This adds async buffered write support to iomap. The support is focused
on the changes necessary to support XFS with iomap.
Support for other filesystems might require additional changes.
Signed-off-by: Stefan Roesch <shr@xxxxxx>
---
fs/iomap/buffered-io.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 6b06fd358958..b029e2b10e07 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -580,12 +580,18 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
size_t from = offset_in_folio(folio, pos), to = from + len;
size_t poff, plen;
gfp_t gfp = GFP_NOFS | __GFP_NOFAIL;
+ bool no_wait = (iter->flags & IOMAP_NOWAIT);
+
+ if (no_wait)
+ gfp = GFP_NOWAIT;
if (folio_test_uptodate(folio))
return 0;
folio_clear_error(folio);
iop = iomap_page_create_gfp(iter->inode, folio, nr_blocks, gfp);
+ if (no_wait && !iop)
+ return -EAGAIN;
do {
iomap_adjust_read_range(iter->inode, folio, &block_start,
@@ -602,6 +608,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
if (WARN_ON_ONCE(iter->flags & IOMAP_UNSHARE))
return -EIO;
folio_zero_segments(folio, poff, from, to, poff + plen);
+ } else if (no_wait) {
+ return -EAGAIN;
} else {
int status = iomap_read_folio_sync(block_start, folio,
poff, plen, srcmap);
@@ -632,6 +640,9 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
int status = 0;
+ if (iter->flags & IOMAP_NOWAIT)
+ fgp |= FGP_NOWAIT;
+
BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
if (srcmap != &iter->iomap)
BUG_ON(pos + len > srcmap->offset + srcmap->length);
@@ -789,6 +800,10 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
+ *
+ * For async buffered writes the assumption is that the user
+ * page has already been faulted in. This can be optimized by
+ * faulting the user page in the prepare phase of io-uring.
*/
if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
status = -EFAULT;
@@ -844,6 +859,9 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
};
int ret;
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ iter.flags |= IOMAP_NOWAIT;
+
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_write_iter(&iter, i);
if (iter.pos == iocb->ki_pos)
--
2.30.2
