Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx> writes: > John Garry <john.g.garry@xxxxxxxxxx> writes: > >> From: Prasad Singamsetty <prasad.singamsetty@xxxxxxxxxx> >> >> An atomic write is a write issued with torn-write protection, meaning >> that for a power failure or any other hardware failure, all or none of the >> data from the write will be stored, but never a mix of old and new data. >> >> Userspace may add flag RWF_ATOMIC to pwritev2() to indicate that the >> write is to be issued with torn-write prevention, according to special >> alignment and length rules. >> >> For any syscall interface utilizing struct iocb, add IOCB_ATOMIC for >> iocb->ki_flags field to indicate the same. >> >> A call to statx will give the relevant atomic write info for a file: >> - atomic_write_unit_min >> - atomic_write_unit_max >> - atomic_write_segments_max >> >> Both min and max values must be a power-of-2. >> >> Applications can avail of atomic write feature by ensuring that the total >> length of a write is a power-of-2 in size and also sized between >> atomic_write_unit_min and atomic_write_unit_max, inclusive. Applications >> must ensure that the write is at a naturally-aligned offset in the file >> wrt the total write length. The value in atomic_write_segments_max >> indicates the upper limit for IOV_ITER iovcnt. >> >> Add file mode flag FMODE_CAN_ATOMIC_WRITE, so files which do not have the >> flag set will have RWF_ATOMIC rejected and not just ignored. >> >> Add a type argument to kiocb_set_rw_flags() to allows reads which have >> RWF_ATOMIC set to be rejected. >> >> Helper function atomic_write_valid() can be used by FSes to verify >> compliant writes. Minor nit. maybe generic_atomic_write_valid()?
