readahead_gfp_mask
readahead_gfp_mask(as) & ~__GFP_RECLAIM);
gfp_t ra_gfp_mask = readahead_gfp_mask(mapping) & ~__GFP_FS;
gfp_t gfp_mask = readahead_gfp_mask(mapping);
gfp_t gfp = readahead_gfp_mask(mapping);
gfp_t gfp_mask = readahead_gfp_mask(mapping);