On Mon, Sep 16, 2019 at 11:42:37AM -0700, Darrick J. Wong wrote:
> On Mon, Sep 09, 2019 at 08:27:10PM +0200, Christoph Hellwig wrote:
<snip>
> > diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> > index 54c02aecf3cd..67efd86675e6 100644
> > --- a/fs/iomap/apply.c
> > +++ b/fs/iomap/apply.c
> > @@ -24,7 +24,9 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> > const struct iomap_ops *ops, void *data, iomap_actor_t actor)
> > {
> > struct iomap iomap = { 0 };
> > + struct iomap srcmap = { 0 };
> > loff_t written = 0, ret;
> > + u64 end;
> >
> > /*
> > * Need to map a range from start position for length bytes. This can
> > @@ -38,7 +40,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> > * expose transient stale data. If the reserve fails, we can safely
> > * back out at this point as there is nothing to undo.
> > */
> > - ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
> > + ret = ops->iomap_begin(inode, pos, length, flags, &iomap, &srcmap);
> > if (ret)
> > return ret;
> > if (WARN_ON(iomap.offset > pos))
> > @@ -50,15 +52,26 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> > * Cut down the length to the one actually provided by the filesystem,
> > * as it might not be able to give us the whole size that we requested.
> > */
> > - if (iomap.offset + iomap.length < pos + length)
> > - length = iomap.offset + iomap.length - pos;
> > + end = iomap.offset + iomap.length;
> > + if (srcmap.type)
>
> Do we need a "#define IOMAP_NULL 0" type to make this more explicit?
>
> Or at least a comment in iomap.h above the IOMAP_HOLE definition
> pointing out that type == 0 is valid for srcmap and not valid for iomap?
>
> Other than that the rest looks ok.
FWIW, my opinions about this have evolved since two days ago; please see
my reply to patch #12 about initializing @srcmap.type = IOMAP_HOLE and
using "type == IOMAP_HOLE" to decide if we're going to use the srcmap
for anything.
--D
> --D
>
> (This reminds me that at some point I ought to work on iomap debugging
> checks for the mappings returned by ->iomap_begin ...)
>
> > + end = min(end, srcmap.offset + srcmap.length);
> > + if (pos + length > end)
> > + length = end - pos;
> >
> > /*
> > - * Now that we have guaranteed that the space allocation will succeed.
> > + * Now that we have guaranteed that the space allocation will succeed,
> > * we can do the copy-in page by page without having to worry about
> > * failures exposing transient data.
> > + *
> > + * To support COW operations, we read in data for partially blocks from
> > + * the srcmap if the file system filled it in. In that case we the
> > + * length needs to be limited to the earlier of the ends of the iomaps.
> > + * If the file system did not provide a srcmap we pass in the normal
> > + * iomap into the actors so that they don't need to have special
> > + * handling for the two cases.
> > */
> > - written = actor(inode, pos, length, data, &iomap);
> > + written = actor(inode, pos, length, data, &iomap,
> > + srcmap.type ? &srcmap : &iomap);
> >
> > /*
> > * Now the data has been copied, commit the range we've copied. This
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index a421977a9496..58fb7a894ad4 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -219,7 +219,7 @@ static inline bool iomap_block_needs_zeroing(struct inode *inode,
> >
> > static loff_t
> > iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > - struct iomap *iomap)
> > + struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct iomap_readpage_ctx *ctx = data;
> > struct page *page = ctx->cur_page;
> > @@ -367,7 +367,7 @@ iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos,
> >
> > static loff_t
> > iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct iomap_readpage_ctx *ctx = data;
> > loff_t done, ret;
> > @@ -387,7 +387,7 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> > ctx->cur_page_in_bio = false;
> > }
> > ret = iomap_readpage_actor(inode, pos + done, length - done,
> > - ctx, iomap);
> > + ctx, iomap, srcmap);
> > }
> >
> > return done;
> > @@ -567,7 +567,7 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
> >
> > static int
> > __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> > - struct page *page, struct iomap *iomap)
> > + struct page *page, struct iomap *srcmap)
> > {
> > struct iomap_page *iop = iomap_page_create(inode, page);
> > loff_t block_size = i_blocksize(inode);
> > @@ -590,7 +590,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> > (to <= poff || to >= poff + plen))
> > continue;
> >
> > - if (iomap_block_needs_zeroing(inode, iomap, block_start)) {
> > + if (iomap_block_needs_zeroing(inode, srcmap, block_start)) {
> > if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
> > return -EIO;
> > zero_user_segments(page, poff, from, to, poff + plen);
> > @@ -599,7 +599,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> > }
> >
> > status = iomap_read_page_sync(block_start, page, poff, plen,
> > - iomap);
> > + srcmap);
> > if (status)
> > return status;
> > } while ((block_start += plen) < block_end);
> > @@ -609,13 +609,15 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> >
> > static int
> > iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> > - struct page **pagep, struct iomap *iomap)
> > + struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
> > {
> > const struct iomap_page_ops *page_ops = iomap->page_ops;
> > struct page *page;
> > int status = 0;
> >
> > BUG_ON(pos + len > iomap->offset + iomap->length);
> > + if (srcmap != iomap)
> > + BUG_ON(pos + len > srcmap->offset + srcmap->length);
> >
> > if (fatal_signal_pending(current))
> > return -EINTR;
> > @@ -633,13 +635,13 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> > goto out_no_page;
> > }
> >
> > - if (iomap->type == IOMAP_INLINE)
> > - iomap_read_inline_data(inode, page, iomap);
> > + if (srcmap->type == IOMAP_INLINE)
> > + iomap_read_inline_data(inode, page, srcmap);
> > else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> > - status = __block_write_begin_int(page, pos, len, NULL, iomap);
> > + status = __block_write_begin_int(page, pos, len, NULL, srcmap);
> > else
> > status = __iomap_write_begin(inode, pos, len, flags, page,
> > - iomap);
> > + srcmap);
> >
> > if (unlikely(status))
> > goto out_unlock;
> > @@ -725,16 +727,16 @@ iomap_write_end_inline(struct inode *inode, struct page *page,
> > }
> >
> > static int
> > -iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
> > - unsigned copied, struct page *page, struct iomap *iomap)
> > +iomap_write_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied,
> > + struct page *page, struct iomap *iomap, struct iomap *srcmap)
> > {
> > const struct iomap_page_ops *page_ops = iomap->page_ops;
> > loff_t old_size = inode->i_size;
> > int ret;
> >
> > - if (iomap->type == IOMAP_INLINE) {
> > + if (srcmap->type == IOMAP_INLINE) {
> > ret = iomap_write_end_inline(inode, page, iomap, pos, copied);
> > - } else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
> > + } else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
> > ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
> > page, NULL);
> > } else {
> > @@ -765,7 +767,7 @@ iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
> >
> > static loff_t
> > iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > - struct iomap *iomap)
> > + struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct iov_iter *i = data;
> > long status = 0;
> > @@ -799,7 +801,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > break;
> > }
> >
> > - status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
> > + status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap,
> > + srcmap);
> > if (unlikely(status))
> > break;
> >
> > @@ -810,8 +813,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> >
> > flush_dcache_page(page);
> >
> > - status = iomap_write_end(inode, pos, bytes, copied, page,
> > - iomap);
> > + status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
> > + srcmap);
> > if (unlikely(status < 0))
> > break;
> > copied = status;
> > @@ -864,7 +867,7 @@ EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
> >
> > static loff_t
> > iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > - struct iomap *iomap)
> > + struct iomap *iomap, struct iomap *srcmap)
> > {
> > long status = 0;
> > ssize_t written = 0;
> > @@ -873,7 +876,7 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > if (!(iomap->flags & IOMAP_F_SHARED))
> > return length;
> > /* don't bother with holes or unwritten extents */
> > - if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
> > + if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> > return length;
> >
> > do {
> > @@ -882,11 +885,12 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > struct page *page;
> >
> > status = iomap_write_begin(inode, pos, bytes,
> > - IOMAP_WRITE_F_UNSHARE, &page, iomap);
> > + IOMAP_WRITE_F_UNSHARE, &page, iomap, srcmap);
> > if (unlikely(status))
> > return status;
> >
> > - status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
> > + status = iomap_write_end(inode, pos, bytes, bytes, page, iomap,
> > + srcmap);
> > if (unlikely(status <= 0)) {
> > if (WARN_ON_ONCE(status == 0))
> > return -EIO;
> > @@ -925,19 +929,19 @@ iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
> > EXPORT_SYMBOL_GPL(iomap_file_unshare);
> >
> > static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
> > - unsigned bytes, struct iomap *iomap)
> > + unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct page *page;
> > int status;
> >
> > - status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
> > + status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap, srcmap);
> > if (status)
> > return status;
> >
> > zero_user(page, offset, bytes);
> > mark_page_accessed(page);
> >
> > - return iomap_write_end(inode, pos, bytes, bytes, page, iomap);
> > + return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
> > }
> >
> > static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
> > @@ -949,14 +953,14 @@ static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
> >
> > static loff_t
> > iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > bool *did_zero = data;
> > loff_t written = 0;
> > int status;
> >
> > /* already zeroed? we're done. */
> > - if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
> > + if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> > return count;
> >
> > do {
> > @@ -968,7 +972,8 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
> > if (IS_DAX(inode))
> > status = iomap_dax_zero(pos, offset, bytes, iomap);
> > else
> > - status = iomap_zero(inode, pos, offset, bytes, iomap);
> > + status = iomap_zero(inode, pos, offset, bytes, iomap,
> > + srcmap);
> > if (status < 0)
> > return status;
> >
> > @@ -1018,7 +1023,7 @@ EXPORT_SYMBOL_GPL(iomap_truncate_page);
> >
> > static loff_t
> > iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct page *page = data;
> > int ret;
> > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> > index 1fc28c2da279..e3ccbf7daaae 100644
> > --- a/fs/iomap/direct-io.c
> > +++ b/fs/iomap/direct-io.c
> > @@ -358,7 +358,7 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
> >
> > static loff_t
> > iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct iomap_dio *dio = data;
> >
> > diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
> > index f26fdd36e383..690ef2d7c6c8 100644
> > --- a/fs/iomap/fiemap.c
> > +++ b/fs/iomap/fiemap.c
> > @@ -44,7 +44,7 @@ static int iomap_to_fiemap(struct fiemap_extent_info *fi,
> >
> > static loff_t
> > iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > - struct iomap *iomap)
> > + struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct fiemap_ctx *ctx = data;
> > loff_t ret = length;
> > @@ -111,7 +111,7 @@ EXPORT_SYMBOL_GPL(iomap_fiemap);
> >
> > static loff_t
> > iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > sector_t *bno = data, addr;
> >
> > diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
> > index c04bad4b2b43..89f61d93c0bc 100644
> > --- a/fs/iomap/seek.c
> > +++ b/fs/iomap/seek.c
> > @@ -119,7 +119,7 @@ page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
> >
> > static loff_t
> > iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > switch (iomap->type) {
> > case IOMAP_UNWRITTEN:
> > @@ -165,7 +165,7 @@ EXPORT_SYMBOL_GPL(iomap_seek_hole);
> >
> > static loff_t
> > iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
> > - void *data, struct iomap *iomap)
> > + void *data, struct iomap *iomap, struct iomap *srcmap)
> > {
> > switch (iomap->type) {
> > case IOMAP_HOLE:
> > diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
> > index 152a230f668d..a648dbf6991e 100644
> > --- a/fs/iomap/swapfile.c
> > +++ b/fs/iomap/swapfile.c
> > @@ -76,7 +76,8 @@ static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
> > * distinction between written and unwritten extents.
> > */
> > static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
> > - loff_t count, void *data, struct iomap *iomap)
> > + loff_t count, void *data, struct iomap *iomap,
> > + struct iomap *srcmap)
> > {
> > struct iomap_swapfile_info *isi = data;
> > int error;
> > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> > index d340db666c06..f1c3ff27c666 100644
> > --- a/fs/xfs/xfs_iomap.c
> > +++ b/fs/xfs/xfs_iomap.c
> > @@ -928,7 +928,8 @@ xfs_file_iomap_begin(
> > loff_t offset,
> > loff_t length,
> > unsigned flags,
> > - struct iomap *iomap)
> > + struct iomap *iomap,
> > + struct iomap *srcmap)
> > {
> > struct xfs_inode *ip = XFS_I(inode);
> > struct xfs_mount *mp = ip->i_mount;
> > @@ -1154,7 +1155,8 @@ xfs_seek_iomap_begin(
> > loff_t offset,
> > loff_t length,
> > unsigned flags,
> > - struct iomap *iomap)
> > + struct iomap *iomap,
> > + struct iomap *srcmap)
> > {
> > struct xfs_inode *ip = XFS_I(inode);
> > struct xfs_mount *mp = ip->i_mount;
> > @@ -1240,7 +1242,8 @@ xfs_xattr_iomap_begin(
> > loff_t offset,
> > loff_t length,
> > unsigned flags,
> > - struct iomap *iomap)
> > + struct iomap *iomap,
> > + struct iomap *srcmap)
> > {
> > struct xfs_inode *ip = XFS_I(inode);
> > struct xfs_mount *mp = ip->i_mount;
> > diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> > index 3a0f0975a57e..6d795924baa7 100644
> > --- a/include/linux/iomap.h
> > +++ b/include/linux/iomap.h
> > @@ -127,7 +127,8 @@ struct iomap_ops {
> > * The actual length is returned in iomap->length.
> > */
> > int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
> > - unsigned flags, struct iomap *iomap);
> > + unsigned flags, struct iomap *iomap,
> > + struct iomap *srcmap);
> >
> > /*
> > * Commit and/or unreserve space previous allocated using iomap_begin.
> > @@ -143,7 +144,7 @@ struct iomap_ops {
> > * Main iomap iterator function.
> > */
> > typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
> > - void *data, struct iomap *iomap);
> > + void *data, struct iomap *iomap, struct iomap *srcmap);
> >
> > loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
> > unsigned flags, const struct iomap_ops *ops, void *data,
> > --
> > 2.20.1
> >
