| Message ID | 20240405180038.2618624-1-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: Convert pagecache_isize_extended to use a folio | expand |
On 05.04.24 20:00, Matthew Wilcox (Oracle) wrote: > Remove four hidden calls to compound_head(). Also exit early if the > filesystem block size is >= PAGE_SIZE instead of just equal to PAGE_SIZE. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com> > --- > mm/truncate.c | 36 +++++++++++++++++------------------- > 1 file changed, 17 insertions(+), 19 deletions(-) > > diff --git a/mm/truncate.c b/mm/truncate.c > index 725b150e47ac..e99085bf3d34 100644 > --- a/mm/truncate.c > +++ b/mm/truncate.c > @@ -764,15 +764,15 @@ EXPORT_SYMBOL(truncate_setsize); > * @from: original inode size > * @to: new inode size > * > - * Handle extension of inode size either caused by extending truncate or by > - * write starting after current i_size. We mark the page straddling current > - * i_size RO so that page_mkwrite() is called on the nearest write access to > - * the page. This way filesystem can be sure that page_mkwrite() is called on > - * the page before user writes to the page via mmap after the i_size has been > - * changed. > + * Handle extension of inode size either caused by extending truncate or > + * by write starting after current i_size. We mark the page straddling > + * current i_size RO so that page_mkwrite() is called on the first > + * write access to the page. The filesystem will update its per-block > + * information before user writes to the page via mmap after the i_size > + * has been changed. Did you intend not to s/page/folio/ ? > * > * The function must be called after i_size is updated so that page fault > - * coming after we unlock the page will already see the new i_size. > + * coming after we unlock the folio will already see the new i_size. > * The function must be called while we still hold i_rwsem - this not only > * makes sure i_size is stable but also that userspace cannot observe new > * i_size value before we are prepared to store mmap writes at new inode size. > @@ -781,31 +781,29 @@ void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to) Reviewed-by: David Hildenbrand <david@redhat.com>
On Tue, Apr 09, 2024 at 03:39:35PM +0200, David Hildenbrand wrote: > On 05.04.24 20:00, Matthew Wilcox (Oracle) wrote: > > + * Handle extension of inode size either caused by extending truncate or > > + * by write starting after current i_size. We mark the page straddling > > + * current i_size RO so that page_mkwrite() is called on the first > > + * write access to the page. The filesystem will update its per-block > > + * information before user writes to the page via mmap after the i_size > > + * has been changed. > > Did you intend not to s/page/folio/ ? I did! I think here we're talking about page faults, and we can control the RO property on a per-PTE (ie per-page) basis. Do you think it'd be clearer if we talked about folios here? We're in a bit of an interesting spot because filesystems generally don't have folios which overhang the end of the file by more than a page. It can happen if truncate fails to split a folio. > Reviewed-by: David Hildenbrand <david@redhat.com> Thanks!
diff --git a/mm/truncate.c b/mm/truncate.c index 725b150e47ac..e99085bf3d34 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -764,15 +764,15 @@ EXPORT_SYMBOL(truncate_setsize); * @from: original inode size * @to: new inode size * - * Handle extension of inode size either caused by extending truncate or by - * write starting after current i_size. We mark the page straddling current - * i_size RO so that page_mkwrite() is called on the nearest write access to - * the page. This way filesystem can be sure that page_mkwrite() is called on - * the page before user writes to the page via mmap after the i_size has been - * changed. + * Handle extension of inode size either caused by extending truncate or + * by write starting after current i_size. We mark the page straddling + * current i_size RO so that page_mkwrite() is called on the first + * write access to the page. The filesystem will update its per-block + * information before user writes to the page via mmap after the i_size + * has been changed. * * The function must be called after i_size is updated so that page fault - * coming after we unlock the page will already see the new i_size. + * coming after we unlock the folio will already see the new i_size. * The function must be called while we still hold i_rwsem - this not only * makes sure i_size is stable but also that userspace cannot observe new * i_size value before we are prepared to store mmap writes at new inode size. @@ -781,31 +781,29 @@ void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to) { int bsize = i_blocksize(inode); loff_t rounded_from; - struct page *page; - pgoff_t index; + struct folio *folio; WARN_ON(to > inode->i_size); - if (from >= to || bsize == PAGE_SIZE) + if (from >= to || bsize >= PAGE_SIZE) return; /* Page straddling @from will not have any hole block created? */ rounded_from = round_up(from, bsize); if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1))) return; - index = from >> PAGE_SHIFT; - page = find_lock_page(inode->i_mapping, index); - /* Page not cached? Nothing to do */ - if (!page) + folio = filemap_lock_folio(inode->i_mapping, from / PAGE_SIZE); + /* Folio not cached? Nothing to do */ + if (IS_ERR(folio)) return; /* - * See clear_page_dirty_for_io() for details why set_page_dirty() + * See folio_clear_dirty_for_io() for details why folio_mark_dirty() * is needed. */ - if (page_mkclean(page)) - set_page_dirty(page); - unlock_page(page); - put_page(page); + if (folio_mkclean(folio)) + folio_mark_dirty(folio); + folio_unlock(folio); + folio_put(folio); } EXPORT_SYMBOL(pagecache_isize_extended);