page
gfp_mask
The address_space is to try to release any data against the page (presumably at page->private). If the release was successful, return `1'. Otherwise return zero.
This may also be called if PG_fscache is set on a page, indicating that the page is known to the local caching routines.
The gfp_mask argument specifies whether I/O may be performed to release this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).