Add iomap buffered write support for RWF_DONTCACHE. If RWF_DONTCACHE is
set for a write, mark the folios being written as uncached. Then
writeback completion will drop the pages. The write_iter handler simply
kicks off writeback for the pages, and writeback completion will take
care of the rest.
Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
Documentation/filesystems/iomap/design.rst | 5 +++++
Documentation/filesystems/iomap/operations.rst | 2 ++
fs/iomap/buffered-io.c | 4 ++++
include/linux/iomap.h | 1 +
4 files changed, 12 insertions(+)
diff --git a/Documentation/filesystems/iomap/design.rst b/Documentation/filesystems/iomap/design.rst
index b0d0188a095e..7b91546750f5 100644
--- a/Documentation/filesystems/iomap/design.rst
+++ b/Documentation/filesystems/iomap/design.rst
@@ -352,6 +352,11 @@ operations:
``IOMAP_NOWAIT`` is often set on behalf of ``IOCB_NOWAIT`` or
``RWF_NOWAIT``.
+ * ``IOMAP_DONTCACHE`` is set when the caller wishes to perform a
+ buffered file I/O and would like the kernel to drop the pagecache
+ after the I/O completes, if it isn't already being used by another
+ thread.
+
If it is necessary to read existing file contents from a `different
<https://lore.kernel.org/all/20191008071527.29304-9-hch@xxxxxx/>`_
device or address range on a device, the filesystem should return that
diff --git a/Documentation/filesystems/iomap/operations.rst b/Documentation/filesystems/iomap/operations.rst
index 2c7f5df9d8b0..584ff549f9a6 100644
--- a/Documentation/filesystems/iomap/operations.rst
+++ b/Documentation/filesystems/iomap/operations.rst
@@ -131,6 +131,8 @@ These ``struct kiocb`` flags are significant for buffered I/O with iomap:
* ``IOCB_NOWAIT``: Turns on ``IOMAP_NOWAIT``.
+ * ``IOCB_DONTCACHE``: Turns on ``IOMAP_DONTCACHE``.
+
Internal per-Folio State
------------------------
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d303e6c8900c..ea863c3cf510 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -603,6 +603,8 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)
if (iter->flags & IOMAP_NOWAIT)
fgp |= FGP_NOWAIT;
+ if (iter->flags & IOMAP_DONTCACHE)
+ fgp |= FGP_DONTCACHE;
fgp |= fgf_set_order(len);
return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
@@ -1034,6 +1036,8 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
if (iocb->ki_flags & IOCB_NOWAIT)
iter.flags |= IOMAP_NOWAIT;
+ if (iocb->ki_flags & IOCB_DONTCACHE)
+ iter.flags |= IOMAP_DONTCACHE;
while ((ret = iomap_iter(&iter, ops)) > 0)
iter.processed = iomap_write_iter(&iter, i);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 75bf54e76f3b..26b0dbe23e62 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -183,6 +183,7 @@ struct iomap_folio_ops {
#define IOMAP_DAX 0
#endif /* CONFIG_FS_DAX */
#define IOMAP_ATOMIC (1 << 9)
+#define IOMAP_DONTCACHE (1 << 10)
struct iomap_ops {
/*
--
2.47.2
