From b1f382178d150f256c1cf95b9341fda6eb764459 Mon Sep 17 00:00:00 2001
From: Ross Zwisler <zwisler@kernel.org>
Date: Tue, 11 Sep 2018 13:31:16 -0400
Subject: [PATCH] ext4: close race between direct IO and ext4_break_layouts()
Git-commit: b1f382178d150f256c1cf95b9341fda6eb764459
Patch-mainline: v4.19-rc5
References: bsc#1104888
If the refcount of a page is lowered between the time that it is returned
by dax_busy_page() and when the refcount is again checked in
ext4_break_layouts() => ___wait_var_event(), the waiting function
ext4_wait_dax_page() will never be called. This means that
ext4_break_layouts() will still have 'retry' set to false, so we'll stop
looping and never check the refcount of other pages in this inode.
Instead, always continue looping as long as dax_layout_busy_page() gives us
a page which it found with an elevated refcount.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Acked-by: Jan Kara <jack@suse.cz>
---
fs/ext4/inode.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 694f31364206..723058bfe43b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4195,9 +4195,8 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
return 0;
}
-static void ext4_wait_dax_page(struct ext4_inode_info *ei, bool *did_unlock)
+static void ext4_wait_dax_page(struct ext4_inode_info *ei)
{
- *did_unlock = true;
up_write(&ei->i_mmap_sem);
schedule();
down_write(&ei->i_mmap_sem);
@@ -4207,14 +4206,12 @@ int ext4_break_layouts(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct page *page;
- bool retry;
int error;
if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem)))
return -EINVAL;
do {
- retry = false;
page = dax_layout_busy_page(inode->i_mapping);
if (!page)
return 0;
@@ -4222,8 +4219,8 @@ int ext4_break_layouts(struct inode *inode)
error = ___wait_var_event(&page->_refcount,
atomic_read(&page->_refcount) == 1,
TASK_INTERRUPTIBLE, 0, 0,
- ext4_wait_dax_page(ei, &retry));
- } while (error == 0 && retry);
+ ext4_wait_dax_page(ei));
+ } while (error == 0);
return error;
}
--
2.16.4