[PATCH][CIFS] writeback fix

[Steve French <smfrench@xxxxxxxxx>]

https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=d9a5f40a52016abe765d97d1e57acead9e824a12

   Wait for the page to be written to the cache before we allow it
    to be modified

    Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
    Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index a2723f7cb5e9..cf8642c16e59 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4210,13 +4210,19 @@ cifs_page_mkwrite(struct vm_fault *vmf)
 {
        struct page *page = vmf->page;

+       /* Wait for the page to be written to the cache before we allow it to
+        * be modified.  We then assume the entire page will need writing back.
+        */
 #ifdef CONFIG_CIFS_FSCACHE
        if (PageFsCache(page) &&
            wait_on_page_fscache_killable(page) < 0)
                return VM_FAULT_RETRY;
 #endif

-       lock_page(page);
+       wait_on_page_writeback(page);
+
+       if (lock_page_killable(page) < 0)
+               return VM_FAULT_RETRY;
        return VM_FAULT_LOCKED;
 }

-- 
Thanks,

Steve

From d9a5f40a52016abe765d97d1e57acead9e824a12 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@xxxxxxxxxx>
Date: Mon, 24 Jan 2022 23:15:18 +0000
Subject: [PATCH] cifs: writeback fix

Wait for the page to be written to the cache before we allow it
to be modified

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
---
 fs/cifs/file.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index a2723f7cb5e9..cf8642c16e59 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4210,13 +4210,19 @@ cifs_page_mkwrite(struct vm_fault *vmf)
 {
 	struct page *page = vmf->page;
 
+	/* Wait for the page to be written to the cache before we allow it to
+	 * be modified.  We then assume the entire page will need writing back.
+	 */
 #ifdef CONFIG_CIFS_FSCACHE
 	if (PageFsCache(page) &&
 	    wait_on_page_fscache_killable(page) < 0)
 		return VM_FAULT_RETRY;
 #endif
 
-	lock_page(page);
+	wait_on_page_writeback(page);
+
+	if (lock_page_killable(page) < 0)
+		return VM_FAULT_RETRY;
 	return VM_FAULT_LOCKED;
 }
 
-- 
2.32.0