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iomap: use write_begin to read pages to unshare 

Use the existing iomap write_begin code to read the pages unshared
by iomap_file_unshare.  That avoids the extra ->readpage call and
extent tree lookup currently done by read_mapping_page.

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>
This commit is contained in:
Christoph Hellwig 2019-10-18 16:42:50 -07:00 committed by Darrick J. Wong
parent d3b4043969
commit 32a38a4991
1 changed files with 16 additions and 33 deletions
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49
fs/iomap/buffered-io.c
View File

@ -548,6 +548,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage,
EXPORT_SYMBOL_GPL(iomap_migrate_page);
#endif /* CONFIG_MIGRATION */
enum {
IOMAP_WRITE_F_UNSHARE = (1 << 0),
};
static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
@ -577,7 +581,7 @@ 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,
__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
struct page *page, struct iomap *iomap)
{
struct iomap_page *iop = iomap_page_create(inode, page);
@ -596,11 +600,14 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
if (plen == 0)
break;
if ((from <= poff || from >= poff + plen) &&
if (!(flags & IOMAP_WRITE_F_UNSHARE) &&
(from <= poff || from >= poff + plen) &&
(to <= poff || to >= poff + plen))
continue;
if (iomap_block_needs_zeroing(inode, iomap, block_start)) {
if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
return -EIO;
zero_user_segments(page, poff, from, to, poff + plen);
iomap_set_range_uptodate(page, poff, plen);
continue;
@ -646,7 +653,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
status = __block_write_begin_int(page, pos, len, NULL, iomap);
else
status = __iomap_write_begin(inode, pos, len, page, iomap);
status = __iomap_write_begin(inode, pos, len, flags, page,
iomap);
if (unlikely(status))
goto out_unlock;
@ -869,22 +877,6 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
static struct page *
__iomap_read_page(struct inode *inode, loff_t offset)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
if (IS_ERR(page))
return page;
if (!PageUptodate(page)) {
put_page(page);
return ERR_PTR(-EIO);
}
return page;
}
static loff_t
iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
struct iomap *iomap)
@ -900,24 +892,15 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
return length;
do {
struct page *page, *rpage;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
unsigned long offset = offset_in_page(pos);
unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
struct page *page;
offset = offset_in_page(pos);
bytes = min_t(loff_t, PAGE_SIZE - offset, length);
rpage = __iomap_read_page(inode, pos);
if (IS_ERR(rpage))
return PTR_ERR(rpage);
status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
put_page(rpage);
status = iomap_write_begin(inode, pos, bytes,
IOMAP_WRITE_F_UNSHARE, &page, iomap);
if (unlikely(status))
return status;
WARN_ON_ONCE(!PageUptodate(page));
status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
if (unlikely(status <= 0)) {
if (WARN_ON_ONCE(status == 0))