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...->count == 1. A filesystem uses this interface to determine if + * page->count == 0. A filesystem uses this interface to determine if * any page in the mapping is busy, i.e. for DMA, or other * get_user_pages() usages. * diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index bf596467c234..d9f8ad55523a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3927,7 +3927,7 @@ int ext4_break_layouts(struct inode *inode) return 0; error = ___wait_var_event(&page->_refcount, - atomic_read(&page->_refcount) == 1, + dax_layout_is_idle_page(page), TASK_INTERRUPTIBLE, 0,...

...uses this interface to determine if > + * page->count == 0. A filesystem uses this interface to determine if > * any page in the mapping is busy, i.e. for DMA, or other > * get_user_pages() usages. > * > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index bf596467c234..d9f8ad55523a 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3927,7 +3927,7 @@ int ext4_break_layouts(struct inode *inode) > return 0; > > error = ___wait_var_event(&page->_refcount, > - atomic_read(&a...

Matthew Wilcox, Ira Weiny, and others have complained that ZONE_DEVICE struct page reference counting is ugly because they are "free" when the reference count is one instead of zero. This leads to explicit checks for ZONE_DEVICE pages in places like put_page(), GUP, THP splitting, and page migration which have to adjust the expected reference count when determining if the page is