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From: | Changlong Xie |
Subject: | Re: [Qemu-devel] [PATCH v10 2/3] quorum: implement bdrv_add_child() and bdrv_del_child() |
Date: | Mon, 7 Mar 2016 17:13:26 +0800 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 03/06/2016 02:13 AM, Max Reitz wrote:
On 16.02.2016 10:37, Changlong Xie wrote:From: Wen Congyang <address@hidden> Signed-off-by: Wen Congyang <address@hidden> Signed-off-by: zhanghailiang <address@hidden> Signed-off-by: Gonglei <address@hidden> Signed-off-by: Changlong Xie <address@hidden> --- block.c | 8 ++-- block/quorum.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++++- include/block/block.h | 4 ++ 3 files changed, 128 insertions(+), 6 deletions(-) diff --git a/block.c b/block.c index 08aa979..c3c9dc0 100644 --- a/block.c +++ b/block.c @@ -1198,10 +1198,10 @@ static int bdrv_fill_options(QDict **options, const char *filename, return 0; } -static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs, - BlockDriverState *child_bs, - const char *child_name, - const BdrvChildRole *child_role) +BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs, + BlockDriverState *child_bs, + const char *child_name, + const BdrvChildRole *child_role) { BdrvChild *child = g_new(BdrvChild, 1); *child = (BdrvChild) { diff --git a/block/quorum.c b/block/quorum.c index a5ae4b8..e5a7e4f 100644 --- a/block/quorum.c +++ b/block/quorum.c @@ -24,6 +24,7 @@ #include "qapi/qmp/qstring.h" #include "qapi-event.h" #include "crypto/hash.h" +#include "qemu/bitmap.h" #define HASH_LENGTH 32 @@ -81,6 +82,8 @@ typedef struct BDRVQuorumState { bool rewrite_corrupted;/* true if the driver must rewrite-on-read corrupted * block if Quorum is reached. */ + unsigned long *index_bitmap; + int bsize; QuorumReadPattern read_pattern; } BDRVQuorumState; @@ -876,9 +879,9 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags, ret = -EINVAL; goto exit; } - if (s->num_children < 2) { + if (s->num_children < 1) { error_setg(&local_err, - "Number of provided children must be greater than 1"); + "Number of provided children must be 1 or more");Side note: Actually, we could work with 0 children, too. Quorum would then need to implement bdrv_is_inserted() and return false if there are no children. But that is something that can be implemented later on if the need arises.
Hi Max Thanks for pointing it out.
ret = -EINVAL; goto exit; } @@ -927,6 +930,7 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags, /* allocate the children array */ s->children = g_new0(BdrvChild *, s->num_children); opened = g_new0(bool, s->num_children); + s->index_bitmap = bitmap_new(s->num_children); for (i = 0; i < s->num_children; i++) { char indexstr[32]; @@ -942,6 +946,8 @@ static int quorum_open(BlockDriverState *bs, QDict *options, int flags, opened[i] = true; } + bitmap_set(s->index_bitmap, 0, s->num_children); + s->bsize = s->num_children; g_free(opened); goto exit; @@ -998,6 +1004,115 @@ static void quorum_attach_aio_context(BlockDriverState *bs, } } +static int get_new_child_index(BDRVQuorumState *s) +{ + int index; + + index = find_next_zero_bit(s->index_bitmap, s->bsize, 0); + if (index < s->bsize) { + return index; + } + + if ((s->bsize % BITS_PER_LONG) == 0) { + s->index_bitmap = bitmap_zero_extend(s->index_bitmap, s->bsize, + s->bsize + 1);I think this function needs to be called unconditionally. Looking into its implementation, its call to g_realloc() will not do anything (and it will probably be pretty quick at that), but the following bitmap_clear()
Yes. If "BITS_TO_LONGS(new_nbits) == BITS_TO_LONGS(old_nbits)", g_realloc will do nothing.
will only clear the bits from old_nbits (s->bsize) to new_nbits (s->bsize + 1). Thus, if you only call this function every 32nd/64th child, only that child's bit will be initialized to zero. All the rest is undefined. You probably didn't notice because bitmap_new() returns a zero-initialized bitmap, and thus you'd have to create around 64 children (on an x64 machine) to notice
OOH! you're catching a *BIG* fish here. I'll remove the wrong "if" condition next version. *Thanks*
+ } + + return s->bsize++; +} + +static void remove_child_index(BDRVQuorumState *s, int index) +{ + int last_index; + long new_len;size_t would be the more appropriate type.
okay
+ + assert(index < s->bsize); + + clear_bit(index, s->index_bitmap); + if (index < s->bsize - 1) { + /* + * The last bit is always set, and we don't clears/don't/didn't/
I'm going to remove "and we don't clear the last bit" here.
+ * the last bit. + */ + return; + } + + last_index = find_last_bit(s->index_bitmap, s->bsize);An assert(last_index < s->bsize); here wouldn't hurt.
okay.
(last_index == s->bsize would be the case if no bit is set in s->index_bitmap anymore, which should be impossible.)+ s->bsize = last_index + 1; + if (BITS_TO_LONGS(last_index + 1) == BITS_TO_LONGS(s->bsize)) {
I correct myself here, it should be "BITS_TO_LONGS(old_bsize) == BITS_TO_LONGS(s->bsize)".
+ return; + } + + new_len = BITS_TO_LONGS(last_index + 1) * sizeof(unsigned long);s/last_index + 1/s->bsize/ looks better to me.
okay.
+ s->index_bitmap = g_realloc(s->index_bitmap, new_len); +} + +static void quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs, + Error **errp) +{ + BDRVQuorumState *s = bs->opaque; + BdrvChild *child; + char indexstr[32]; + int index, ret; + + index = get_new_child_index(s); + ret = snprintf(indexstr, 32, "children.%d", index); + if (ret < 0 || ret >= 32) { + error_setg(errp, "cannot generate child name"); + return; + } + + bdrv_drain(bs); + + assert(s->num_children <= INT_MAX / sizeof(BdrvChild *)); + if (s->num_children == INT_MAX / sizeof(BdrvChild *)) { + error_setg(errp, "Too many children"); + return; + } + s->children = g_renew(BdrvChild *, s->children, s->num_children + 1); + + bdrv_ref(child_bs); + child = bdrv_attach_child(bs, child_bs, indexstr, &child_format); + s->children[s->num_children++] = child; + set_bit(index, s->index_bitmap); +} + +static void quorum_del_child(BlockDriverState *bs, BlockDriverState *child_bs, + Error **errp) +{ + BDRVQuorumState *s = bs->opaque; + BdrvChild *child; + int i, index; + + for (i = 0; i < s->num_children; i++) { + if (s->children[i]->bs == child_bs) { + break; + } + } + + /* we have checked it in bdrv_del_child() */ + assert(i < s->num_children); + child = s->children[i]; + + if (s->num_children <= s->threshold) { + error_setg(errp, + "The number of children cannot be lower than the vote threshold %d", + s->threshold); + return; + } + + /* child->name is "children.%d" */Optional: assert(!strncmp(child->name, "children.", 9));+ index = atoi(child->name + 9);Optional: Assert absence of an error: unsigned long index; char *endptr; index = strtoul(child->name + 9, &endptr, 10); assert(index >= 0 && !*endptr);
Really useful, but since we strictly named 'child->name' in quorum_add_child, let's just keep the orignal one.
Thanks -Xie
Max+ + bdrv_drain(bs); + /* We can safely remove this child now */ + memmove(&s->children[i], &s->children[i + 1], + (s->num_children - i - 1) * sizeof(void *)); + s->children = g_renew(BdrvChild *, s->children, --s->num_children); + remove_child_index(s, index); + bdrv_unref_child(bs, child); +} + static void quorum_refresh_filename(BlockDriverState *bs, QDict *options) { BDRVQuorumState *s = bs->opaque; @@ -1053,6 +1168,9 @@ static BlockDriver bdrv_quorum = { .bdrv_detach_aio_context = quorum_detach_aio_context, .bdrv_attach_aio_context = quorum_attach_aio_context, + .bdrv_add_child = quorum_add_child, + .bdrv_del_child = quorum_del_child, + .is_filter = true, .bdrv_recurse_is_first_non_filter = quorum_recurse_is_first_non_filter, }; diff --git a/include/block/block.h b/include/block/block.h index ecde190..4b787d2 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -517,6 +517,10 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs); void bdrv_ref(BlockDriverState *bs); void bdrv_unref(BlockDriverState *bs); void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child); +BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs, + BlockDriverState *child_bs, + const char *child_name, + const BdrvChildRole *child_role); bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp); void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
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