[PATCH v14 025/138] mm/writeback: Add folio_wait_writeback()

Matthew Wilcox (Oracle)
2021-07-15T03:58:56Z

wait_on_page_writeback_killable() only has one caller, so convert it to
call folio_wait_writeback_killable(). For the wait_on_page_writeback()
callers, add a compatibility wrapper around folio_wait_writeback().

Turning PageWriteback() into folio_test_writeback() eliminates a call
to compound_head() which saves 8 bytes and 15 bytes in the two
functions. Unfortunately, that is more than offset by adding the
wait_on_page_writeback compatibility wrapper for a net increase in text
of 7 bytes.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
---
fs/afs/write.c | 9 ++++----
include/linux/pagemap.h | 3 ++-
mm/folio-compat.c | 6 ++++++
mm/page-writeback.c | 48 ++++++++++++++++++++++++++++-------------
4 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 3104b62c2082..fb7d5c1cabde 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -839,7 +839,8 @@ int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
*/
vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
{
- struct page *page = thp_head(vmf->page);
+ struct folio *folio = page_folio(vmf->page);
+ struct page *page = &folio->page;
struct file *file = vmf->vma->vm_file;
struct inode *inode = file_inode(file);
struct afs_vnode *vnode = AFS_FS_I(inode);
@@ -859,7 +860,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
goto out;
#endif

- if (wait_on_page_writeback_killable(page))
+ if (folio_wait_writeback_killable(folio))
goto out;

if (lock_page_killable(page) < 0)
@@ -869,8 +870,8 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
* details the portion of the page we need to write back and we might
* need to redirty the page if there's a problem.
*/
- if (wait_on_page_writeback_killable(page) < 0) {
- unlock_page(page);
+ if (folio_wait_writeback_killable(folio) < 0) {
+ folio_unlock(folio);
goto out;
}

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 66a019178550..0c5f53368fe9 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -767,7 +767,8 @@ static inline int wait_on_page_locked_killable(struct page *page)

int put_and_wait_on_page_locked(struct page *page, int state);
void wait_on_page_writeback(struct page *page);
-int wait_on_page_writeback_killable(struct page *page);
+void folio_wait_writeback(struct folio *folio);
+int folio_wait_writeback_killable(struct folio *folio);
void end_page_writeback(struct page *page);
void folio_end_writeback(struct folio *folio);
void wait_for_stable_page(struct page *page);
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 526843d03d58..41275dac7a92 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -23,3 +23,9 @@ void end_page_writeback(struct page *page)
return folio_end_writeback(page_folio(page));
}
EXPORT_SYMBOL(end_page_writeback);
+
+void wait_on_page_writeback(struct page *page)
+{
+ return folio_wait_writeback(page_folio(page));
+}
+EXPORT_SYMBOL_GPL(wait_on_page_writeback);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9f63548f247c..c2c00e1533ad 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2830,33 +2830,51 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
}
EXPORT_SYMBOL(__test_set_page_writeback);

-/*
- * Wait for a page to complete writeback
+/**
+ * folio_wait_writeback - Wait for a folio to finish writeback.
+ * @folio: The folio to wait for.
+ *
+ * If the folio is currently being written back to storage, wait for the
+ * I/O to complete.
+ *
+ * Context: Sleeps. Must be called in process context and with
+ * no spinlocks held. Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
*/
-void wait_on_page_writeback(struct page *page)
+void folio_wait_writeback(struct folio *folio)
{
- while (PageWriteback(page)) {
- trace_wait_on_page_writeback(page, page_mapping(page));
- wait_on_page_bit(page, PG_writeback);
+ while (folio_test_writeback(folio)) {
+ trace_wait_on_page_writeback(&folio->page, folio_mapping(folio));
+ wait_on_page_bit(&folio->page, PG_writeback);
}
}
-EXPORT_SYMBOL_GPL(wait_on_page_writeback);
+EXPORT_SYMBOL_GPL(folio_wait_writeback);

-/*
- * Wait for a page to complete writeback. Returns -EINTR if we get a
- * fatal signal while waiting.
+/**
+ * folio_wait_writeback_killable - Wait for a folio to finish writeback.
+ * @folio: The folio to wait for.
+ *
+ * If the folio is currently being written back to storage, wait for the
+ * I/O to complete or a fatal signal to arrive.
+ *
+ * Context: Sleeps. Must be called in process context and with
+ * no spinlocks held. Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
+ * Return: 0 on success, -EINTR if we get a fatal signal while waiting.
*/
-int wait_on_page_writeback_killable(struct page *page)
+int folio_wait_writeback_killable(struct folio *folio)
{
- while (PageWriteback(page)) {
- trace_wait_on_page_writeback(page, page_mapping(page));
- if (wait_on_page_bit_killable(page, PG_writeback))
+ while (folio_test_writeback(folio)) {
+ trace_wait_on_page_writeback(&folio->page, folio_mapping(folio));
+ if (wait_on_page_bit_killable(&folio->page, PG_writeback))
return -EINTR;
}

return 0;
}
-EXPORT_SYMBOL_GPL(wait_on_page_writeback_killable);
+EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);

/**
* wait_for_stable_page() - wait for writeback to finish, if necessary.
--
2.30.2