* [Qemu-devel] [PATCH 1/6] bochs: use pread
@ 2010-05-04 10:44 Christoph Hellwig
2010-05-04 11:20 ` Roy Tam
2010-05-05 13:17 ` Anthony Liguori
0 siblings, 2 replies; 4+ messages in thread
From: Christoph Hellwig @ 2010-05-04 10:44 UTC (permalink / raw)
To: qemu-devel
Use pread instead of lseek + read in preparation of using the qemu
block API.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Index: qemu-kevin/block/bochs.c
===================================================================
--- qemu-kevin.orig/block/bochs.c 2010-05-03 12:58:53.419012621 +0200
+++ qemu-kevin/block/bochs.c 2010-05-03 12:59:13.873005360 +0200
@@ -125,7 +125,7 @@ static int bochs_open(BlockDriverState *
s->fd = fd;
- if (read(fd, &bochs, sizeof(bochs)) != sizeof(bochs)) {
+ if (pread(fd, &bochs, sizeof(bochs), 0) != sizeof(bochs)) {
goto fail;
}
@@ -144,14 +144,10 @@ static int bochs_open(BlockDriverState *
bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
}
- if (lseek(s->fd, le32_to_cpu(bochs.header), SEEK_SET) == (off_t)-1) {
- goto fail;
- }
-
s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
- if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
- s->catalog_size * 4)
+ if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4,
+ le32_to_cpu(bochs.header)) != s->catalog_size * 4)
goto fail;
for (i = 0; i < s->catalog_size; i++)
le32_to_cpus(&s->catalog_bitmap[i]);
@@ -169,54 +165,35 @@ static int bochs_open(BlockDriverState *
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)
{
BDRVBochsState *s = bs->opaque;
int64_t offset = sector_num * 512;
- int64_t extent_index, extent_offset, bitmap_offset, block_offset;
+ int64_t extent_index, extent_offset, bitmap_offset;
char bitmap_entry;
// seek to sector
extent_index = offset / s->extent_size;
extent_offset = (offset % s->extent_size) / 512;
- if (s->catalog_bitmap[extent_index] == 0xffffffff)
- {
-// fprintf(stderr, "page not allocated [%x - %x:%x]\n",
-// sector_num, extent_index, extent_offset);
- return -1; // not allocated
+ if (s->catalog_bitmap[extent_index] == 0xffffffff) {
+ return -1; /* not allocated */
}
bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
(s->extent_blocks + s->bitmap_blocks));
- block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
-// fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
-// sector_num, extent_index, extent_offset,
-// le32_to_cpu(s->catalog_bitmap[extent_index]),
-// bitmap_offset, block_offset);
-
- // read in bitmap for current extent
- if (lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET) ==
- (off_t)-1) {
+ /* read in bitmap for current extent */
+ if (pread(s->fd, &bitmap_entry, 1, bitmap_offset + (extent_offset / 8))
+ != 1) {
return -1;
}
- if (read(s->fd, &bitmap_entry, 1) != 1)
- return -1;
-
- if (!((bitmap_entry >> (extent_offset % 8)) & 1))
- {
-// fprintf(stderr, "sector (%x) in bitmap not allocated\n",
-// sector_num);
- return -1; // not allocated
+ if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
+ return -1; /* not allocated */
}
- if (lseek(s->fd, block_offset, SEEK_SET) == (off_t)-1) {
- return -1;
- }
-
- return 0;
+ return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
}
static int bochs_read(BlockDriverState *bs, int64_t sector_num,
@@ -226,13 +203,13 @@ static int bochs_read(BlockDriverState *
int ret;
while (nb_sectors > 0) {
- if (!seek_to_sector(bs, sector_num))
- {
- ret = read(s->fd, buf, 512);
- if (ret != 512)
- return -1;
- }
- else
+ int64_t block_offset = seek_to_sector(bs, sector_num);
+ if (block_offset >= 0) {
+ ret = pread(s->fd, buf, 512, block_offset);
+ if (ret != 512) {
+ return -1;
+ }
+ } else
memset(buf, 0, 512);
nb_sectors--;
sector_num++;
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH 1/6] bochs: use pread
2010-05-04 10:44 [Qemu-devel] [PATCH 1/6] bochs: use pread Christoph Hellwig
@ 2010-05-04 11:20 ` Roy Tam
2010-05-04 11:39 ` Christoph Hellwig
2010-05-05 13:17 ` Anthony Liguori
1 sibling, 1 reply; 4+ messages in thread
From: Roy Tam @ 2010-05-04 11:20 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: qemu-devel
2010/5/4 Christoph Hellwig <hch@lst.de>:
> Use pread instead of lseek + read in preparation of using the qemu
> block API.
>
IIRC there is no pread in MinGW.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH 1/6] bochs: use pread
2010-05-04 11:20 ` Roy Tam
@ 2010-05-04 11:39 ` Christoph Hellwig
0 siblings, 0 replies; 4+ messages in thread
From: Christoph Hellwig @ 2010-05-04 11:39 UTC (permalink / raw)
To: Roy Tam; +Cc: Christoph Hellwig, qemu-devel
On Tue, May 04, 2010 at 07:20:22PM +0800, Roy Tam wrote:
> 2010/5/4 Christoph Hellwig <hch@lst.de>:
> > Use pread instead of lseek + read in preparation of using the qemu
> > block API.
> >
>
> IIRC there is no pread in MinGW.
It gets replaced in the next patch anyway.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH 1/6] bochs: use pread
2010-05-04 10:44 [Qemu-devel] [PATCH 1/6] bochs: use pread Christoph Hellwig
2010-05-04 11:20 ` Roy Tam
@ 2010-05-05 13:17 ` Anthony Liguori
1 sibling, 0 replies; 4+ messages in thread
From: Anthony Liguori @ 2010-05-05 13:17 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: Kevin Wolf, qemu-devel
On 05/04/2010 05:44 AM, Christoph Hellwig wrote:
> Use pread instead of lseek + read in preparation of using the qemu
> block API.
>
> Signed-off-by: Christoph Hellwig<hch@lst.de>
>
Looks good to me.
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Regards,
Anthony Liguori
> Index: qemu-kevin/block/bochs.c
> ===================================================================
> --- qemu-kevin.orig/block/bochs.c 2010-05-03 12:58:53.419012621 +0200
> +++ qemu-kevin/block/bochs.c 2010-05-03 12:59:13.873005360 +0200
> @@ -125,7 +125,7 @@ static int bochs_open(BlockDriverState *
>
> s->fd = fd;
>
> - if (read(fd,&bochs, sizeof(bochs)) != sizeof(bochs)) {
> + if (pread(fd,&bochs, sizeof(bochs), 0) != sizeof(bochs)) {
> goto fail;
> }
>
> @@ -144,14 +144,10 @@ static int bochs_open(BlockDriverState *
> bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
> }
>
> - if (lseek(s->fd, le32_to_cpu(bochs.header), SEEK_SET) == (off_t)-1) {
> - goto fail;
> - }
> -
> s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
> s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
> - if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
> - s->catalog_size * 4)
> + if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4,
> + le32_to_cpu(bochs.header)) != s->catalog_size * 4)
> goto fail;
> for (i = 0; i< s->catalog_size; i++)
> le32_to_cpus(&s->catalog_bitmap[i]);
> @@ -169,54 +165,35 @@ static int bochs_open(BlockDriverState *
> 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)
> {
> BDRVBochsState *s = bs->opaque;
> int64_t offset = sector_num * 512;
> - int64_t extent_index, extent_offset, bitmap_offset, block_offset;
> + int64_t extent_index, extent_offset, bitmap_offset;
> char bitmap_entry;
>
> // seek to sector
> extent_index = offset / s->extent_size;
> extent_offset = (offset % s->extent_size) / 512;
>
> - if (s->catalog_bitmap[extent_index] == 0xffffffff)
> - {
> -// fprintf(stderr, "page not allocated [%x - %x:%x]\n",
> -// sector_num, extent_index, extent_offset);
> - return -1; // not allocated
> + if (s->catalog_bitmap[extent_index] == 0xffffffff) {
> + return -1; /* not allocated */
> }
>
> bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
> (s->extent_blocks + s->bitmap_blocks));
> - block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
>
> -// fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
> -// sector_num, extent_index, extent_offset,
> -// le32_to_cpu(s->catalog_bitmap[extent_index]),
> -// bitmap_offset, block_offset);
> -
> - // read in bitmap for current extent
> - if (lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET) ==
> - (off_t)-1) {
> + /* read in bitmap for current extent */
> + if (pread(s->fd,&bitmap_entry, 1, bitmap_offset + (extent_offset / 8))
> + != 1) {
> return -1;
> }
>
> - if (read(s->fd,&bitmap_entry, 1) != 1)
> - return -1;
> -
> - if (!((bitmap_entry>> (extent_offset % 8))& 1))
> - {
> -// fprintf(stderr, "sector (%x) in bitmap not allocated\n",
> -// sector_num);
> - return -1; // not allocated
> + if (!((bitmap_entry>> (extent_offset % 8))& 1)) {
> + return -1; /* not allocated */
> }
>
> - if (lseek(s->fd, block_offset, SEEK_SET) == (off_t)-1) {
> - return -1;
> - }
> -
> - return 0;
> + return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
> }
>
> static int bochs_read(BlockDriverState *bs, int64_t sector_num,
> @@ -226,13 +203,13 @@ static int bochs_read(BlockDriverState *
> int ret;
>
> while (nb_sectors> 0) {
> - if (!seek_to_sector(bs, sector_num))
> - {
> - ret = read(s->fd, buf, 512);
> - if (ret != 512)
> - return -1;
> - }
> - else
> + int64_t block_offset = seek_to_sector(bs, sector_num);
> + if (block_offset>= 0) {
> + ret = pread(s->fd, buf, 512, block_offset);
> + if (ret != 512) {
> + return -1;
> + }
> + } else
> memset(buf, 0, 512);
> nb_sectors--;
> sector_num++;
>
>
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2010-05-05 13:17 UTC | newest]
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2010-05-04 10:44 [Qemu-devel] [PATCH 1/6] bochs: use pread Christoph Hellwig
2010-05-04 11:20 ` Roy Tam
2010-05-04 11:39 ` Christoph Hellwig
2010-05-05 13:17 ` Anthony Liguori
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