iomap: Simplify iomap_do_writepage()

Rename end_offset to end_pos and offset_into_page to poff to match the
rest of the file.  Simplify the handling of the last page straddling
i_size by doing the EOF check based on the byte granularity i_size
instead of converting to a pgoff prematurely.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 18c4498dab42059c2a5b816d4ef8c48401d56eb9..9aebe1521630c9bfa06da82c7d5dfab7fc4224ca 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1405,9 +1405,7 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
 {
        struct iomap_writepage_ctx *wpc = data;
        struct inode *inode = page->mapping->host;
-       pgoff_t end_index;
-       u64 end_offset;
-       loff_t offset;
+       u64 end_pos, isize;
 
        trace_iomap_writepage(inode, page_offset(page), PAGE_SIZE);
 
@@ -1438,11 +1436,9 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
         * |     desired writeback range    |      see else    |
         * ---------------------------------^------------------|
         */
-       offset = i_size_read(inode);
-       end_index = offset >> PAGE_SHIFT;
-       if (page->index < end_index)
-               end_offset = (loff_t)(page->index + 1) << PAGE_SHIFT;
-       else {
+       isize = i_size_read(inode);
+       end_pos = page_offset(page) + PAGE_SIZE;
+       if (end_pos > isize) {
                /*
                 * Check whether the page to write out is beyond or straddles
                 * i_size or not.
@@ -1454,7 +1450,8 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
                 * |                                |      Straddles     |
                 * ---------------------------------^-----------|--------|
                 */
-               unsigned offset_into_page = offset & (PAGE_SIZE - 1);
+               size_t poff = offset_in_page(isize);
+               pgoff_t end_index = isize >> PAGE_SHIFT;
 
                /*
                 * Skip the page if it's fully outside i_size, e.g. due to a
@@ -1474,7 +1471,7 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
                 * offset is just equal to the EOF.
                 */
                if (page->index > end_index ||
-                   (page->index == end_index && offset_into_page == 0))
+                   (page->index == end_index && poff == 0))
                        goto redirty;
 
                /*
@@ -1485,13 +1482,13 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
                 * memory is zeroed when mapped, and writes to that region are
                 * not written out to the file."
                 */
-               zero_user_segment(page, offset_into_page, PAGE_SIZE);
+               zero_user_segment(page, poff, PAGE_SIZE);
 
                /* Adjust the end_offset to the end of file */
-               end_offset = offset;
+               end_pos = isize;
        }
 
-       return iomap_writepage_map(wpc, wbc, inode, page, end_offset);
+       return iomap_writepage_map(wpc, wbc, inode, page, end_pos);
 
 redirty:
        redirty_page_for_writepage(wbc, page);