From 32a38a4991043976fc2d8840a55ce5dde41fdbd0 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 18 Oct 2019 16:42:50 -0700 Subject: [PATCH] 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 Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/iomap/buffered-io.c | 49 ++++++++++++++---------------------------- 1 file changed, 16 insertions(+), 33 deletions(-) diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 7e9d7fdaae49..b61076823544 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -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))