Hi Darrick, On Mon, Jul 26, 2021 at 03:10:54PM -0700, Darrick J. Wong wrote: > On Mon, Jul 26, 2021 at 10:57:34PM +0800, Gao Xiang wrote: > > The existing inline data support only works for cases where the entire > > file is stored as inline data. For larger files, EROFS stores the > > initial blocks separately and then can pack a small tail adjacent to the > > inode. Generalise inline data to allow for tail packing. Tails may not > > cross a page boundary in memory. > > > > We currently have no filesystems that support tail packing and writing, > > so that case is currently disabled (see iomap_write_begin_inline). > > > > Cc: Christoph Hellwig <hch@xxxxxx> > > Cc: Darrick J. Wong <djwong@xxxxxxxxxx> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> > > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> > > --- > > v7: https://lore.kernel.org/r/20210723174131.180813-1-hsiangkao@xxxxxxxxxxxxxxxxx > > changes since v7: > > - This version is based on Andreas's patch, the main difference > > is to avoid using "iomap->length" in iomap_read_inline_data(). > > more details see: > > https://lore.kernel.org/r/CAHpGcMJhuSApy4eg9jKe2pYq4d7bY-Lg-Bmo9tOANghQ2Hxo-A@xxxxxxxxxxxxxx > > The rest are similar (some renaming and return type changes.) > > > > - with update according to Christoph's comments: > > https://lore.kernel.org/r/20210726121702.GA528@xxxxxx/ > > except that " > > I think we should fix that now that we have the srcmap concept. > > That is or IOMAP_WRITE|IOMAP_ZERO return the inline map as the > > soure map, and return the actual block map we plan to write into > > as the main iomap. " > > Hopefully it could be addressed with a new gfs2-related patch. > > > > - it passes gfs2 fstests and no strange on my side. > > > > Hopefully I don't miss anything (already many inputs), and everyone > > is happy with this version. > > > > fs/iomap/buffered-io.c | 40 ++++++++++++++++++++++++++++------------ > > fs/iomap/direct-io.c | 10 ++++++---- > > include/linux/iomap.h | 18 ++++++++++++++++++ > > 3 files changed, 52 insertions(+), 16 deletions(-) > > > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > > index 87ccb3438bec..0d9f161ecb7e 100644 > > --- a/fs/iomap/buffered-io.c > > +++ b/fs/iomap/buffered-io.c > > @@ -205,25 +205,30 @@ struct iomap_readpage_ctx { > > struct readahead_control *rac; > > }; > > > > -static void > > -iomap_read_inline_data(struct inode *inode, struct page *page, > > +static int iomap_read_inline_data(struct inode *inode, struct page *page, > > struct iomap *iomap) > > { > > - size_t size = i_size_read(inode); > > + size_t size = i_size_read(inode) - iomap->offset; > > void *addr; > > > > if (PageUptodate(page)) > > - return; > > + return 0; > > > > - BUG_ON(page_has_private(page)); > > - BUG_ON(page->index); > > - BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data)); > > + /* inline data must start page aligned in the file */ > > + if (WARN_ON_ONCE(offset_in_page(iomap->offset))) > > + return -EIO; > > + if (WARN_ON_ONCE(size > PAGE_SIZE - > > + offset_in_page(iomap->inline_data))) > > + return -EIO; > > + if (WARN_ON_ONCE(page_has_private(page))) > > + return -EIO; > > > > addr = kmap_atomic(page); > > memcpy(addr, iomap->inline_data, size); > > memset(addr + size, 0, PAGE_SIZE - size); > > kunmap_atomic(addr); > > SetPageUptodate(page); > > + return 0; > > As I muttered in the v7 thread, I don't really like how this function > gets away from using iomap->length for the copy length, unlike the other > iomap read paths. I started sketching out how I'd really like the > function to read and ended up with: > > static int iomap_read_inline_data(struct inode *inode, struct page *page, > struct iomap *iomap) > { > void *addr; > loff_t isize = i_size_read(inode); > loff_t ret; > unsigned int plen = min(isize - iomap->offset, iomap->length); > > /* inline data must start page aligned in the file */ > if (WARN_ON_ONCE(offset_in_page(iomap->offset))) > return -EIO; > if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap))) > return -EIO; > if (WARN_ON_ONCE(page_has_private(page))) > return -EIO; > > addr = kmap_atomic(page); > memcpy(addr, iomap->inline_data, plen); > if (iomap->offset + plen == isize) { > /* If we reach EOF, we can zero the rest of the page */ > memset(addr + plen, 0, PAGE_SIZE - plen); > plen = PAGE_SIZE; > } > > if (offset_in_page(iomap->offset) == 0 && plen == PAGE_SIZE) { > SetPageUptodate(page); > } else { > iomap_page_create(inode, page); > iomap_set_range_uptodate(page, > offset_in_page(iomap->offset), plen); If we finally do like this, I think `plen' here needs to be block-aligned like my previous patches. Another point is currently these code has no use cases, so let's do the minimal thing first. (I could try this when working on subpage-sized block support.) > } > kunmap_atomic(addr); > return plen; > } > > But then my brain filled up with all the other potential case I'd have > to support in order to do this properly, and decided that this patch, > while retaining some grossness, isn't really any worse that what we have > now. Yeah. > > I think I /would/ like to request a V9 with one extra safety check, > however: > > if (WARN_ON_ONCE(size > iomap->length)) > return -EIO; > > Add that one sanity check and I think I'm willing to throw this on the > pile for 5.15. Okay, will update. Thanks, Gao Xiang > > --D > > > } > > > > static inline bool iomap_block_needs_zeroing(struct inode *inode, > > @@ -247,8 +252,10 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > > sector_t sector; > > > > if (iomap->type == IOMAP_INLINE) { > > - WARN_ON_ONCE(pos); > > - iomap_read_inline_data(inode, page, iomap); > > + int ret = iomap_read_inline_data(inode, page, iomap); > > + > > + if (ret) > > + return ret; > > return PAGE_SIZE; > > } > > > > @@ -589,6 +596,15 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags, > > return 0; > > } > > > > +static int iomap_write_begin_inline(struct inode *inode, > > + struct page *page, struct iomap *srcmap) > > +{ > > + /* needs more work for the tailpacking case, disable for now */ > > + if (WARN_ON_ONCE(srcmap->offset != 0)) > > + return -EIO; > > + return iomap_read_inline_data(inode, page, srcmap); > > +} > > + > > static int > > iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > > struct page **pagep, struct iomap *iomap, struct iomap *srcmap) > > @@ -618,7 +634,7 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > > } > > > > if (srcmap->type == IOMAP_INLINE) > > - iomap_read_inline_data(inode, page, srcmap); > > + status = iomap_write_begin_inline(inode, page, srcmap); > > else if (iomap->flags & IOMAP_F_BUFFER_HEAD) > > status = __block_write_begin_int(page, pos, len, NULL, srcmap); > > else > > @@ -671,11 +687,11 @@ static size_t iomap_write_end_inline(struct inode *inode, struct page *page, > > void *addr; > > > > WARN_ON_ONCE(!PageUptodate(page)); > > - BUG_ON(pos + copied > PAGE_SIZE - offset_in_page(iomap->inline_data)); > > + BUG_ON(!iomap_inline_data_valid(iomap)); > > > > flush_dcache_page(page); > > addr = kmap_atomic(page); > > - memcpy(iomap->inline_data + pos, addr + pos, copied); > > + memcpy(iomap_inline_data(iomap, pos), addr + pos, copied); > > kunmap_atomic(addr); > > > > mark_inode_dirty(inode); > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > > index 9398b8c31323..41ccbfc9dc82 100644 > > --- a/fs/iomap/direct-io.c > > +++ b/fs/iomap/direct-io.c > > @@ -378,23 +378,25 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length, > > struct iomap_dio *dio, struct iomap *iomap) > > { > > struct iov_iter *iter = dio->submit.iter; > > + void *inline_data = iomap_inline_data(iomap, pos); > > size_t copied; > > > > - BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data)); > > + if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap))) > > + return -EIO; > > > > if (dio->flags & IOMAP_DIO_WRITE) { > > loff_t size = inode->i_size; > > > > if (pos > size) > > - memset(iomap->inline_data + size, 0, pos - size); > > - copied = copy_from_iter(iomap->inline_data + pos, length, iter); > > + memset(iomap_inline_data(iomap, size), 0, pos - size); > > + copied = copy_from_iter(inline_data, length, iter); > > if (copied) { > > if (pos + copied > size) > > i_size_write(inode, pos + copied); > > mark_inode_dirty(inode); > > } > > } else { > > - copied = copy_to_iter(iomap->inline_data + pos, length, iter); > > + copied = copy_to_iter(inline_data, length, iter); > > } > > dio->size += copied; > > return copied; > > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > > index 479c1da3e221..b8ec145b2975 100644 > > --- a/include/linux/iomap.h > > +++ b/include/linux/iomap.h > > @@ -97,6 +97,24 @@ iomap_sector(struct iomap *iomap, loff_t pos) > > return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT; > > } > > > > +/* > > + * Returns the inline data pointer for logical offset @pos. > > + */ > > +static inline void *iomap_inline_data(struct iomap *iomap, loff_t pos) > > +{ > > + return iomap->inline_data + pos - iomap->offset; > > +} > > + > > +/* > > + * Check if the mapping's length is within the valid range for inline data. > > + * This is used to guard against accessing data beyond the page inline_data > > + * points at. > > + */ > > +static inline bool iomap_inline_data_valid(struct iomap *iomap) > > +{ > > + return iomap->length <= PAGE_SIZE - offset_in_page(iomap->inline_data); > > +} > > + > > /* > > * When a filesystem sets page_ops in an iomap mapping it returns, page_prepare > > * and page_done will be called for each page written to. This only applies to > > -- > > 2.24.4 > >
