Am Fr., 23. Juli 2021 um 19:41 Uhr schrieb Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>: > Add support for reading inline data content into the page cache from > nonzero page-aligned file offsets. This enables the EROFS tailpacking > mode where the last few bytes of the file are stored right after the > inode. > > The buffered write path remains untouched since EROFS cannot be used > for testing. It'd be better to be implemented if upcoming real users > care and provide a real pattern rather than leave untested dead code > around. > > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Darrick J. Wong <djwong@xxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Andreas Gruenbacher <andreas.gruenbacher@xxxxxxxxx> > Tested-by: Huang Jianan <huangjianan@xxxxxxxx> # erofs > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> > --- > v6: https://lore.kernel.org/r/20210722031729.51628-1-hsiangkao@xxxxxxxxxxxxxxxxx > changes since v6: > - based on Christoph's reply; > - update commit message suggested by Darrick; > - disable buffered write path until some real fs users. > > fs/iomap/buffered-io.c | 42 ++++++++++++++++++++++++++---------------- > fs/iomap/direct-io.c | 10 ++++++---- > include/linux/iomap.h | 14 ++++++++++++++ > 3 files changed, 46 insertions(+), 20 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 87ccb3438bec..f351e1f9e3f6 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -205,25 +205,29 @@ struct iomap_readpage_ctx { > struct readahead_control *rac; > }; > > -static void > -iomap_read_inline_data(struct inode *inode, struct page *page, > - struct iomap *iomap) > +static int iomap_read_inline_data(struct inode *inode, struct page *page, > + struct iomap *iomap, loff_t pos) This is completely broken. This function is about filling the page cache. All the information needed for that is in struct iomap; the start position of an iomap operation has nothing to do with it. > { > - size_t size = i_size_read(inode); > + size_t size = iomap->length + iomap->offset - pos; > void *addr; > > if (PageUptodate(page)) > - return; > + return PAGE_SIZE; > > - 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(pos))) > + return -EIO; > + if (WARN_ON_ONCE(!iomap_inline_data_size_valid(iomap))) > + return -EIO; > + if (WARN_ON_ONCE(page_has_private(page))) > + return -EIO; > > addr = kmap_atomic(page); > - memcpy(addr, iomap->inline_data, size); > + memcpy(addr, iomap_inline_buf(iomap, pos), size); > memset(addr + size, 0, PAGE_SIZE - size); > kunmap_atomic(addr); > SetPageUptodate(page); > + return PAGE_SIZE; > } > > static inline bool iomap_block_needs_zeroing(struct inode *inode, > @@ -246,11 +250,8 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > unsigned poff, plen; > sector_t sector; > > - if (iomap->type == IOMAP_INLINE) { > - WARN_ON_ONCE(pos); > - iomap_read_inline_data(inode, page, iomap); > - return PAGE_SIZE; > - } > + if (iomap->type == IOMAP_INLINE) > + return iomap_read_inline_data(inode, page, iomap, pos); > > /* zero post-eof blocks as the page may be mapped */ > iop = iomap_page_create(inode, page); > @@ -589,6 +590,15 @@ __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, 0); > +} > + > static int > iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > struct page **pagep, struct iomap *iomap, struct iomap *srcmap) > @@ -618,14 +628,14 @@ 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 > status = __iomap_write_begin(inode, pos, len, flags, page, > srcmap); > > - if (unlikely(status)) > + if (unlikely(status < 0)) > goto out_unlock; > > *pagep = page; > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 9398b8c31323..a6aaea2764a5 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 *dst = iomap_inline_buf(iomap, pos); > size_t copied; > > - BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data)); > + if (WARN_ON_ONCE(!iomap_inline_data_size_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_buf(iomap, size), 0, pos - size); > + copied = copy_from_iter(dst, 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(dst, length, iter); > } > dio->size += copied; > return copied; > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 479c1da3e221..56b118c6d05c 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -97,6 +97,20 @@ iomap_sector(struct iomap *iomap, loff_t pos) > return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT; > } > > +static inline void *iomap_inline_buf(const struct iomap *iomap, loff_t pos) > +{ > + return iomap->inline_data - iomap->offset + pos; > +} > + > +/* > + * iomap->inline_data is a potentially kmapped page, ensure it never crosses a > + * page boundary. > + */ > +static inline bool iomap_inline_data_size_valid(const 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
