On Fri, Aug 02, 2019 at 05:00:36PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> Introduces a new type IOMAP_COW, which means the data at offset
> must be read from a srcmap and copied before performing the
> write on the offset.
>
> The srcmap is used to identify where the read is to be performed
> from. This is passed to iomap->begin() of the respective
> filesystem, which is supposed to put in the details for
> reading before performing the copy for CoW.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/dax.c | 8 +++++---
> fs/ext2/inode.c | 2 +-
> fs/ext4/inode.c | 2 +-
> fs/gfs2/bmap.c | 3 ++-
> fs/iomap/apply.c | 5 +++--
> fs/iomap/buffered-io.c | 14 +++++++-------
> fs/iomap/direct-io.c | 2 +-
> fs/iomap/fiemap.c | 4 ++--
> fs/iomap/seek.c | 4 ++--
> fs/iomap/swapfile.c | 3 ++-
> fs/xfs/xfs_iomap.c | 9 ++++++---
> include/linux/iomap.h | 6 ++++--
> 12 files changed, 36 insertions(+), 26 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index a237141d8787..b21d9a9cde2b 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1090,7 +1090,7 @@ EXPORT_SYMBOL_GPL(__dax_zero_page_range);
>
> static loff_t
> dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> - struct iomap *iomap)
> + struct iomap *iomap, struct iomap *srcmap)
> {
> struct block_device *bdev = iomap->bdev;
> struct dax_device *dax_dev = iomap->dax_dev;
> @@ -1248,6 +1248,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> unsigned long vaddr = vmf->address;
> loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
> struct iomap iomap = { 0 };
> + struct iomap srcmap = { 0 };
> unsigned flags = IOMAP_FAULT;
> int error, major = 0;
> bool write = vmf->flags & FAULT_FLAG_WRITE;
> @@ -1292,7 +1293,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> * the file system block size to be equal the page size, which means
> * that we never have to deal with more than a single extent here.
> */
> - error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
> + error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap, &srcmap);
> if (iomap_errp)
> *iomap_errp = error;
> if (error) {
> @@ -1472,6 +1473,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
> struct inode *inode = mapping->host;
> vm_fault_t result = VM_FAULT_FALLBACK;
> struct iomap iomap = { 0 };
> + struct iomap srcmap = { 0 };
> pgoff_t max_pgoff;
> void *entry;
> loff_t pos;
> @@ -1546,7 +1548,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
> * to look up our filesystem block.
> */
> pos = (loff_t)xas.xa_index << PAGE_SHIFT;
> - error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
> + error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap, &srcmap);
/me wonders aloud if he ought to add a helper function to standardize at
least some of validation of the iomap that gets returned from
->iomap_begin invocations...
> if (error)
> goto unlock_entry;
>
<snip>
> diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> index 54c02aecf3cd..6cdb362fff36 100644
> --- a/fs/iomap/apply.c
> +++ b/fs/iomap/apply.c
> @@ -24,6 +24,7 @@ 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;
>
> /*
> @@ -38,7 +39,7 @@ 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))
...because I wonder if we ought to have a debugging assert here just in
case an ->iomap_begin returns IOMAP_COW in response to an IOMAP_WRITE
request? Basic sanity checks to catch accidental API misuse, etc.
Eh we probably ought to have a CONFIG_IOMAP_DEBUG so that non-developers
don't necessarily have to pay the assert costs or something like that.
> @@ -58,7 +59,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> * we can do the copy-in page by page without having to worry about
> * failures exposing transient data.
> */
> - written = actor(inode, pos, length, data, &iomap);
> + written = actor(inode, pos, length, data, &iomap, &srcmap);
>
> /*
> * 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 e25901ae3ff4..f27756c0b31c 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -205,7 +205,7 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
>
> 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;
> @@ -351,7 +351,7 @@ 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;
> @@ -371,7 +371,7 @@ 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;
> @@ -736,7 +736,7 @@ 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;
> @@ -853,7 +853,7 @@ __iomap_read_page(struct inode *inode, loff_t offset)
>
> static loff_t
> iomap_dirty_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;
> @@ -942,7 +942,7 @@ 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;
> @@ -1011,7 +1011,7 @@ 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 10517cea9682..5279029c7a3c 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -362,7 +362,7 @@ 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)
> 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)
The switch(iomap->type) probably ought to have a separate printk for the
IOMAP_COW case so that we don't go complaining about "unwritten" extents
in the swap file.
> {
> struct iomap_swapfile_info *isi = data;
> int error;
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 3a4310d7cb59..8321733c16c3 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -922,7 +922,8 @@ 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;
> @@ -1145,7 +1146,8 @@ 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;
> @@ -1231,7 +1233,8 @@ 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;
XFS part looks ok... I guess I'll get to Shiyuan's series next.
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index bc499ceae392..5b2055e8ca8a 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -26,6 +26,7 @@ struct vm_fault;
> #define IOMAP_MAPPED 0x03 /* blocks allocated at @addr */
> #define IOMAP_UNWRITTEN 0x04 /* blocks allocated at @addr in unwritten state */
> #define IOMAP_INLINE 0x05 /* data inline in the inode */
> +#define IOMAP_COW 0x06 /* copy data from srcmap before writing */
Hm, ok, at least the comment references that this is only for writes.
Looks good!
--D
>
> /*
> * Flags for all iomap mappings:
> @@ -110,7 +111,8 @@ 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.
> @@ -126,7 +128,7 @@ 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,
> --
> 2.16.4
>
