From: Christoph Hellwig <hch@lst.de>

BugLink: http://bugs.launchpad.net/bugs/585092

commit cf37e972478ec58a8a54a6b4f951815f0ae28f78 upstream

Make sure that not only sync_filesystem but all callers of writeback_inodes_sb
have the superblock protected against remount. As-is this disables all
functionality for these callers, but the next patch relies on this locking to
fix writeback_inodes_sb for sync_filesystem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
---
fs/fs-writeback.c | 6 ++++++
fs/ubifs/budget.c | 2 ++
2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 3a1afb3..7f91e6f 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1162,6 +1162,8 @@ void writeback_inodes_sb(struct super_block *sb)
.sync_mode = WB_SYNC_NONE,
};

+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
args.nr_pages = nr_dirty + nr_unstable +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);

@@ -1179,7 +1181,9 @@ EXPORT_SYMBOL(writeback_inodes_sb);
int writeback_inodes_sb_if_idle(struct super_block *sb)
{
if (!writeback_in_progress(sb->s_bdi)) {
+ down_read(&sb->s_umount);
writeback_inodes_sb(sb);
+ up_read(&sb->s_umount);
return 1;
} else
return 0;
@@ -1202,6 +1206,8 @@ void sync_inodes_sb(struct super_block *sb)
.range_cyclic = 0,
};

+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
bdi_queue_work_onstack(&args);
wait_sb_inodes(sb);
}
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index 076ca50..c8ff0d1 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -62,7 +62,9 @@
*/
static void shrink_liability(struct ubifs_info *c, int nr_to_write)
{
+ down_read(&c->vfs_sb->s_umount);
writeback_inodes_sb(c->vfs_sb);
+ up_read(&c->vfs_sb->s_umount);
}

/**
--
1.7.0.4


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