On 10/26, Christoph Hellwig wrote: > On Thu, Oct 26, 2017 at 04:30:19PM +0200, Jaegeuk Kim wrote: > > On 10/26, Yunlong Song wrote: > > > f2fs_balance_fs only actives once in the commit_inmem_pages, but there > > > are more than one page to commit, so all the other pages will miss the > > > check. This will lead to out-of-free problem when commit a very large > > > file. To fix it, we should do f2fs_balance_fs for each inmem page. > > > > NAK, this breaks atomicity. > > Can someone please explain (and write down in e.g. manpages) these > atomicy rules? The basic idea is to provide atomicity of blocks written by write(2) given period managed by user. For example, user can do 1) ioctl to start a period, 2) write(2) calls, 3) ioctl to commit all the blocks. Then, filesystem will guarantee committed blocks should be recovered all or nothing after power-cut. Scenario #1: - ioctl(fd, F2FS_IOC_START_ATOMIC_WRITE) - 0 = write(2) - ... - 0 = write(2) - ioctl(fd, F2FS_IOC_COMMIT_ATOMIC_WRITE) Scenario #2: - ioctl(fd, F2FS_IOC_START_ATOMIC_WRITE) - 0 = write(2) - ... - err = write(2) - ioctl(fd, F2FS_IOC_ABORT_ATOMIC_WRITE) Scenario #3: - ioctl(fd, F2FS_IOC_START_ATOMIC_WRITE) - 0 = write(2) - ... - process crashed or close(fd) Thanks,
