Re: [PATCH 1/2] mm: move filemap_range_needs_writeback() into header

[Jens Axboe <axboe@kernel.dk>]

On 12/3/21 10:57 AM, Jens Axboe wrote:
>> I'm happy with this, if you just move it to pagemap.h
> 
> OK, I'll try it out.

Wasn't too bad at all, actually just highlighted that I missed removing
the previous declaration of filemap_range_needs_writeback() in fs.h
I'll do a full compile and test, but this seems sane.

commit 63c6b3846b77041d239d5b5b5a907b5c82a21c4c
Author: Jens Axboe <axboe@kernel.dk>
Date:   Thu Oct 28 08:47:05 2021 -0600

    mm: move filemap_range_needs_writeback() into header
    
    No functional changes in this patch, just in preparation for efficiently
    calling this light function from the block O_DIRECT handling.
    
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bbf812ce89a8..6b8dc1a78df6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2847,8 +2847,6 @@ static inline int filemap_fdatawait(struct address_space *mapping)
 
 extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
 				  loff_t lend);
-extern bool filemap_range_needs_writeback(struct address_space *,
-					  loff_t lstart, loff_t lend);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
 				        loff_t lstart, loff_t lend);
 extern int __filemap_fdatawrite_range(struct address_space *mapping,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 605246452305..274a0710f2c5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -963,6 +963,35 @@ static inline int add_to_page_cache(struct page *page,
 int __filemap_add_folio(struct address_space *mapping, struct folio *folio,
 		pgoff_t index, gfp_t gfp, void **shadowp);
 
+bool filemap_range_has_writeback(struct address_space *mapping,
+				 loff_t start_byte, loff_t end_byte);
+
+/**
+ * filemap_range_needs_writeback - check if range potentially needs writeback
+ * @mapping:           address space within which to check
+ * @start_byte:        offset in bytes where the range starts
+ * @end_byte:          offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback. Used by O_DIRECT
+ * read/write with IOCB_NOWAIT, to see if the caller needs to do
+ * filemap_write_and_wait_range() before proceeding.
+ *
+ * Return: %true if the caller should do filemap_write_and_wait_range() before
+ * doing O_DIRECT to a page in this range, %false otherwise.
+ */
+static inline bool filemap_range_needs_writeback(struct address_space *mapping,
+						 loff_t start_byte,
+						 loff_t end_byte)
+{
+	if (!mapping->nrpages)
+		return false;
+	if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
+	    !mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
+		return false;
+	return filemap_range_has_writeback(mapping, start_byte, end_byte);
+}
+
 /**
  * struct readahead_control - Describes a readahead request.
  *
diff --git a/mm/filemap.c b/mm/filemap.c
index daa0e23a6ee6..655c9eec06b3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -646,8 +646,8 @@ static bool mapping_needs_writeback(struct address_space *mapping)
 	return mapping->nrpages;
 }
 
-static bool filemap_range_has_writeback(struct address_space *mapping,
-					loff_t start_byte, loff_t end_byte)
+bool filemap_range_has_writeback(struct address_space *mapping,
+				 loff_t start_byte, loff_t end_byte)
 {
 	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
 	pgoff_t max = end_byte >> PAGE_SHIFT;
@@ -667,34 +667,8 @@ static bool filemap_range_has_writeback(struct address_space *mapping,
 	}
 	rcu_read_unlock();
 	return page != NULL;
-
-}
-
-/**
- * filemap_range_needs_writeback - check if range potentially needs writeback
- * @mapping:           address space within which to check
- * @start_byte:        offset in bytes where the range starts
- * @end_byte:          offset in bytes where the range ends (inclusive)
- *
- * Find at least one page in the range supplied, usually used to check if
- * direct writing in this range will trigger a writeback. Used by O_DIRECT
- * read/write with IOCB_NOWAIT, to see if the caller needs to do
- * filemap_write_and_wait_range() before proceeding.
- *
- * Return: %true if the caller should do filemap_write_and_wait_range() before
- * doing O_DIRECT to a page in this range, %false otherwise.
- */
-bool filemap_range_needs_writeback(struct address_space *mapping,
-				   loff_t start_byte, loff_t end_byte)
-{
-	if (!mapping_needs_writeback(mapping))
-		return false;
-	if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
-	    !mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
-		return false;
-	return filemap_range_has_writeback(mapping, start_byte, end_byte);
 }
-EXPORT_SYMBOL_GPL(filemap_range_needs_writeback);
+EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
 
 /**
  * filemap_write_and_wait_range - write out & wait on a file range

-- 
Jens Axboe