If a file system supports uncached buffered IO, it may set FOP_UNCACHED
and enable RWF_UNCACHED. If RWF_UNCACHED is attempted without the file
system supporting it, it'll get errored with -EOPNOTSUPP.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/linux/fs.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3559446279c1..491eeb73e725 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2116,6 +2116,8 @@ struct file_operations {
#define FOP_HUGE_PAGES ((__force fop_flags_t)(1 << 4))
/* Treat loff_t as unsigned (e.g., /dev/mem) */
#define FOP_UNSIGNED_OFFSET ((__force fop_flags_t)(1 << 5))
+/* File system supports uncached read/write buffered IO */
+#define FOP_UNCACHED ((__force fop_flags_t)(1 << 6))
/* Wrap a directory iterator that needs exclusive inode access */
int wrap_directory_iterator(struct file *, struct dir_context *,
@@ -3532,6 +3534,10 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags,
if (!(ki->ki_filp->f_mode & FMODE_CAN_ATOMIC_WRITE))
return -EOPNOTSUPP;
}
+ if (flags & RWF_UNCACHED) {
+ if (!(ki->ki_filp->f_op->fop_flags & FOP_UNCACHED))
+ return -EOPNOTSUPP;
+ }
kiocb_flags |= (__force int) (flags & RWF_SUPPORTED);
if (flags & RWF_SYNC)
kiocb_flags |= IOCB_DSYNC;
--
2.45.2
