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From: David Howells <dhowells@redhat.com>
To: Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@lst.de>,
	linux-mm@kvack.org, linux-cachefs@redhat.com,
	linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
	v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, dhowells@redhat.com,
	Jeff Layton <jlayton@redhat.com>,
	David Wysochanski <dwysocha@redhat.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v5 03/28] mm: Add set/end/wait functions for PG_private_2
Date: Tue, 23 Mar 2021 22:18:02 +0000	[thread overview]
Message-ID: <161653788200.2770958.9517755716374927208.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <161653784755.2770958.11820491619308713741.stgit@warthog.procyon.org.uk>

Add three functions to manipulate PG_private_2:

 (*) set_page_private_2() - Set the flag and take an appropriate reference
     on the flagged page.

 (*) end_page_private_2() - Clear the flag, drop the reference and wake up
     any waiters, somewhat analogously with end_page_writeback().

 (*) wait_on_page_private_2() - Wait for the flag to be cleared.

Wrappers will need to be placed in the netfs lib header in the patch that
adds that.

[This implements a suggestion by Linus[1] to not mix the terminology of
 PG_private_2 and PG_fscache in the mm core function]

Changes:
v5:
- Add set and end functions, calling the end function end rather than
  unlock[3].
- Keep a ref on the page when PG_private_2 is set[4][5].

v4:
- Remove extern from the declaration[2].

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christoph Hellwig <hch@lst.de>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: v9fs-developer@lists.sourceforge.net
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/1330473.1612974547@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/CAHk-=wjgA-74ddehziVk=XAEMTKswPu1Yw4uaro1R3ibs27ztw@mail.gmail.com/ [1]
Link: https://lore.kernel.org/r/20210216102659.GA27714@lst.de/ [2]
Link: https://lore.kernel.org/r/161340387944.1303470.7944159520278177652.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/161539528910.286939.1252328699383291173.stgit@warthog.procyon.org.uk # v4
Link: https://lore.kernel.org/r/20210321105309.GG3420@casper.infradead.org [3]
Link: https://lore.kernel.org/r/CAHk-=wh+2gbF7XEjYc=HV9w_2uVzVf7vs60BPz0gFA=+pUm3ww@mail.gmail.com/ [4]
Link: https://lore.kernel.org/r/CAHk-=wjSGsRj7xwhSMQ6dAQiz53xA39pOG+XA_WeTgwBBu4uqg@mail.gmail.com/ [5]
---

 include/linux/pagemap.h |   19 +++++++++++++++
 mm/filemap.c            |   59 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 444155ae56c0..da5c38864037 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -689,6 +689,25 @@ void wait_for_stable_page(struct page *page);
 
 void page_endio(struct page *page, bool is_write, int err);
 
+/**
+ * set_page_private_2 - Set PG_private_2 on a page and take a ref
+ * @page: The page.
+ *
+ * Set the PG_private_2 flag on a page and take the reference needed for the VM
+ * to handle its lifetime correctly.  This sets the flag and takes the
+ * reference unconditionally, so care must be taken not to set the flag again
+ * if it's already set.
+ */
+static inline void set_page_private_2(struct page *page)
+{
+	get_page(page);
+	SetPagePrivate2(page);
+}
+
+void end_page_private_2(struct page *page);
+void wait_on_page_private_2(struct page *page);
+int wait_on_page_private_2_killable(struct page *page);
+
 /*
  * Add an arbitrary waiter to a page's wait queue
  */
diff --git a/mm/filemap.c b/mm/filemap.c
index 43700480d897..788b71e8a72d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1432,6 +1432,65 @@ void unlock_page(struct page *page)
 }
 EXPORT_SYMBOL(unlock_page);
 
+/**
+ * end_page_private_2 - Clear PG_private_2 and release any waiters
+ * @page: The page
+ *
+ * Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
+ * this.  The page ref held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+void end_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	VM_BUG_ON_PAGE(!PagePrivate2(page), page);
+	clear_bit_unlock(PG_private_2, &page->flags);
+	wake_up_page_bit(page, PG_private_2);
+	put_page(page);
+}
+EXPORT_SYMBOL(end_page_private_2);
+
+/**
+ * wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
+ */
+void wait_on_page_private_2(struct page *page)
+{
+	while (PagePrivate2(page))
+		wait_on_page_bit(page, PG_private_2);
+}
+EXPORT_SYMBOL(wait_on_page_private_2);
+
+/**
+ * wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+int wait_on_page_private_2_killable(struct page *page)
+{
+	int ret = 0;
+
+	while (PagePrivate2(page)) {
+		ret = wait_on_page_bit_killable(page, PG_private_2);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(wait_on_page_private_2_killable);
+
 /**
  * end_page_writeback - end writeback against a page
  * @page: the page



  parent reply	other threads:[~2021-03-23 22:19 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-23 22:17 [PATCH v5 00/28] Network fs helper library & fscache kiocb API David Howells
2021-03-23 22:17 ` [PATCH v5 01/28] iov_iter: Add ITER_XARRAY David Howells
2021-03-23 22:17 ` [PATCH v5 02/28] mm: Add wait_on_page_writeback_killable() David Howells
2021-03-23 22:18 ` David Howells [this message]
2021-03-23 22:18 ` [PATCH v5 04/28] mm: Implement readahead_control pageset expansion David Howells
2021-03-23 22:18 ` [PATCH v5 05/28] netfs: Make a netfs helper module David Howells
2021-03-23 22:18 ` [PATCH v5 06/28] netfs: Documentation for helper library David Howells
2021-03-23 22:18 ` [PATCH v5 07/28] netfs, mm: Move PG_fscache helper funcs to linux/netfs.h David Howells
2021-03-23 22:18 ` [PATCH v5 08/28] netfs, mm: Add set/end/wait_on_page_fscache() aliases David Howells
2021-03-23 22:19 ` [PATCH v5 09/28] netfs: Provide readahead and readpage netfs helpers David Howells
2021-03-23 22:19 ` [PATCH v5 10/28] netfs: Add tracepoints David Howells
2021-03-23 22:19 ` [PATCH v5 11/28] netfs: Gather stats David Howells
2021-03-23 22:19 ` [PATCH v5 12/28] netfs: Add write_begin helper David Howells
2021-03-23 22:19 ` [PATCH v5 13/28] netfs: Define an interface to talk to a cache David Howells
2021-03-23 22:20 ` [PATCH v5 14/28] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache David Howells
2021-03-23 22:20 ` [PATCH v5 15/28] afs: Disable use of the fscache I/O routines David Howells
2021-03-23 22:20 ` [PATCH v5 16/28] afs: Pass page into dirty region helpers to provide THP size David Howells
2021-03-23 22:20 ` [PATCH v5 17/28] afs: Print the operation debug_id when logging an unexpected data version David Howells
2021-03-23 22:21 ` [PATCH v5 18/28] afs: Move key to afs_read struct David Howells
2021-03-23 22:21 ` [PATCH v5 19/28] afs: Don't truncate iter during data fetch David Howells
2021-03-23 22:21 ` [PATCH v5 20/28] afs: Log remote unmarshalling errors David Howells
2021-03-23 22:21 ` [PATCH v5 21/28] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2021-03-23 22:21 ` [PATCH v5 22/28] afs: Use ITER_XARRAY for writing David Howells
2021-03-23 22:22 ` [PATCH v5 23/28] afs: Wait on PG_fscache before modifying/releasing a page David Howells
2021-03-23 22:22 ` [PATCH v5 24/28] afs: Extract writeback extension into its own function David Howells
2021-03-23 22:22 ` [PATCH v5 25/28] afs: Prepare for use of THPs David Howells
2021-03-23 22:22 ` [PATCH v5 26/28] afs: Use the fs operation ops to handle FetchData completion David Howells
2021-03-23 22:22 ` [PATCH v5 27/28] afs: Use new fscache read helper API David Howells
2021-03-23 22:23 ` [PATCH v5 28/28] afs: Use the fscache_write_begin() helper David Howells

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