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Re: [Qemu-devel] [PATCH 5/6] parallels: use pread
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 5/6] parallels: use pread |
Date: |
Wed, 05 May 2010 16:19:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 |
Am 04.05.2010 12:45, schrieb Christoph Hellwig:
> Use pread instead of lseek + read in preparation of using the qemu
> block API.
>
> Signed-off-by: Christoph Hellwig <address@hidden>
>
> Index: qemu-kevin/block/parallels.c
> ===================================================================
> --- qemu-kevin.orig/block/parallels.c 2010-05-03 13:00:09.711253925 +0200
> +++ qemu-kevin/block/parallels.c 2010-05-03 13:04:15.686033993 +0200
> @@ -83,7 +83,7 @@ static int parallels_open(BlockDriverSta
>
> s->fd = fd;
>
> - if (read(fd, &ph, sizeof(ph)) != sizeof(ph))
> + if (pread(fd, &ph, sizeof(ph), 0) != sizeof(ph))
> goto fail;
>
> if (memcmp(ph.magic, HEADER_MAGIC, 16) ||
> @@ -93,14 +93,11 @@ static int parallels_open(BlockDriverSta
>
> bs->total_sectors = le32_to_cpu(ph.nb_sectors);
>
> - if (lseek(s->fd, 64, SEEK_SET) != 64)
> - goto fail;
> -
> s->tracks = le32_to_cpu(ph.tracks);
>
> s->catalog_size = le32_to_cpu(ph.catalog_entries);
> s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
> - if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
> + if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4, 64) !=
> s->catalog_size * 4)
> goto fail;
> for (i = 0; i < s->catalog_size; i++)
> @@ -114,28 +111,18 @@ fail:
> return -1;
> }
>
> -static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
> +static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
> {
> BDRVParallelsState *s = bs->opaque;
> uint32_t index, offset;
> - uint64_t position;
>
> index = sector_num / s->tracks;
> offset = sector_num % s->tracks;
>
> - // not allocated
> + /* not allocated */
> if ((index > s->catalog_size) || (s->catalog_bitmap[index] == 0))
> return -1;
> -
> - position = (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
> -
> -// fprintf(stderr, "sector: %llx index=%x offset=%x pointer=%x
> position=%x\n",
> -// sector_num, index, offset, s->catalog_bitmap[index], position);
> -
> - if (lseek(s->fd, position, SEEK_SET) != position)
> - return -1;
> -
> - return 0;
> + return (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
> }
>
> static int parallels_read(BlockDriverState *bs, int64_t sector_num,
> @@ -144,11 +131,13 @@ static int parallels_read(BlockDriverSta
> BDRVParallelsState *s = bs->opaque;
>
> while (nb_sectors > 0) {
> - if (!seek_to_sector(bs, sector_num)) {
> - if (read(s->fd, buf, 512) != 512)
> - return -1;
> - } else
> + uint64_t position = seek_to_sector(bs, sector_num);
> + if (position >= 0) {
position should be a signed int64_t, otherwise the condition is always true.
Kevin
- [Qemu-devel] simple block driver cleanups, Christoph Hellwig, 2010/05/04
- [Qemu-devel] [PATCH 2/6] bochs: use qemu block API, Christoph Hellwig, 2010/05/04
- [Qemu-devel] [PATCH 3/6] cloop: use pread, Christoph Hellwig, 2010/05/04
- [Qemu-devel] [PATCH 4/6] cloop: use qemu block API, Christoph Hellwig, 2010/05/04
- [Qemu-devel] [PATCH 5/6] parallels: use pread, Christoph Hellwig, 2010/05/04
- Re: [Qemu-devel] [PATCH 5/6] parallels: use pread,
Kevin Wolf <=
- [Qemu-devel] [PATCH 6/6] parallels: use qemu block API, Christoph Hellwig, 2010/05/04
- Re: [Qemu-devel] simple block driver cleanups, Kevin Wolf, 2010/05/04