /* shmem uses high-order entry */ >> + if (shmem_mapping(mapping)) > > It's be cheaper to check folio_test_anon() here, right? Yes and it gets rid of the new include. Let me send v2. > > Also, how did this bug remain unnoticed for almost 4 years? > Our testing is terrible ;-( Probably not 4 years. Before fc346d0a70a1 (2023), shmem was right, swap cache was wrong. After fc346d0a70a1, shmem is wrong, swap cache is right. And before Baolin=E2=80=99s patch, shmem only has PMD size folio to use multi-index entries. Maybe getting PMD size folio is really impossible when compaction runs a lot? > >> + entries =3D 1; >> + else >> + entries =3D nr; >> } else { >> VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); >> entries =3D 1; >> --=20 >> 2.47.2 >> Best Regards, Yan, Zi