Whether we have a write back cache and are using FUA or don't have a write back cache at all is the same situation. Treat them the same. This makes the IOMAP_DIO_WRITE_FUA name a bit misleading, as we have two cases that provide stable writes: 1) Volatile write cache with FUA writes 2) Normal write without a volatile write cache Rename that flag to IOMAP_DIO_STABLE_WRITE to make that clearer, and update some of the FUA comments as well. Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- fs/iomap/direct-io.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index c654612b24e5..17b695b0e9d6 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -21,7 +21,7 @@ * iomap.h: */ #define IOMAP_DIO_INLINE_COMP (1 << 27) -#define IOMAP_DIO_WRITE_FUA (1 << 28) +#define IOMAP_DIO_WRITE_THROUGH (1 << 28) #define IOMAP_DIO_NEED_SYNC (1 << 29) #define IOMAP_DIO_WRITE (1 << 30) #define IOMAP_DIO_DIRTY (1 << 31) @@ -222,7 +222,7 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, /* * Figure out the bio's operation flags from the dio request, the * mapping, and whether or not we want FUA. Note that we can end up - * clearing the WRITE_FUA flag in the dio request. + * clearing the WRITE_THROUGH flag in the dio request. */ static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio, const struct iomap *iomap, bool use_fua) @@ -236,7 +236,7 @@ static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio, if (use_fua) opflags |= REQ_FUA; else - dio->flags &= ~IOMAP_DIO_WRITE_FUA; + dio->flags &= ~IOMAP_DIO_WRITE_THROUGH; return opflags; } @@ -276,11 +276,13 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, * Use a FUA write if we need datasync semantics, this is a pure * data IO that doesn't require any metadata updates (including * after IO completion such as unwritten extent conversion) and - * the underlying device supports FUA. This allows us to avoid - * cache flushes on IO completion. + * the underlying device either supports FUA or doesn't have + * a volatile write cache. This allows us to avoid cache flushes + * on IO completion. */ if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) && - (dio->flags & IOMAP_DIO_WRITE_FUA) && bdev_fua(iomap->bdev)) + (dio->flags & IOMAP_DIO_WRITE_THROUGH) && + (bdev_fua(iomap->bdev) || !bdev_write_cache(iomap->bdev))) use_fua = true; } @@ -560,12 +562,15 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, /* * For datasync only writes, we optimistically try - * using FUA for this IO. Any non-FUA write that - * occurs will clear this flag, hence we know before - * completion whether a cache flush is necessary. + * using WRITE_THROUGH for this IO. Stable writes are + * either FUA with a write cache, or a normal write to + * a device without a volatile write cache. For the + * former, Any non-FUA write that occurs will clear this + * flag, hence we know before completion whether a cache + * flush is necessary. */ if (!(iocb->ki_flags & IOCB_SYNC)) - dio->flags |= IOMAP_DIO_WRITE_FUA; + dio->flags |= IOMAP_DIO_WRITE_THROUGH; } /* @@ -627,10 +632,10 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, iomap_dio_set_error(dio, ret); /* - * If all the writes we issued were FUA, we don't need to flush the + * If all the writes we issued were stable, we don't need to flush the * cache on IO completion. Clear the sync flag for this case. */ - if (dio->flags & IOMAP_DIO_WRITE_FUA) + if (dio->flags & IOMAP_DIO_WRITE_THROUGH) dio->flags &= ~IOMAP_DIO_NEED_SYNC; WRITE_ONCE(iocb->private, dio->submit.poll_bio); -- 2.40.1
