On Thu, Nov 9, 2023 at 10:54 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > The patch titled > Subject: mm: add folio_zero_tail() and use it in ext4 > has been added to the -mm mm-unstable branch. Its filename is > mm-add-folio_zero_tail-and-use-it-in-ext4.patch > > This patch will shortly appear at > https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-folio_zero_tail-and-use-it-in-ext4.patch > > This patch will later appear in the mm-unstable branch at > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > The -mm tree is included into linux-next via the mm-everything > branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > and is updated there every 2-3 working days > > ------------------------------------------------------ > From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> > Subject: mm: add folio_zero_tail() and use it in ext4 > Date: Tue, 7 Nov 2023 21:26:40 +0000 > > Patch series "Add folio_zero_tail() and folio_fill_tail()". > > I'm trying to make it easier for filesystems with tailpacking / stuffing / > inline data to use folios. The primary function here is > folio_fill_tail(). You give it a pointer to memory where the data > currently is, and it takes care of copying it into the folio at that > offset. That works for gfs2 & iomap. Then There's Ext4. Rather than gin > up some kind of specialist "Here's a two pointers to two blocks of memory" > routine, just let it do its current thing, and let it call > folio_zero_tail(), which is also called by folio_fill_tail(). > > Other filesystems can be converted later; these ones seemed like good > examples as they're already partly or completely converted to folios. > > > This patch (of 3): > > Instead of unmapping the folio after copying the data to it, then mapping > it again to zero the tail, provide folio_zero_tail() to zero the tail of > an already-mapped folio. > > Link: https://lkml.kernel.org/r/20231107212643.3490372-1-willy@xxxxxxxxxxxxx > Link: https://lkml.kernel.org/r/20231107212643.3490372-2-willy@xxxxxxxxxxxxx > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx> > Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx> > Cc: Darrick J. Wong <djwong@xxxxxxxxxx> > Cc: Theodore Ts'o <tytso@xxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > fs/ext4/inline.c | 3 +-- > include/linux/highmem.h | 38 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 39 insertions(+), 2 deletions(-) > > --- a/fs/ext4/inline.c~mm-add-folio_zero_tail-and-use-it-in-ext4 > +++ a/fs/ext4/inline.c > @@ -502,9 +502,8 @@ static int ext4_read_inline_folio(struct > BUG_ON(len > PAGE_SIZE); > kaddr = kmap_local_folio(folio, 0); > ret = ext4_read_inline_data(inode, kaddr, len, &iloc); > - flush_dcache_folio(folio); > + kaddr = folio_zero_tail(folio, len, kaddr + len); > kunmap_local(kaddr); > - folio_zero_segment(folio, len, folio_size(folio)); > folio_mark_uptodate(folio); > brelse(iloc.bh); > > --- a/include/linux/highmem.h~mm-add-folio_zero_tail-and-use-it-in-ext4 > +++ a/include/linux/highmem.h > @@ -484,6 +484,44 @@ static inline void memcpy_to_folio(struc > } > > /** > + * folio_zero_tail - Zero the tail of a folio. > + * @folio: The folio to zero. > + * @kaddr: The address the folio is currently mapped to. > + * @offset: The byte offset in the folio to start zeroing at. And the order of the arguments in the description is still wrong. > + * > + * If you have already used kmap_local_folio() to map a folio, written > + * some data to it and now need to zero the end of the folio (and flush > + * the dcache), you can use this function. If you do not have the > + * folio kmapped (eg the folio has been partially populated by DMA), > + * use folio_zero_range() or folio_zero_segment() instead. > + * > + * Return: An address which can be passed to kunmap_local(). > + */ > +static inline __must_check void *folio_zero_tail(struct folio *folio, > + size_t offset, void *kaddr) > +{ > + size_t len = folio_size(folio) - offset; > + > + if (folio_test_highmem(folio)) { > + size_t max = PAGE_SIZE - offset_in_page(offset); > + > + while (len > max) { > + memset(kaddr, 0, max); > + kunmap_local(kaddr); > + len -= max; > + offset += max; > + max = PAGE_SIZE; > + kaddr = kmap_local_folio(folio, offset); > + } > + } > + > + memset(kaddr, 0, len); > + flush_dcache_folio(folio); > + > + return kaddr; > +} > + > +/** > * memcpy_from_file_folio - Copy some bytes from a file folio. > * @to: The destination buffer. > * @folio: The folio to copy from. > _ > > Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are > > mm-add-folio_zero_tail-and-use-it-in-ext4.patch > mm-add-folio_fill_tail-and-use-it-in-iomap.patch > gfs2-convert-stuffed_readpage-to-stuffed_read_folio.patch > mm-remove-test_set_page_writeback.patch > afs-do-not-test-the-return-value-of-folio_start_writeback.patch > smb-do-not-test-the-return-value-of-folio_start_writeback.patch > mm-return-void-from-folio_start_writeback-and-related-functions.patch > mm-make-mapping_evict_folio-the-preferred-way-to-evict-clean-folios.patch > mm-convert-__do_fault-to-use-a-folio.patch > mm-use-mapping_evict_folio-in-truncate_error_page.patch > mm-convert-soft_offline_in_use_page-to-use-a-folio.patch > mm-convert-isolate_page-to-mf_isolate_folio.patch > mm-remove-invalidate_inode_page.patch > Thanks, Andreas
