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

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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
Download Patch File Download Diff File Expand all files Collapse all files

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 @@ again:
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 @@ again:
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;