search for: ___wait_var_event

On Fri, Sep 25, 2020 at 01:44:41PM -0700, Ralph Campbell wrote: > error = ___wait_var_event(&page->_refcount, > - atomic_read(&page->_refcount) == 1, > + dax_layout_is_idle_page(page), > TASK_INTERRUPTIBLE, 0, 0, > ext4_wait_dax_page(ei)); > +++ b/fs/xfs/xfs_file.c > @@ -750,7 +750,7 @@ xfs_break_dax_layouts( > > *retry = true; &g...

...yout_is_idle_page(page)) return page; } return NULL; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index bf596467c234..4c3b80e68121 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3926,10 +3926,7 @@ int ext4_break_layouts(struct inode *inode) if (!page) return 0; - error = ___wait_var_event(&page->_refcount, - atomic_read(&page->_refcount) == 1, - TASK_INTERRUPTIBLE, 0, 0, - ext4_wait_dax_page(ei)); + error = dax_wait_page(ei, page, ext4_wait_dax_page); } while (error == 0); return error; diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 3d1b951247...

...he 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, 0, ext4_wait_dax_page(ei)); } while (error == 0); diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index a29f78a663ca..29ab96541bc1 100644 --- a/fs/xfs/x...

...* > 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, 0, > ext4_wait_dax_page(ei)); &...

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

This is still an RFC because after looking at the pmem/dax code some more, I realized that the ZONE_DEVICE struct pages are being inserted into the process' page tables with vmf_insert_mixed() and a zero refcount on the ZONE_DEVICE struct page. This is sort of OK because insert_pfn() increments the reference count on the pgmap which is what prevents memunmap_pages() from freeing the struct