[Qemu-devel] [PATCH 1/7] block: add discard support

[Christoph Hellwig <hch@lst.de>]

Add a new bdrv_discard method to free blocks in a mapping image, and a new
drive property to set the granularity for these discard.  If no discard
granularity support is set discard support is disabled.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: qemu/block.c
===================================================================
--- qemu.orig/block.c	2010-12-07 09:34:17.563010201 +0100
+++ qemu/block.c	2010-12-07 09:37:44.734255486 +0100
@@ -1499,6 +1499,17 @@ int bdrv_has_zero_init(BlockDriverState
     return 1;
 }
 
+int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
+{
+    if (!bs->drv) {
+        return -ENOMEDIUM;
+    }
+    if (!bs->drv->bdrv_discard) {
+        return 0;
+    }
+    return bs->drv->bdrv_discard(bs, sector_num, nb_sectors);
+}
+
 /*
  * Returns true iff the specified sector is present in the disk image. Drivers
  * not implementing the functionality are assumed to not support backing files,
Index: qemu/block.h
===================================================================
--- qemu.orig/block.h	2010-12-07 09:34:17.571010061 +0100
+++ qemu/block.h	2010-12-07 09:34:29.689022144 +0100
@@ -146,6 +146,7 @@ int bdrv_flush(BlockDriverState *bs);
 void bdrv_flush_all(void);
 void bdrv_close_all(void);
 
+int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
 int bdrv_has_zero_init(BlockDriverState *bs);
 int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
 	int *pnum);
Index: qemu/block_int.h
===================================================================
--- qemu.orig/block_int.h	2010-12-07 09:34:17.588010480 +0100
+++ qemu/block_int.h	2010-12-07 09:34:29.693010131 +0100
@@ -73,6 +73,8 @@ struct BlockDriver {
         BlockDriverCompletionFunc *cb, void *opaque);
     BlockDriverAIOCB *(*bdrv_aio_flush)(BlockDriverState *bs,
         BlockDriverCompletionFunc *cb, void *opaque);
+    int (*bdrv_discard)(BlockDriverState *bs, int64_t sector_num,
+                        int nb_sectors);
 
     int (*bdrv_aio_multiwrite)(BlockDriverState *bs, BlockRequest *reqs,
         int num_reqs);
@@ -227,6 +229,7 @@ typedef struct BlockConf {
     uint16_t logical_block_size;
     uint16_t min_io_size;
     uint32_t opt_io_size;
+    uint32_t discard_granularity;
 } BlockConf;
 
 static inline unsigned int get_physical_block_exp(BlockConf *conf)
@@ -249,6 +252,8 @@ static inline unsigned int get_physical_
     DEFINE_PROP_UINT16("physical_block_size", _state,                   \
                        _conf.physical_block_size, 512),                 \
     DEFINE_PROP_UINT16("min_io_size", _state, _conf.min_io_size, 0),  \
-    DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0)
+    DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0), \
+    DEFINE_PROP_UINT32("discard_granularity", _state, \
+                       _conf.discard_granularity, 0)
 
 #endif /* BLOCK_INT_H */
Index: qemu/block/raw.c
===================================================================
--- qemu.orig/block/raw.c	2010-12-07 09:34:17.596025496 +0100
+++ qemu/block/raw.c	2010-12-07 09:34:29.695297321 +0100
@@ -65,6 +65,11 @@ static int raw_probe(const uint8_t *buf,
    return 1; /* everything can be opened as raw image */
 }
 
+static int raw_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
+{
+    return bdrv_discard(bs->file, sector_num, nb_sectors);
+}
+
 static int raw_is_inserted(BlockDriverState *bs)
 {
     return bdrv_is_inserted(bs->file);
@@ -130,6 +135,7 @@ static BlockDriver bdrv_raw = {
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
     .bdrv_aio_flush     = raw_aio_flush,
+    .bdrv_discard       = raw_discard,
 
     .bdrv_is_inserted   = raw_is_inserted,
     .bdrv_eject         = raw_eject,