mm: Remove the PG_fscache alias for PG_private_2

Remove the PG_fscache alias for PG_private_2 and use the latter directly.
Use of this flag for marking pages undergoing writing to the cache should
be considered deprecated and the folios should be marked dirty instead and
the write done in ->writepages().

Note that PG_private_2 itself should be considered deprecated and up for
future removal by the MM folks too.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Xiubo Li <xiubli@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: Tom Talpey <tom@talpey.com>
cc: Bharath SM <bharathsm@microsoft.com>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Anna Schumaker <anna@kernel.org>
cc: netfs@lists.linux.dev
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

Author: dhowells

fs/ceph/addr.c

@@ -500,7 +500,7 @@ const struct netfs_request_ops ceph_netfs_ops = {
 #ifdef CONFIG_CEPH_FSCACHE
 static void ceph_set_page_fscache(struct page *page)
 {
-	set_page_fscache(page);
+	folio_start_private_2(page_folio(page)); /* [DEPRECATED] */
 }
 
 static void ceph_fscache_write_terminated(void *priv, ssize_t error, bool was_async)
@@ -800,7 +800,7 @@ static int ceph_writepage(struct page *page, struct writeback_control *wbc)
 		return AOP_WRITEPAGE_ACTIVATE;
 	}
 
-	wait_on_page_fscache(page);
+	folio_wait_private_2(page_folio(page)); /* [DEPRECATED] */
 
 	err = writepage_nounlock(page, wbc);
 	if (err == -ERESTARTSYS) {
@@ -1075,15 +1075,16 @@ static int ceph_writepages_start(struct address_space *mapping,
 				unlock_page(page);
 				break;
 			}
-			if (PageWriteback(page) || PageFsCache(page)) {
+			if (PageWriteback(page) ||
+			    PagePrivate2(page) /* [DEPRECATED] */) {
 				if (wbc->sync_mode == WB_SYNC_NONE) {
 					doutc(cl, "%p under writeback\n", page);
 					unlock_page(page);
 					continue;
 				}
 				doutc(cl, "waiting on writeback %p\n", page);
 				wait_on_page_writeback(page);
-				wait_on_page_fscache(page);
+				folio_wait_private_2(page_folio(page)); /* [DEPRECATED] */
 			}
 
 			if (!clear_page_dirty_for_io(page)) {
@@ -1513,7 +1514,7 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
 	if (r < 0)
 		return r;
 
-	folio_wait_fscache(folio);
+	folio_wait_private_2(folio); /* [DEPRECATED] */
 	WARN_ON_ONCE(!folio_test_locked(folio));
 	*pagep = &folio->page;
 	return 0;

fs/netfs/buffered_read.c

@@ -70,7 +70,7 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
 				if (!folio_started && test_bit(NETFS_SREQ_COPY_TO_CACHE,
 							       &subreq->flags)) {
 					trace_netfs_folio(folio, netfs_folio_trace_copy_to_cache);
-					folio_start_fscache(folio);
+					folio_start_private_2(folio);
 					folio_started = true;
 				}
 			} else {
@@ -506,7 +506,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
 
 have_folio:
 	if (test_bit(NETFS_ICTX_USE_PGPRIV2, &ctx->flags)) {
-		ret = folio_wait_fscache_killable(folio);
+		ret = folio_wait_private_2_killable(folio);
 		if (ret < 0)
 			goto error;
 	}

fs/netfs/fscache_io.c

@@ -183,7 +183,7 @@ void __fscache_clear_page_bits(struct address_space *mapping,
 
 		rcu_read_lock();
 		xas_for_each(&xas, page, last) {
-			end_page_fscache(page);
+			folio_end_private_2(page_folio(page));
 		}
 		rcu_read_unlock();
 	}

fs/netfs/io.c

@@ -129,7 +129,7 @@ static void netfs_rreq_unmark_after_write(struct netfs_io_request *rreq,
 				continue;
 			unlocked = folio_next_index(folio) - 1;
 			trace_netfs_folio(folio, netfs_folio_trace_end_copy);
-			folio_end_fscache(folio);
+			folio_end_private_2(folio);
 			have_unlocked = true;
 		}
 	}

fs/nfs/file.c

@@ -433,7 +433,7 @@ static void nfs_invalidate_folio(struct folio *folio, size_t offset,
 		return;
 	/* Cancel any unstarted writes on this page */
 	nfs_wb_folio_cancel(inode, folio);
-	folio_wait_fscache(folio);
+	folio_wait_private_2(folio); /* [DEPRECATED] */
 	trace_nfs_invalidate_folio(inode, folio);
 }
 
@@ -500,7 +500,7 @@ static int nfs_launder_folio(struct folio *folio)
 	dfprintk(PAGECACHE, "NFS: launder_folio(%ld, %llu)\n",
 		inode->i_ino, folio_pos(folio));
 
-	folio_wait_fscache(folio);
+	folio_wait_private_2(folio); /* [DEPRECATED] */
 	ret = nfs_wb_folio(inode, folio);
 	trace_nfs_launder_folio_done(inode, folio, ret);
 	return ret;
@@ -593,8 +593,8 @@ static vm_fault_t nfs_vm_page_mkwrite(struct vm_fault *vmf)
 	sb_start_pagefault(inode->i_sb);
 
 	/* make sure the cache has finished storing the page */
-	if (folio_test_fscache(folio) &&
-	    folio_wait_fscache_killable(folio) < 0) {
+	if (folio_test_private_2(folio) && /* [DEPRECATED] */
+	    folio_wait_private_2_killable(folio) < 0) {
 		ret = VM_FAULT_RETRY;
 		goto out;
 	}

fs/nfs/fscache.h

@@ -103,10 +103,10 @@ extern int nfs_netfs_read_folio(struct file *file, struct folio *folio);
 
 static inline bool nfs_fscache_release_folio(struct folio *folio, gfp_t gfp)
 {
-	if (folio_test_fscache(folio)) {
+	if (folio_test_private_2(folio)) { /* [DEPRECATED] */
 		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return false;
-		folio_wait_fscache(folio);
+		folio_wait_private_2(folio);
 	}
 	fscache_note_page_release(netfs_i_cookie(netfs_inode(folio->mapping->host)));
 	return true;

fs/nfs/write.c

@@ -2120,10 +2120,10 @@ int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
 	if (folio_test_private(src))
 		return -EBUSY;
 
-	if (folio_test_fscache(src)) {
+	if (folio_test_private_2(src)) { /* [DEPRECATED] */
 		if (mode == MIGRATE_ASYNC)
 			return -EBUSY;
-		folio_wait_fscache(src);
+		folio_wait_private_2(src);
 	}
 
 	return migrate_folio(mapping, dst, src, mode);

fs/smb/client/file.c

@@ -3032,12 +3032,12 @@ static ssize_t cifs_writepages_begin(struct address_space *mapping,
 	}
 
 	if (folio_test_writeback(folio) ||
-	    folio_test_fscache(folio)) {
+	    folio_test_private_2(folio)) { /* [DEPRECATED] */
 		folio_unlock(folio);
 		if (wbc->sync_mode != WB_SYNC_NONE) {
 			folio_wait_writeback(folio);
 #ifdef CONFIG_CIFS_FSCACHE
-			folio_wait_fscache(folio);
+			folio_wait_private_2(folio);
 #endif
 			goto lock_again;
 		}
@@ -4510,8 +4510,8 @@ static vm_fault_t cifs_page_mkwrite(struct vm_fault *vmf)
 	 * be modified.  We then assume the entire folio will need writing back.
 	 */
 #ifdef CONFIG_CIFS_FSCACHE
-	if (folio_test_fscache(folio) &&
-	    folio_wait_fscache_killable(folio) < 0)
+	if (folio_test_private_2(folio) && /* [DEPRECATED] */
+	    folio_wait_private_2_killable(folio) < 0)
 		return VM_FAULT_RETRY;
 #endif
 
@@ -4977,10 +4977,10 @@ static bool cifs_release_folio(struct folio *folio, gfp_t gfp)
 {
 	if (folio_test_private(folio))
 		return 0;
-	if (folio_test_fscache(folio)) {
+	if (folio_test_private_2(folio)) { /* [DEPRECATED] */
 		if (current_is_kswapd() || !(gfp & __GFP_FS))
 			return false;
-		folio_wait_fscache(folio);
+		folio_wait_private_2(folio);
 	}
 	fscache_note_page_release(cifs_inode_cookie(folio->mapping->host));
 	return true;
@@ -4989,7 +4989,7 @@ static bool cifs_release_folio(struct folio *folio, gfp_t gfp)
 static void cifs_invalidate_folio(struct folio *folio, size_t offset,
 				 size_t length)
 {
-	folio_wait_fscache(folio);
+	folio_wait_private_2(folio); /* [DEPRECATED] */
 }
 
 static int cifs_launder_folio(struct folio *folio)
@@ -5009,7 +5009,7 @@ static int cifs_launder_folio(struct folio *folio)
 	if (folio_clear_dirty_for_io(folio))
 		rc = cifs_writepage_locked(&folio->page, &wbc);
 
-	folio_wait_fscache(folio);
+	folio_wait_private_2(folio); /* [DEPRECATED] */
 	return rc;
 }
 

include/linux/netfs.h

@@ -21,94 +21,22 @@
 
 enum netfs_sreq_ref_trace;
 
-/*
- * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
- * a page is currently backed by a local disk cache
- */
-#define folio_test_fscache(folio)	folio_test_private_2(folio)
-#define PageFsCache(page)		PagePrivate2((page))
-#define SetPageFsCache(page)		SetPagePrivate2((page))
-#define ClearPageFsCache(page)		ClearPagePrivate2((page))
-#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
-#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
-
 /**
- * folio_start_fscache - Start an fscache write on a folio.
+ * folio_start_private_2 - Start an fscache write on a folio.  [DEPRECATED]
  * @folio: The folio.
  *
  * Call this function before writing a folio to a local cache.  Starting a
  * second write before the first one finishes is not allowed.
+ *
+ * Note that this should no longer be used.
  */
-static inline void folio_start_fscache(struct folio *folio)
+static inline void folio_start_private_2(struct folio *folio)
 {
 	VM_BUG_ON_FOLIO(folio_test_private_2(folio), folio);
 	folio_get(folio);
 	folio_set_private_2(folio);
 }
 
-/**
- * folio_end_fscache - End an fscache write on a folio.
- * @folio: The folio.
- *
- * Call this function after the folio has been written to the local cache.
- * This will wake any sleepers waiting on this folio.
- */
-static inline void folio_end_fscache(struct folio *folio)
-{
-	folio_end_private_2(folio);
-}
-
-/**
- * folio_wait_fscache - Wait for an fscache write on this folio to end.
- * @folio: The folio.
- *
- * If this folio is currently being written to a local cache, wait for
- * the write to finish.  Another write may start after this one finishes,
- * unless the caller holds the folio lock.
- */
-static inline void folio_wait_fscache(struct folio *folio)
-{
-	folio_wait_private_2(folio);
-}
-
-/**
- * folio_wait_fscache_killable - Wait for an fscache write on this folio to end.
- * @folio: The folio.
- *
- * If this folio is currently being written to a local cache, wait
- * for the write to finish or for a fatal signal to be received.
- * Another write may start after this one finishes, unless the caller
- * holds the folio lock.
- *
- * Return:
- * - 0 if successful.
- * - -EINTR if a fatal signal was encountered.
- */
-static inline int folio_wait_fscache_killable(struct folio *folio)
-{
-	return folio_wait_private_2_killable(folio);
-}
-
-static inline void set_page_fscache(struct page *page)
-{
-	folio_start_fscache(page_folio(page));
-}
-
-static inline void end_page_fscache(struct page *page)
-{
-	folio_end_private_2(page_folio(page));
-}
-
-static inline void wait_on_page_fscache(struct page *page)
-{
-	folio_wait_private_2(page_folio(page));
-}
-
-static inline int wait_on_page_fscache_killable(struct page *page)
-{
-	return folio_wait_private_2_killable(page_folio(page));
-}
-
 /* Marks used on xarray-based buffers */
 #define NETFS_BUF_PUT_MARK	XA_MARK_0	/* - Page needs putting  */
 #define NETFS_BUF_PAGECACHE_MARK XA_MARK_1	/* - Page needs wb/dirty flag wrangling */

mm/filemap.c

@@ -1540,7 +1540,7 @@ EXPORT_SYMBOL(folio_end_private_2);
  * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
  * @folio: The folio to wait on.
  *
- * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
+ * Wait for PG_private_2 to be cleared on a folio.
  */
 void folio_wait_private_2(struct folio *folio)
 {
@@ -1553,8 +1553,8 @@ EXPORT_SYMBOL(folio_wait_private_2);
  * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
  * @folio: The folio to wait on.
  *
- * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
- * fatal signal is received by the calling task.
+ * Wait for PG_private_2 to be cleared on a folio or until a fatal signal is
+ * received by the calling task.
  *
  * Return:
  * - 0 if successful.