2013/9/24, OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>: > Namjae Jeon <linkinjeon@xxxxxxxxx> writes: > >>>> We considered after your advice before. we reach for the conclusion >>>> that use this method. >>>> because, Cluster is already allocated in fat fallocate and >>>> when we write with radom offset over i_size on fallocated region, It >>>> will be hit by fat cache in fat_bmap of get_block, which mean buffer >>>> is not set to new. >>> >>> Hm, how does it hit to fat cache? I think fat_alloc_clusters() and >>> fat_chain_add() doesn't update fat cache, right? I.e. initial write >>> after fallocate() should not hit fat cache over i_size? >> >> Ah.. Sorry for wrong reply. old memory make me confusing. >> By allocating cluster in fat fallocate, when write, fat_bmap of >> get_block return physical sector number. >> So buffer is not set to new in _fat_get_block. >> >> When we fallocate with keep size on -> only clusters are added to the >> fat chain calling fat_get_cluster(),and add the cluster to cluster >> chain. >> This doesn’t call fat_get_block() . > > Right. > >> Now when we try to write in the fallocated region in the >> fat_write_begin() when it is called first time it checks that the >> mismatch is present between the mmu_private and mmu_actual (i.e., the >> file has pre-allocated blocks), and hence zero out the region ; >> Since buffer_new() is not set for fallocated region by fat_get_block() >> , we explicitly zero out the lseek'ed region using >> “fat_zero_falloc_area” and normal write occurs beyond that,and i_size >> is updated accordingly. > > Yes. So I'm saying fixing fat_get_block() would not be hard. > > For example, add new size the disk_size, totally 3 sizes - 1) i_size 2) > mmu_private (aka, initialized size) 3) disk_size (aka, uninitialized > size). > > When called fat_get_block(), it checks the region between mmu_private > and disk_size. If block hits that region, block is uninitialized area, > so return as buffer_new(). > > Like this, I think it is not hard. Please consider like above example > too. Yes, I checked after change as your suggestion. it work fine. I will post the updated patch soon. Thanks. OGAWA. > > Thanks. > -- > OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
