diff options
| author | Christoph Hellwig <hch@lst.de> | 2025-11-13 18:06:28 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-11-25 10:22:18 +0100 |
| commit | 29086a31b3abc662d0571ed6a938937ec1e1ec0a (patch) | |
| tree | 051d17550e5b024c00fec47d454f29f0f64efab5 | |
| parent | ddb4873286e03e193c5a3bebb5fc6fa820e9ee3a (diff) | |
| download | linux-29086a31b3abc662d0571ed6a938937ec1e1ec0a.tar.gz | |
iomap: rework REQ_FUA selection
The way how iomap_dio_can_use_fua and the caller is structured is
a bit confusing, as the main guarding condition is hidden in the
helper, and the secondary conditions are split between caller and
callee.
Refactor the code, so that iomap_dio_bio_iter itself tracks if a write
might need metadata updates based on the iomap type and flags, and
then have a condition based on that to use the FUA flag.
Note that this also moves the REQ_OP_WRITE assignment to the end of
the branch to improve readability a bit.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20251113170633.1453259-4-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/iomap/direct-io.c | 78 |
1 files changed, 48 insertions, 30 deletions
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 765ab6dd66374f..fb2d83f640efe0 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -287,23 +287,6 @@ static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, return 0; } -/* - * Use a FUA write if we need datasync semantics and this is a pure data I/O - * that doesn't require any metadata updates (including after I/O completion - * such as unwritten extent conversion) and the underlying device either - * doesn't have a volatile write cache or supports FUA. - * This allows us to avoid cache flushes on I/O completion. - */ -static inline bool iomap_dio_can_use_fua(const struct iomap *iomap, - struct iomap_dio *dio) -{ - if (iomap->flags & (IOMAP_F_SHARED | IOMAP_F_DIRTY)) - return false; - if (!(dio->flags & IOMAP_DIO_WRITE_THROUGH)) - return false; - return !bdev_write_cache(iomap->bdev) || bdev_fua(iomap->bdev); -} - static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) { const struct iomap *iomap = &iter->iomap; @@ -332,7 +315,24 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) return -EINVAL; if (dio->flags & IOMAP_DIO_WRITE) { - bio_opf |= REQ_OP_WRITE; + bool need_completion_work = true; + + switch (iomap->type) { + case IOMAP_MAPPED: + /* + * Directly mapped I/O does not inherently need to do + * work at I/O completion time. But there are various + * cases below where this will get set again. + */ + need_completion_work = false; + break; + case IOMAP_UNWRITTEN: + dio->flags |= IOMAP_DIO_UNWRITTEN; + need_zeroout = true; + break; + default: + break; + } if (iomap->flags & IOMAP_F_ATOMIC_BIO) { /* @@ -345,22 +345,40 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) bio_opf |= REQ_ATOMIC; } - if (iomap->type == IOMAP_UNWRITTEN) { - dio->flags |= IOMAP_DIO_UNWRITTEN; - need_zeroout = true; - } - - if (iomap->flags & IOMAP_F_SHARED) + if (iomap->flags & IOMAP_F_SHARED) { + /* + * Unsharing of needs to update metadata at I/O + * completion time. + */ + need_completion_work = true; dio->flags |= IOMAP_DIO_COW; + } - if (iomap->flags & IOMAP_F_NEW) + if (iomap->flags & IOMAP_F_NEW) { + /* + * Newly allocated blocks might need recording in + * metadata at I/O completion time. + */ + need_completion_work = true; need_zeroout = true; - else if (iomap->type == IOMAP_MAPPED && - iomap_dio_can_use_fua(iomap, dio)) - bio_opf |= REQ_FUA; + } - if (!(bio_opf & REQ_FUA)) - dio->flags &= ~IOMAP_DIO_WRITE_THROUGH; + /* + * Use a FUA write if we need datasync semantics and this is a + * pure overwrite that doesn't require any metadata updates. + * + * This allows us to avoid cache flushes on I/O completion. + */ + if (dio->flags & IOMAP_DIO_WRITE_THROUGH) { + if (!need_completion_work && + !(iomap->flags & IOMAP_F_DIRTY) && + (!bdev_write_cache(iomap->bdev) || + bdev_fua(iomap->bdev))) + bio_opf |= REQ_FUA; + else + dio->flags &= ~IOMAP_DIO_WRITE_THROUGH; + } + bio_opf |= REQ_OP_WRITE; } else { bio_opf |= REQ_OP_READ; } |