linux-kernel - [PATCH v6 25/30] afs: Wait on PG_fscache before modifying/releasing a page

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Message-ID: <161789096241.6155.5907241930823579235.stgit@warthog.procyon.org.uk>
Date:   Thu, 08 Apr 2021 15:09:22 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-afs@...ts.infradead.org, linux-cachefs@...hat.com,
        dhowells@...hat.com,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Jeff Layton <jlayton@...hat.com>,
        David Wysochanski <dwysocha@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-cachefs@...hat.com, 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-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v6 25/30] 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>
cc: linux-afs@...ts.infradead.org
cc: linux-cachefs@...hat.com
cc: linux-fsdevel@...r.kernel.org
Link: https://lore.kernel.org/r/158861253957.340223.7465334678444521655.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/159465832417.1377938.3571599385208729791.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/160588536286.3465195.13231895135369807920.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161118153708.1232039.3535103645871176749.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161161049369.2537118.11591934943429117060.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161340412903.1303470.6424701655031380012.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/161539556890.286939.5873470593519458598.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/161653812726.2770958.18167145829938766503.stgit@warthog.procyon.org.uk/ # v5
---

 fs/afs/file.c  |    9 +++++++++
 fs/afs/write.c |   10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 4a34ffaf6de4..f1e30b89e41c 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -593,6 +593,7 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 	if (PagePrivate(page))
 		afs_invalidate_dirty(page, offset, length);
 
+	wait_on_page_fscache(page);
 	_leave("");
 }
 
@@ -610,6 +611,14 @@ 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)) {
 		detach_page_private(page);
 		trace_afs_page_dirty(vnode, tracepoint_string("rel"), page);
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 6e41b982c71b..1b8cabf5ac92 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -117,6 +117,10 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 		SetPageUptodate(page);
 	}
 
+#ifdef CONFIG_AFS_FSCACHE
+	wait_on_page_fscache(page);
+#endif
+
 try_again:
 	/* See if this page is already partially written in a way that we can
 	 * merge the new write with.
@@ -857,6 +861,11 @@ 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 (wait_on_page_writeback_killable(vmf->page))
 		return VM_FAULT_RETRY;
@@ -947,5 +956,6 @@ int afs_launder_page(struct page *page)
 
 	detach_page_private(page);
 	trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
+	wait_on_page_fscache(page);
 	return ret;
 }