From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O9fSH-0002Nb-63 for qemu-devel@nongnu.org; Wed, 05 May 2010 10:20:05 -0400 Received: from [140.186.70.92] (port=41415 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O9fSF-0002Lh-Ja for qemu-devel@nongnu.org; Wed, 05 May 2010 10:20:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O9fSA-0004V6-Nh for qemu-devel@nongnu.org; Wed, 05 May 2010 10:20:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55596) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O9fSA-0004Ub-EC for qemu-devel@nongnu.org; Wed, 05 May 2010 10:19:58 -0400 Message-ID: <4BE17E72.4020308@redhat.com> Date: Wed, 05 May 2010 16:19:30 +0200 From: Kevin Wolf MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 5/6] parallels: use pread References: <20100504104351.GA6342@lst.de> <20100504104504.GE6388@lst.de> In-Reply-To: <20100504104504.GE6388@lst.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christoph Hellwig Cc: qemu-devel@nongnu.org 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 > > 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