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iomap: use a srcmap for a read-modify-write I/O 

The srcmap is used to identify where the read is to be performed from.
It is passed to ->iomap_begin, which can fill it in if we need to read
data for partially written blocks from a different location than the
write target.  The srcmap is only supported for buffered writes so far.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
[hch: merged two patches, removed the IOMAP_F_COW flag, use iomap as
      srcmap if not set, adjust length down to srcmap end as well]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
This commit is contained in:
Goldwyn Rodrigues 2019-10-18 16:44:10 -07:00 committed by Darrick J. Wong
parent eb81cf9d0e
commit c039b99792
12 changed files with 82 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
fs/dax.c
View File

@ -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;
@ -1247,7 +1247,8 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
struct inode *inode = mapping->host;
unsigned long vaddr = vmf->address;
loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
struct iomap iomap = { 0 };
struct iomap iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
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) {
@ -1471,7 +1472,8 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
struct inode *inode = mapping->host;
vm_fault_t result = VM_FAULT_FALLBACK;
struct iomap iomap = { 0 };
struct iomap iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
pgoff_t max_pgoff;
void *entry;
loff_t pos;
@ -1546,7 +1548,8 @@ 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);
if (error)
goto unlock_entry;

2
fs/ext2/inode.c
View File

@ -801,7 +801,7 @@ int ext2_get_block(struct inode *inode, sector_t iblock,
#ifdef CONFIG_FS_DAX
static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned flags, struct iomap *iomap)
unsigned flags, struct iomap *iomap, struct iomap *srcmap)
{
unsigned int blkbits = inode->i_blkbits;
unsigned long first_block = offset >> blkbits;

2
fs/ext4/inode.c
View File

@ -3407,7 +3407,7 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
}
static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned flags, struct iomap *iomap)
unsigned flags, struct iomap *iomap, struct iomap *srcmap)
{
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
unsigned int blkbits = inode->i_blkbits;

3
fs/gfs2/bmap.c
View File

@ -1149,7 +1149,8 @@ static inline bool gfs2_iomap_need_write_lock(unsigned flags)
}
static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
unsigned flags, struct iomap *iomap)
unsigned flags, struct iomap *iomap,
struct iomap *srcmap)
{
struct gfs2_inode *ip = GFS2_I(inode);
struct metapath mp = { .mp_aheight = 1, };

25
fs/iomap/apply.c
View File

@ -23,8 +23,10 @@ loff_t
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 iomap = { .type = IOMAP_HOLE };
struct iomap srcmap = { .type = IOMAP_HOLE };
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 != IOMAP_HOLE)
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 != IOMAP_HOLE ? &srcmap : &iomap);
/*
* Now the data has been copied, commit the range we've copied. This

65
fs/iomap/buffered-io.c
View File

@ -234,7 +234,7 @@ 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;
@ -382,7 +382,7 @@ 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;
@ -402,7 +402,7 @@ 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;
@ -582,7 +582,7 @@ 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);
@ -605,7 +605,7 @@ __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);
@ -614,7 +614,7 @@ __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);
@ -624,13 +624,15 @@ __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;
@ -648,13 +650,13 @@ 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;
@ -740,16 +742,16 @@ 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 {
@ -780,7 +782,7 @@ 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;
@ -814,7 +816,8 @@ 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;
@ -825,8 +828,8 @@ 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;
@ -879,7 +882,7 @@ 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;
@ -888,7 +891,7 @@ 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 {
@ -897,11 +900,12 @@ 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;
@ -940,19 +944,19 @@ 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,
@ -964,14 +968,14 @@ 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 {
@ -983,7 +987,8 @@ 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;
@ -1033,7 +1038,7 @@ 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;

2
fs/iomap/direct-io.c
View File

@ -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;

4
fs/iomap/fiemap.c
View File

@ -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;

4
fs/iomap/seek.c
View File

@ -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:

3
fs/iomap/swapfile.c
View File

@ -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;

9
fs/xfs/xfs_iomap.c
View File

@ -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;
@ -1161,7 +1162,8 @@ 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;
@ -1247,7 +1249,8 @@ 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;

5
include/linux/iomap.h
View File

@ -129,7 +129,8 @@ 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.
@ -145,7 +146,7 @@ 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,