linux-kernel - [RFC PATCH 54/61] afs: Wait on PG_fscache before modifying/releasing a page

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Date:   Mon, 04 May 2020 18:15:39 +0100
From:   David Howells <dhowells@...hat.com>
To:     Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Jeff Layton <jlayton@...hat.com>
Cc:     dhowells@...hat.com, Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 54/61] afs: Wait on PG_fscache before modifying/releasing
 a page

PG_fscache is going to be used to indicate that a page is being written to
the cache, and that the page should not be modified or released until it's
finished.

Make afs_invalidatepage() and afs_releasepage() wait for it.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/file.c  |   13 +++++++++++++
 fs/afs/write.c |    9 +++++++++
 2 files changed, 22 insertions(+)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index ea9f6d45d9ff..b25c5ab1f4e1 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -548,6 +548,11 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 
 	/* we clean up only if the entire page is being invalidated */
 	if (offset == 0 && length == PAGE_SIZE) {
+#ifdef CONFIG_AFS_FSCACHE
+		if (PageFsCache(page))
+			wait_on_page_fscache(page);
+#endif
+
 		if (PagePrivate(page)) {
 			priv = page_private(page);
 			trace_afs_page_dirty(vnode, tracepoint_string("inval"),
@@ -575,6 +580,14 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 
 	/* deny if page is being written to the cache and the caller hasn't
 	 * elected to wait */
+#ifdef CONFIG_AFS_FSCACHE
+	if (PageFsCache(page)) {
+		if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
+			return false;
+		wait_on_page_fscache(page);
+	}
+#endif
+
 	if (PagePrivate(page)) {
 		priv = page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("rel"),
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 390fee44446c..3632909fcd91 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -111,6 +111,10 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 		SetPageUptodate(page);
 	}
 
+#ifdef CONFIG_AFS_FSCACHE
+	wait_on_page_fscache(page);
+#endif
+
 	/* page won't leak in error case: it eventually gets cleaned off LRU */
 	*pagep = page;
 
@@ -786,6 +790,11 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 	/* 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_AFS_FSCACHE
+	if (PageFsCache(vmf->page) &&
+	    wait_on_page_bit_killable(vmf->page, PG_fscache) < 0)
+		return VM_FAULT_RETRY;
+#endif
 
 	if (PageWriteback(vmf->page) &&
 	    wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)