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[PATCH 3.10 30/80] mmc: remove bondage between REQ_META and reliable write

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3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Luca Porzio <lporzio@micron.com>

commit d3df0465db00cf4ed9f90d0bfc3b827d32b9c796 upstream.

Anytime a write operation is performed with Reliable Write flag enabled,
the eMMC device is enforced to bypass the cache and do a write to the
underling NVM device by Jedec specification; this causes a performance
penalty since write operations can't be optimized by the device cache.

In our tests, we replayed a typical mobile daily trace pattern and found
~9% overall time reduction in trace replay by using this patch. Also the
write ops within 4KB~64KB chunk size range get a 40~60% performance
improvement by using the patch (as this range of write chunks are the ones
affected by REQ_META).

This patch has been discussed in the Mobile & Embedded Linux Storage Forum
and it's the results of feedbacks from many people. We also checked with
fsdevl and f2fs mailing list developers that this change in the usage of
REQ_META is not affecting FS behavior and we got positive feedbacks.
Reporting here the feedbacks:
http://comments.gmane.org/gmane.linux.file-systems/97219
http://thread.gmane.org/gmane.linux.file-systems.f2fs/3178/focus=3183

Signed-off-by: Bruce Ford <bford@micron.com>
Signed-off-by: Luca Porzio <lporzio@micron.com>
Fixes: ce39f9d17c14 ("mmc: support packed write command for eMMC4.5 devices")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/mmc/card/block.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -59,8 +59,7 @@ MODULE_ALIAS("mmc:block");
 #define INAND_CMD38_ARG_SECTRIM2 0x88
 #define MMC_BLK_TIMEOUT_MS  (10 * 60 * 1000)        /* 10 minute timeout */
 
-#define mmc_req_rel_wr(req)	(((req->cmd_flags & REQ_FUA) || \
-				  (req->cmd_flags & REQ_META)) && \
+#define mmc_req_rel_wr(req)	((req->cmd_flags & REQ_FUA) && \
 				  (rq_data_dir(req) == WRITE))
 #define PACKED_CMD_VER	0x01
 #define PACKED_CMD_WR	0x02
@@ -1300,13 +1299,9 @@ static void mmc_blk_rw_rq_prep(struct mm
 
 	/*
 	 * Reliable writes are used to implement Forced Unit Access and
-	 * REQ_META accesses, and are supported only on MMCs.
-	 *
-	 * XXX: this really needs a good explanation of why REQ_META
-	 * is treated special.
+	 * are supported only on MMCs.
 	 */
-	bool do_rel_wr = ((req->cmd_flags & REQ_FUA) ||
-			  (req->cmd_flags & REQ_META)) &&
+	bool do_rel_wr = (req->cmd_flags & REQ_FUA) &&
 		(rq_data_dir(req) == WRITE) &&
 		(md->flags & MMC_BLK_REL_WR);
 

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[PATCH 3.10 00/80] 3.10.99-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 08/80] dm thin metadata: fix bug when taking a metadata snapshot Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 02/80] drm/ast: Initialized data needed to map fbdev memory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 23/80] dts: vt8500: Add SDHC node to DTS file for WM8650 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 07/80] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 31/80] mac: validate mac_partition is within sector Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 14/80] proc: Fix ptrace-based permission checks for accessing task maps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 29/80] megaraid_sas : SMAP restriction--do not access user memory from IOCTL code Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 32/80] ARC: dw2 unwind: Remove falllback linear search thru FDE entries Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 11/80] USB: cp210x: add IDs for GE B650V3 and B850V3 boards Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 41/80] dm btree: fix bufio buffer leaks in dm_btree_del() error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 27/80] wm831x_power: Use IRQF_ONESHOT to request threaded IRQs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 10/80] can: ems_usb: Fix possible tx overflow Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 01/80] tracepoints: Do not trace when cpu is offline Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 06/80] drm/radeon: fix hotplug race at startup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 26/80] devres: fix a for loop bounds check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 30/80] mmc: remove bondage between REQ_META and reliable write Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 15/80] iw_cxgb3: Fix incorrectly returning error on success Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 35/80] virtio: fix memory leak of virtio ida cache layers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:40 +0100
  [PATCH 3.10 04/80] bcache: unregister reboot notifier if bcache fails to unregister device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:50 +0100
  Re: [PATCH 3.10 00/80] 3.10.99-stable review Guenter Roeck <linux@roeck-us.net> - 2016-03-02 15:40 +0100
    Re: [PATCH 3.10 00/80] 3.10.99-stable review Willy Tarreau <w@1wt.eu> - 2016-03-02 16:50 +0100
      Re: [PATCH 3.10 00/80] 3.10.99-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 18:30 +0100

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