>majianpeng <majianpeng@xxxxxxxxx> writes: > >>>majianpeng <majianpeng@xxxxxxxxx> writes: >>> >>>> For async-write on block device,if device removed,but the vfs don't know it. >>>> It will continue to do. >>>> Patch1 set size of inode of block device to zero when removed disk.By this,vfs know >>>> disk changed. >>>> Path2 add size-check on blk_aio_write.If pos of write larger than size of inode,it will >>>> return zero.So the user can check disk state. >>> >>>OK, so the basic problem is that __generic_file_aio_write will always >>>return 0 after device removal, yes? I'm not sure why that's a real >>>issue, can you explain exactly why you're trying to change this? >>> >> At prenset, the __generic_file_aio_write don't return zero rather that the wanted size. >> So the user can't know the disk removed. >> For example: >> dd if=/dev/zero of=usb-disk bs=64k >> When removed usb-disk, dd stoped until reached the endof usb-disk. > >Ah, right, it's just writing to the page cache. I think the only reason >you get more timely errors when doing the same thing to a file on a file >system is that there is some synchronous metadata or journal I/O that >will get EIO and result in the file system being set read-only. > Yes >The bigger question is whether we want to change this long-standing >behaviour of how our write-back cache works. I don't know that it's >really worth it, honestly. If you want to ensure data is on disk, you >open the file O_SYNC or you issue an fsync, and those calls will return >an error for a removed block device. So, I guess I'll ask the same >question again: why are you looking at this? Is there some application >you care about that does buffered I/O to the block device and never does >an fsync? > Yes, for my company, we used our filesystem in userspace on block-device. For the performance, we used buffer-wrtite not sync-write. For my workload, we allow user to remove disk whether disk working or not. Now, we check the state of disk from /proc/partitions at the same interval. This patchset don't change write-back cache works.It only let vfs know the state of lower-device. I think it make a sense. Thanks! Jianpeng Ma?韬{.n?????%??檩??w?{.n???{饼?z鳐??骅w*jg????????G??⒏⒎?:+v????????????"??????