From 47279570a1fd14b1fbd75f020ae151d5ef20a7c4 Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@zip.com.au>
Date: Mon, 27 May 2002 05:12:22 -0700
Subject: [PATCH] [PATCH] relax nr_to_write requirements

Relax the requirements on the writeback_mapping a_op.

This function is passed the number of pages which it should write.  The
current fs-writeback.c code will get confused if the address_space
writes back more pages than it was asked to.

With this change the address_space may write more pages than required
if that is convenient.  Extent-based fileystems may wish to do this.
---
 Documentation/filesystems/Locking | 11 ++++++-----
 fs/fs-writeback.c                 |  4 ++--
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index cb0263288366..aff3575d2828 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -179,11 +179,12 @@ existing instances of this method ->sync_page() itself doesn't look
 well-defined...
 
 	->writeback_mapping() is used for periodic writeback and for
-systemcall-initiated sync operations. The address_space should start
-I/O against at least *nr_to_write pages.  *nr_to_write must be decremented
-for each page which is written.  *nr_to_write must not go negative (this
-will be relaxed later).  If nr_to_write is NULL, all dirty pages must
-be written.
+systemcall-initiated sync operations.  The address_space should start
+I/O against at least *nr_to_write pages.  *nr_to_write must be
+decremented for each page which is written.  The address_space
+implementation may write more (or less) pages than *nr_to_write asks
+for, but it should try to be reasonably close.  If nr_to_write is NULL,
+all dirty pages must be written.
 
 	->vm_writeback() is called from the VM.  The address_space should
 start I/O against at least *nr_to_write pages, including the passed page. As
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 348b7bf6b8c0..c16577f9001d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -257,7 +257,7 @@ static void sync_sb_inodes(struct super_block *sb, int sync_mode,
 		if (current_is_pdflush())
 			writeback_release(bdi);
 
-		if (nr_to_write && *nr_to_write == 0)
+		if (nr_to_write && *nr_to_write <= 0)
 			break;
 	}
 out:
@@ -301,7 +301,7 @@ void writeback_unlocked_inodes(int *nr_to_write, int sync_mode,
 					older_than_this);
 			spin_lock(&sb_lock);
 		}
-		if (nr_to_write && *nr_to_write == 0)
+		if (nr_to_write && *nr_to_write <= 0)
 			break;
 	}
 	spin_unlock(&sb_lock);
-- 
2.30.9