From 848c66e8f5b631961580f7f010a5831430dc84c2 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 20 Oct 2011 13:16:21 +0200 Subject: [PATCH] block: add a CoMutex to synchronous read drivers The big conversion of bdrv_read/write to coroutines caused the two homonymous callbacks in BlockDriver to become reentrant. It goes like this: 1) bdrv_read is now called in a coroutine, and calls bdrv_read or bdrv_pread. 2) the nested bdrv_read goes through the fast path in bdrv_rw_co_entry; 3) in the common case when the protocol is file, bdrv_co_do_readv calls bdrv_co_readv_em (and from here goes to bdrv_co_io_em), which yields until the AIO operation is complete; 4) if bdrv_read had been called from a bottom half, the main loop is free to iterate again: a device model or another bottom half can then come and call bdrv_read again. This applies to all four of read/write/flush/discard. It would also apply to is_allocated, but it is not used from within coroutines: besides qemu-img.c and qemu-io.c, which operate synchronously, the only user is the monitor. Copy-on-read will introduce a use in the block layer, and will require converting it. The solution is "simply" to convert all drivers to coroutines! We just need to add a CoMutex that is taken around affected operations. Signed-off-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- block/bochs.c | 2 ++ block/cloop.c | 2 ++ block/cow.c | 2 ++ block/dmg.c | 2 ++ block/nbd.c | 2 ++ block/parallels.c | 2 ++ block/vmdk.c | 2 ++ block/vpc.c | 2 ++ block/vvfat.c | 2 ++ 9 files changed, 18 insertions(+) diff --git a/block/bochs.c b/block/bochs.c index 3c2f8d1b12..b0f80729fe 100644 --- a/block/bochs.c +++ b/block/bochs.c @@ -80,6 +80,7 @@ struct bochs_header { }; typedef struct BDRVBochsState { + CoMutex lock; uint32_t *catalog_bitmap; int catalog_size; @@ -150,6 +151,7 @@ static int bochs_open(BlockDriverState *bs, int flags) s->extent_size = le32_to_cpu(bochs.extra.redolog.extent); + qemu_co_mutex_init(&s->lock); return 0; fail: return -1; diff --git a/block/cloop.c b/block/cloop.c index 8cff9f2cac..a91f372aec 100644 --- a/block/cloop.c +++ b/block/cloop.c @@ -27,6 +27,7 @@ #include typedef struct BDRVCloopState { + CoMutex lock; uint32_t block_size; uint32_t n_blocks; uint64_t* offsets; @@ -93,6 +94,7 @@ static int cloop_open(BlockDriverState *bs, int flags) s->sectors_per_block = s->block_size/512; bs->total_sectors = s->n_blocks*s->sectors_per_block; + qemu_co_mutex_init(&s->lock); return 0; cloop_close: diff --git a/block/cow.c b/block/cow.c index 4cf543c832..2f426e7427 100644 --- a/block/cow.c +++ b/block/cow.c @@ -42,6 +42,7 @@ struct cow_header_v2 { }; typedef struct BDRVCowState { + CoMutex lock; int64_t cow_sectors_offset; } BDRVCowState; @@ -84,6 +85,7 @@ static int cow_open(BlockDriverState *bs, int flags) bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header); s->cow_sectors_offset = (bitmap_size + 511) & ~511; + qemu_co_mutex_init(&s->lock); return 0; fail: return -1; diff --git a/block/dmg.c b/block/dmg.c index 64c3cce46a..111aeaecd9 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -28,6 +28,7 @@ #include typedef struct BDRVDMGState { + CoMutex lock; /* each chunk contains a certain number of sectors, * offsets[i] is the offset in the .dmg file, * lengths[i] is the length of the compressed chunk, @@ -177,6 +178,7 @@ static int dmg_open(BlockDriverState *bs, int flags) s->current_chunk = s->n_chunks; + qemu_co_mutex_init(&s->lock); return 0; fail: return -1; diff --git a/block/nbd.c b/block/nbd.c index 76f04d863c..14ab2259c2 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -47,6 +47,7 @@ #endif typedef struct BDRVNBDState { + CoMutex lock; int sock; uint32_t nbdflags; off_t size; @@ -175,6 +176,7 @@ static int nbd_open(BlockDriverState *bs, const char* filename, int flags) */ result = nbd_establish_connection(bs); + qemu_co_mutex_init(&s->lock); return result; } diff --git a/block/parallels.c b/block/parallels.c index c64103ddbb..b86e87e48f 100644 --- a/block/parallels.c +++ b/block/parallels.c @@ -46,6 +46,7 @@ struct parallels_header { } QEMU_PACKED; typedef struct BDRVParallelsState { + CoMutex lock; uint32_t *catalog_bitmap; int catalog_size; @@ -95,6 +96,7 @@ static int parallels_open(BlockDriverState *bs, int flags) for (i = 0; i < s->catalog_size; i++) le32_to_cpus(&s->catalog_bitmap[i]); + qemu_co_mutex_init(&s->lock); return 0; fail: if (s->catalog_bitmap) diff --git a/block/vmdk.c b/block/vmdk.c index ace29774f4..1ce220d535 100644 --- a/block/vmdk.c +++ b/block/vmdk.c @@ -90,6 +90,7 @@ typedef struct VmdkExtent { } VmdkExtent; typedef struct BDRVVmdkState { + CoMutex lock; int desc_offset; bool cid_updated; uint32_t parent_cid; @@ -646,6 +647,7 @@ static int vmdk_open(BlockDriverState *bs, int flags) goto fail; } s->parent_cid = vmdk_read_cid(bs, 1); + qemu_co_mutex_init(&s->lock); return ret; fail: diff --git a/block/vpc.c b/block/vpc.c index cb6c570f44..9155ee15e3 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -110,6 +110,7 @@ struct vhd_dyndisk_header { }; typedef struct BDRVVPCState { + CoMutex lock; uint8_t footer_buf[HEADER_SIZE]; uint64_t free_data_block_offset; int max_table_entries; @@ -226,6 +227,7 @@ static int vpc_open(BlockDriverState *bs, int flags) s->last_pagetable = -1; #endif + qemu_co_mutex_init(&s->lock); return 0; fail: return err; diff --git a/block/vvfat.c b/block/vvfat.c index 7e9e35a3a3..864bfcf245 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -317,6 +317,7 @@ static void print_mapping(const struct mapping_t* mapping); /* here begins the real VVFAT driver */ typedef struct BDRVVVFATState { + CoMutex lock; BlockDriverState* bs; /* pointer to parent */ unsigned int first_sectors_number; /* 1 for a single partition, 0x40 for a disk with partition table */ unsigned char first_sectors[0x40*0x200]; @@ -1065,6 +1066,7 @@ DLOG(if (stderr == NULL) { bs->heads = bs->cyls = bs->secs = 0; // assert(is_consistent(s)); + qemu_co_mutex_init(&s->lock); return 0; }