diff options
| author | Max Reitz <mreitz@redhat.com> | 2016-11-15 23:57:45 +0100 |
|---|---|---|
| committer | Fam Zheng <famz@redhat.com> | 2017-01-26 10:25:01 +0800 |
| commit | 20a579de8484096d18e65751ebe63fee31551f04 (patch) | |
| tree | b18432ea3cce4bb67817676b72a8c1e2ee0c3bb3 | |
| parent | c7f1cf01b8245762ca5864e835d84f6677ae8b1f (diff) | |
hbitmap: Add hbitmap_is_serializable()
Bitmaps with a granularity of 58 or above can be neither serialized nor
deserialized (see the comment in the function added in this series for
an explanation). This patch adds a function so that we can check whether
a bitmap actually can be (de-)serialized at all, thus avoiding failing
the necessary assertion in hbitmap_serialization_granularity().
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20161115225746.3590-2-mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
| -rw-r--r-- | include/qemu/hbitmap.h | 13 | ||||
| -rw-r--r-- | util/hbitmap.c | 22 |
2 files changed, 32 insertions, 3 deletions
diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h index eb464759d5..9239fe515e 100644 --- a/include/qemu/hbitmap.h +++ b/include/qemu/hbitmap.h @@ -146,6 +146,19 @@ void hbitmap_reset_all(HBitmap *hb); bool hbitmap_get(const HBitmap *hb, uint64_t item); /** + * hbitmap_is_serializable: + * @hb: HBitmap which should be (de-)serialized. + * + * Returns whether the bitmap can actually be (de-)serialized. Other + * (de-)serialization functions may only be invoked if this function returns + * true. + * + * Calling (de-)serialization functions does not affect a bitmap's + * (de-)serializability. + */ +bool hbitmap_is_serializable(const HBitmap *hb); + +/** * hbitmap_serialization_granularity: * @hb: HBitmap to operate on. * diff --git a/util/hbitmap.c b/util/hbitmap.c index 9f691b76bd..35088e19c4 100644 --- a/util/hbitmap.c +++ b/util/hbitmap.c @@ -387,6 +387,24 @@ void hbitmap_reset_all(HBitmap *hb) hb->count = 0; } +bool hbitmap_is_serializable(const HBitmap *hb) +{ + /* Every serialized chunk must be aligned to 64 bits so that endianness + * requirements can be fulfilled on both 64 bit and 32 bit hosts. + * We have hbitmap_serialization_granularity() which converts this + * alignment requirement from bitmap bits to items covered (e.g. sectors). + * That value is: + * 64 << hb->granularity + * Since this value must not exceed UINT64_MAX, hb->granularity must be + * less than 58 (== 64 - 6, where 6 is ld(64), i.e. 1 << 6 == 64). + * + * In order for hbitmap_serialization_granularity() to always return a + * meaningful value, bitmaps that are to be serialized must have a + * granularity of less than 58. */ + + return hb->granularity < 58; +} + bool hbitmap_get(const HBitmap *hb, uint64_t item) { /* Compute position and bit in the last layer. */ @@ -399,9 +417,7 @@ bool hbitmap_get(const HBitmap *hb, uint64_t item) uint64_t hbitmap_serialization_granularity(const HBitmap *hb) { - /* Must hold true so that the shift below is defined - * (ld(64) == 6, i.e. 1 << 6 == 64) */ - assert(hb->granularity < 64 - 6); + assert(hbitmap_is_serializable(hb)); /* Require at least 64 bit granularity to be safe on both 64 bit and 32 bit * hosts. */ |