From 89791ede6270659dc2aad31b63d1b84017526e2c Mon Sep 17 00:00:00 2001 From: Jeffrey Cody Date: Wed, 21 Mar 2012 21:54:53 +0100 Subject: [PATCH 26/55] block: add interface to toggle copy-on-read RH-Author: Jeffrey Cody Message-id: <91b8b89e2ca8556a3eb9b873dec78208ee21b749.1332362400.git.jcody@redhat.com> Patchwork-id: 38876 O-Subject: [RHEL6.3 qemu-kvm PATCH v8 26/54] block: add interface to toggle copy-on-read Bugzilla: 582475 RH-Acked-by: Paolo Bonzini RH-Acked-by: Marcelo Tosatti RH-Acked-by: Kevin Wolf From: Stefan Hajnoczi The bdrv_enable_copy_on_read()/bdrv_disable_copy_on_read() functions can be used to programmatically enable or disable copy-on-read for a block device. Later patches add the actual copy-on-read logic. Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf (cherry picked from commit 53fec9d3fd3d3a4ded4b92dfa843436bf71380f1) Signed-off-by: Stefan Hajnoczi Signed-off-by: Anthony Liguori Signed-off-by: Jeff Cody --- block.c | 22 ++++++++++++++++++++++ block.h | 4 ++++ block_int.h | 2 ++ 3 files changed, 28 insertions(+), 0 deletions(-) Signed-off-by: Michal Novotny --- block.c | 22 ++++++++++++++++++++++ block.h | 4 ++++ block_int.h | 2 ++ 3 files changed, 28 insertions(+), 0 deletions(-) diff --git a/block.c b/block.c index 50d80fe..c2a2493 100644 --- a/block.c +++ b/block.c @@ -420,6 +420,22 @@ static int refresh_total_sectors(BlockDriverState *bs, int64_t hint) return 0; } +/** + * The copy-on-read flag is actually a reference count so multiple users may + * use the feature without worrying about clobbering its previous state. + * Copy-on-read stays enabled until all users have called to disable it. + */ +void bdrv_enable_copy_on_read(BlockDriverState *bs) +{ + bs->copy_on_read++; +} + +void bdrv_disable_copy_on_read(BlockDriverState *bs) +{ + assert(bs->copy_on_read > 0); + bs->copy_on_read--; +} + /* * Common part for opening disk images and files */ @@ -438,6 +454,11 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename, /* buffer_alignment defaulted to 512, drivers can change this value */ bs->buffer_alignment = 512; + assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */ + if ((flags & BDRV_O_RDWR) && (flags & BDRV_O_COPY_ON_READ)) { + bdrv_enable_copy_on_read(bs); + } + pstrcpy(bs->filename, sizeof(bs->filename), filename); if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv)) { @@ -671,6 +692,7 @@ void bdrv_close(BlockDriverState *bs) #endif bs->opaque = NULL; bs->drv = NULL; + bs->copy_on_read = 0; if (bs->file != NULL) { bdrv_close(bs->file); diff --git a/block.h b/block.h index 330ed10..9b4a3a5 100644 --- a/block.h +++ b/block.h @@ -69,6 +69,7 @@ typedef struct BlockDevOps { #define BDRV_O_NATIVE_AIO 0x0080 /* use native AIO instead of the thread pool */ #define BDRV_O_NO_BACKING 0x0100 /* don't open the backing file */ #define BDRV_O_NO_FLUSH 0x0200 /* disable flushing on this disk */ +#define BDRV_O_COPY_ON_READ 0x0400 /* copy read backing sectors into image */ #define BDRV_O_INCOMING 0x0800 /* consistency hint for incoming migration */ #define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB) @@ -299,6 +300,9 @@ int bdrv_get_dirty(BlockDriverState *bs, int64_t sector); void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors); +void bdrv_enable_copy_on_read(BlockDriverState *bs); +void bdrv_disable_copy_on_read(BlockDriverState *bs); + void bdrv_set_in_use(BlockDriverState *bs, int in_use); int bdrv_in_use(BlockDriverState *bs); diff --git a/block_int.h b/block_int.h index f3cd33a..bdda1af 100644 --- a/block_int.h +++ b/block_int.h @@ -165,6 +165,8 @@ struct BlockDriverState { int encrypted; /* if true, the media is encrypted */ int valid_key; /* if true, a valid encryption key has been set */ int sg; /* if true, the device is a /dev/sg* */ + int copy_on_read; /* if true, copy read backing sectors into image + note this is a reference count */ BlockDriver *drv; /* NULL means no media */ void *opaque; -- 1.7.7.6