FAT_START_ENT
return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus
return FAT_START_ENT <= entry && entry < sbi->max_cluster;
count = FAT_START_ENT;
fatent.entry = FAT_START_ENT;
fatent_set_entry(&fatent, FAT_START_ENT);
ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
sbi->prev_free = FAT_START_ENT;
total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
sbi->max_cluster = total_clusters + FAT_START_ENT;
if (sbi->prev_free < FAT_START_ENT)
sbi->prev_free = FAT_START_ENT;
buf->f_blocks = sbi->max_cluster - FAT_START_ENT;