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block/raw-posix.c: add BLKDISCARD support

PATCH In review e-t172 2 participants 2 messages Nov 11, 2011 – Nov 14, 2011 Block layer

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#0 lore raw

PATCH 1/1 block/raw-posix.c: add BLKDISCARD support

This adds ioctl(BLKDISCARD) (a.k.a "discard", "TRIM", "UNMAP", "hole punching") support for host devices. This is especially useful if the raw device is a SSD or some kind of thin-provisioned device.

Cc Kevin Wolf <[email protected]>
Signed-off-by Etienne Dechamps <[email protected]>
---
 block/raw-posix.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)
block/raw-posix.c +20 -0
index a3de373..d6eac66 100644
@@ -104,6 +104,10 @@
 #define O_DIRECT O_DSYNC
 #endif
 
+#ifndef BLKDISCARD
+#define BLKDISCARD _IO(0x12, 119)
+#endif
+
 #define FTYPE_FILE   0
 #define FTYPE_CD     1
 #define FTYPE_FD     2

@@ -892,6 +896,21 @@ static int hdev_has_zero_init(BlockDriverState *bs)
     return 0;
 }
 
+static int hdev_co_discard(BlockDriverState *bs, int64_t sector_num,
+                        int nb_sectors)
+{
+    BDRVRawState *s = bs->opaque;
+    int fd = s->fd;
+    uint64_t range[2];
+
+    range[0] = sector_num << 9;
+    range[1] = nb_sectors << 9;
+    if (ioctl(fd, BLKDISCARD, &range)) {
+        return -errno;
+    }
+    return 0;
+}
+
 static BlockDriver bdrv_host_device = {
     .format_name        = "host_device",
     .protocol_name        = "host_device",

@@ -902,6 +921,7 @@ static BlockDriver bdrv_host_device = {
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
     .bdrv_has_zero_init = hdev_has_zero_init,
+    .bdrv_co_discard       = hdev_co_discard,
 
     .bdrv_aio_readv    = raw_aio_readv,
     .bdrv_aio_writev   = raw_aio_writev,
Signature · 6 lines
1.7.7.1


-- 
Etienne Dechamps / e-t172 - AKE Group
Phone: +33 6 23 42 24 82
#1 lore raw
Quoted 4 lines · On Fri, Nov 11, 2011 at 8:56 PM, e-t172 <[email protected]> wrote:
block/raw-posix.c +4 -0
+static int hdev_co_discard(BlockDriverState *bs, int64_t sector_num,
+                        int nb_sectors)
+{
+    BDRVRawState *s = bs->opaque;

block/raw-posix.c static int hdev_has_zero_init(BlockDriverState *bs) · line 912

Quoted 10 lines
block/raw-posix.c +10 -0
+    int fd = s->fd;
+    uint64_t range[2];
+
+    range[0] = sector_num << 9;
+    range[1] = nb_sectors << 9;
+    if (ioctl(fd, BLKDISCARD, &range)) {
+        return -errno;
+    }
+    return 0;
+}

Is ioctl(BLKDISCARD) guaranteed non-blocking? I think we need to use paio_ioctl() here instead to do this asynchronously.

Let's also be careful about Linux-specific ioctls. This code should not poke an unsupported ioctl() on OSes which do not support BLKDISCARD. We definitely need a plan when #if !defined(__linux__).

Stefan