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authorMinchan Kim <minchan@kernel.org>2017-11-16 04:33:00 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-16 05:21:02 +0300
commit23c47d2ada9f96731492a67b28c0072715075baa (patch)
treedbe8a9322eab448997e27b19b1b39b235eaddd2a /include/linux/backing-dev.h
parente447a0151f7ce8dd884fea48279274bd64434c29 (diff)
downloadlinux-23c47d2ada9f96731492a67b28c0072715075baa.tar.xz
bdi: introduce BDI_CAP_SYNCHRONOUS_IO
As discussed at https://lkml.kernel.org/r/<20170728165604.10455-1-ross.zwisler@linux.intel.com> someday we will remove rw_page(). If so, we need something to detect such super-fast storage on which synchronous IO operations like the current rw_page are always a win. Introduces BDI_CAP_SYNCHRONOUS_IO to indicate such devices. With it, we could use various optimization techniques. Link: http://lkml.kernel.org/r/1505886205-9671-3-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/backing-dev.h')
-rw-r--r--include/linux/backing-dev.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index f41ca8486e02..7360e79e9a2f 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -122,6 +122,8 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
* BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
*
* BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
+ * BDI_CAP_SYNCHRONOUS_IO: Device is so fast that asynchronous IO would be
+ * inefficient.
*/
#define BDI_CAP_NO_ACCT_DIRTY 0x00000001
#define BDI_CAP_NO_WRITEBACK 0x00000002
@@ -129,6 +131,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
#define BDI_CAP_STABLE_WRITES 0x00000008
#define BDI_CAP_STRICTLIMIT 0x00000010
#define BDI_CAP_CGROUP_WRITEBACK 0x00000020
+#define BDI_CAP_SYNCHRONOUS_IO 0x00000040
#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
@@ -174,6 +177,11 @@ static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
long congestion_wait(int sync, long timeout);
long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout);
+static inline bool bdi_cap_synchronous_io(struct backing_dev_info *bdi)
+{
+ return bdi->capabilities & BDI_CAP_SYNCHRONOUS_IO;
+}
+
static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
{
return bdi->capabilities & BDI_CAP_STABLE_WRITES;