Commit 9a4e7276 authored Apr 09, 2015 by Zhao Lei Committed by Chris Mason Jun 10, 2015

btrfs: wait for delayed iputs on no space



btrfs will report no_space when we run following write and delete
file loop:
 # FILE_SIZE_M=[ 75% of fs space ]
 # DEV=[ some dev ]
 # MNT=[ some dir ]
 #
 # mkfs.btrfs -f "$DEV"
 # mount -o nodatacow "$DEV" "$MNT"
 # for ((i = 0; i < 100; i++)); do dd if=/dev/zero of="$MNT"/file0 bs=1M count="$FILE_SIZE_M"; rm -f "$MNT"/file0; done
 #

Reason:
 iput() and evict() is run after write pages to block device, if
 write pages work is not finished before next write, the "rm"ed space
 is not freed, and caused above bug.

Fix:
 We can add "-o flushoncommit" mount option to avoid above bug, but
 it have performance problem. Actually, we can to wait for on-the-fly
 writes only when no-space happened, it is which this patch do.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent d6726335

fs/btrfs/extent-tree.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -3918,6 +3918,9 @@ commit_trans:
		!atomic_read(&root->fs_info->open_ioctl_trans)) {
		need_commit--;

		if (need_commit > 0)
		btrfs_wait_ordered_roots(fs_info, -1);

		trans = btrfs_join_transaction(root);
		if (IS_ERR(trans))
		return PTR_ERR(trans);

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