pagecache_get_page — find and get a page reference
| struct page * pagecache_get_page ( | struct address_space * mapping, | 
| pgoff_t offset, | |
| int fgp_flags, | |
| gfp_t gfp_mask ); | 
mappingthe address_space to search
offsetthe page index
fgp_flagsPCG flags
gfp_maskgfp mask to use for the page cache data page allocation
   Looks up the page cache slot at mapping & offset.
   
PCG flags modify how the page is returned.
   If page is not present then a new page is allocated using
   gfp_mask and added to the page cache and the VM's LRU
   list. The page is returned locked and with an increased
   refcount. Otherwise, NULL is returned.
   
If FGP_LOCK or FGP_CREAT are specified then the function may sleep even if the GFP flags specified for FGP_CREAT are atomic.
If there is a page cache page, it is returned with an increased refcount.