On Mon, Apr 13, 2026 at 03:20:24PM -0400, Zi Yan wrote: > They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without > large folio support, so that read-only THPs created in these FSes are not > seen by the FSes when the underlying fd becomes writable. Now read-only PMD > THPs only appear in a FS with large folio support and the supported orders > include PMD_ORDRE. > > READ_ONLY_THP_FOR_FS was using mapping->nr_thps, inode->i_writecount, and > smp_mb() to prevent writes to a read-only THP and collapsing writable > folios into a THP. In collapse_file(), mapping->nr_thps is increased, then > smp_mb(), and if inode->i_writecount > 0, collapse is stopped, while > do_dentry_open() first increases inode->i_writecount, then a full memory > fence, and if mapping->nr_thps > 0, all read-only THPs are truncated. > > Now this mechanism can be removed along with READ_ONLY_THP_FOR_FS code, > since a dirty folio check has been added after try_to_unmap() and > try_to_unmap_flush() in collapse_file() to make sure no writable folio can > be collapsed. > > Signed-off-by: Zi Yan <[email protected]> > --- > fs/open.c | 27 --------------------------- > include/linux/pagemap.h | 29 ----------------------------- > mm/filemap.c | 1 - > mm/huge_memory.c | 1 - > mm/khugepaged.c | 28 ---------------------------- > 5 files changed, 86 deletions(-)
This is great. Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
