From: Ross Zwisler <zwisler(a)kernel.org&gt; 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. Note that this works around the race exposed by my unit test, but I think that there is another race that needs to be addressed, probably with additional synchronization added between direct I/O and {ext4,xfs}_break_layouts(). Signed-off-by: Ross Zwisler <ross.zwisler(a)linux.intel.com&gt; Reviewed-by: Jan Kara <jack(a)suse.cz&gt; --- 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 8f6ad7667974..d2663a1e3ec2 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4191,9 +4191,8 @@ 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); @@ -4203,14 +4202,12 @@ 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; @@ -4218,8 +4215,8 @@ 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; }