From: NeilBrown <neilb@suse.de>
Date: Sun, 1 Aug 2010 00:57:01 +0000 (+1000)
Subject: wait more effectively for truncate to progress.
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=8c394fff184ed83cbc4ac3c48c99440fdc7d4b02;p=LaFS.git

wait more effectively for truncate to progress.

The times that we wait for truncate to progress, we hold
i_mutex, so truncate cannot progress.
So if there is a need to wait, we need to call the orphan
handler directly.

Signed-off-by: NeilBrown <neilb@suse.de>
---

diff --git a/file.c b/file.c
index 9c940a1..437be73 100644
--- a/file.c
+++ b/file.c
@@ -137,6 +137,7 @@ lafs_write_begin(struct file *file, struct address_space *mapping,
 	pgoff_t index;
 	unsigned from, to;
 	struct page *page;
+	DEFINE_WAIT(wq);
 
 	index = pos >> PAGE_CACHE_SHIFT;
 	from = pos & (PAGE_CACHE_SIZE - 1);
@@ -145,9 +146,18 @@ lafs_write_begin(struct file *file, struct address_space *mapping,
 	first = from >> bits;
 	last = (to-1) >> bits;
 
-	wait_event(fs->trunc_wait,
-		   !test_bit(I_Trunc, &LAFSI(ino)->iflags) ||
-		   LAFSI(ino)->trunc_next > last);
+	while (test_bit(I_Trunc, &LAFSI(ino)->iflags) &&
+	       LAFSI(ino)->trunc_next <= last) {
+		struct datablock *db = lafs_inode_dblock(ino,
+							 SYNC, MKREF(writetrunc));
+		prepare_to_wait(&fs->async_complete, &wq,
+				TASK_UNINTERRUPTIBLE);
+		lafs_inode_handle_orphan(db);
+		if (test_bit(B_Orphan, &db->b.flags))
+			schedule();
+		putdref(db, MKREF(writetrunc));
+	}
+	finish_wait(&fs->async_complete, &wq);
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,29)
 	page = __grab_cache_page(mapping, index);
diff --git a/inode.c b/inode.c
index 52f5d99..9ca882e 100644
--- a/inode.c
+++ b/inode.c
@@ -1591,20 +1591,31 @@ void lafs_truncate(struct inode *ino)
 	 */
 	struct fs *fs = fs_from_inode(ino);
 	struct datablock *db = lafs_inode_dblock(ino, SYNC, MKREF(trunc));
+	loff_t trunc_block;
+	DEFINE_WAIT(wq);
 
 	if (IS_ERR(db))
 		return;
 
-	wait_event(fs->trunc_wait,
-		   !test_bit(I_Trunc, &LAFSI(ino)->iflags));
+	trunc_block = ((i_size_read(ino) + fs->blocksize - 1)
+		       >> fs->blocksize_bits);
+	/* We hold i_mutex, so regular orphan processing cannot
+	 * contine - we have to push it forward ourselves.
+	 */
+	while (test_bit(I_Trunc, &LAFSI(ino)->iflags) &&
+	       LAFSI(ino)->trunc_next < trunc_block) {
+		prepare_to_wait(&fs->async_complete, &wq,
+				TASK_UNINTERRUPTIBLE);
+		lafs_inode_handle_orphan(db);
+		if (test_bit(B_Orphan, &db->b.flags))
+			schedule();
+	}
+	finish_wait(&fs->async_complete, &wq);
 
 	/* FIXME there is nothing I can do with an error here */
 	lafs_make_orphan(fs, db);
 
-	LAFSI(ino)->trunc_next = (i_size_read(ino) +
-				  fs->blocksize - 1)
-		>> fs->blocksize_bits;
-	set_bit(I_Trunc, &LAFSI(ino)->iflags);
+	LAFSI(ino)->trunc_next = trunc_block;
 	putdref(db, MKREF(trunc));
 }