[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] xen-blkfront: Use the bitmap API when applicable
Le 02/12/2021 à 19:16, Joe Perches a écrit : On Thu, 2021-12-02 at 19:12 +0100, Christophe JAILLET wrote:Le 02/12/2021 à 07:12, Juergen Gross a écrit :On 01.12.21 22:10, Christophe JAILLET wrote:Use 'bitmap_zalloc()' to simplify code, improve the semantic and avoid some open-coded arithmetic in allocator arguments. Also change the corresponding 'kfree()' into 'bitmap_free()' to keep consistency. Use 'bitmap_copy()' to avoid an explicit 'memcpy()'[]diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c[]@@ -442,16 +442,14 @@ static int xlbd_reserve_minors(unsigned int minor, unsigned int nr) if (end > nr_minors) { unsigned long *bitmap, *old; - bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap), - GFP_KERNEL); + bitmap = bitmap_zalloc(end, GFP_KERNEL); if (bitmap == NULL) return -ENOMEM; spin_lock(&minor_lock); if (end > nr_minors) { old = minors; - memcpy(bitmap, minors, - BITS_TO_LONGS(nr_minors) * sizeof(*bitmap)); + bitmap_copy(bitmap, minors, nr_minors); minors = bitmap; nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;nr_minors = end; ? No,My understanding of the code is that if we lack space (end > nr_minors), we need to allocate more. In such a case, we want to keep track of what we have allocated, not what we needed. The "padding" bits in the "long align" allocation, can be used later. first call ---------- end = 65 nr_minors = 63 --> we need some space --> we allocate 2 longs = 128 bits --> we now use 65 bits of these 128 bits new call -------- end = 68 nr_minors = 128 (from previous call) --> no need to reallocate CJ
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