On Tue, Jul 27, 2021 at 5:00 AM Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> 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: Darrick J. Wong <djwong@xxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> > --- > v8: https://lore.kernel.org/r/20210726145734.214295-1-hsiangkao@xxxxxxxxxxxxxxxxx > changes since v8: > - update the subject to 'iomap: Support file tail packing' as there > are clearly a number of ways to make the inline data support more > flexible (Matthew); > > - add one extra safety check (Darrick): > if (WARN_ON_ONCE(size > iomap->length)) > return -EIO; > > fs/iomap/buffered-io.c | 42 ++++++++++++++++++++++++++++++------------ > fs/iomap/direct-io.c | 10 ++++++---- > include/linux/iomap.h | 18 ++++++++++++++++++ > 3 files changed, 54 insertions(+), 16 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 87ccb3438bec..f429b9d87dbe 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -205,25 +205,32 @@ 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(size > iomap->length)) > + 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; > } > > static inline bool iomap_block_needs_zeroing(struct inode *inode, > @@ -247,8 +254,10 @@ 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 +598,15 @@ __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 */ Nit: the comma should be a semicolon or period here. > + 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 +636,7 @@ 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 +689,11 @@ 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 > Andreas
