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raw-posix: handle > 512 byte alignment correctly 

Replace the hardcoded handling of 512 byte alignment with bs->buffer_alignment
to handle larger sector size devices correctly.

Note that we can not rely on it to be initialize in bdrv_open, so deal
with the worst case there.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Christoph Hellwig 2010-09-12 23:43:21 +02:00 committed by Kevin Wolf
parent 72aef7318f
commit 581b9e29f3
1 changed files with 46 additions and 33 deletions
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77
block/raw-posix.c
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@ -97,12 +97,12 @@
#define FTYPE_CD 1
#define FTYPE_FD 2
#define ALIGNED_BUFFER_SIZE (32 * 512)
/* if the FD is not accessed during that time (in ms), we try to
reopen it to see if the disk has been changed */
#define FD_OPEN_TIMEOUT 1000
#define MAX_BLOCKSIZE 4096
typedef struct BDRVRawState {
int fd;
int type;
@ -119,6 +119,7 @@ typedef struct BDRVRawState {
void *aio_ctx;
#endif
uint8_t *aligned_buf;
unsigned aligned_buf_size;
} BDRVRawState;
static int fd_open(BlockDriverState *bs);
@ -161,7 +162,12 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
s->aligned_buf = NULL;
if ((bdrv_flags & BDRV_O_NOCACHE)) {
s->aligned_buf = qemu_blockalign(bs, ALIGNED_BUFFER_SIZE);
/*
* Allocate a buffer for read/modify/write cycles. Chose the size
* pessimistically as we don't know the block size yet.
*/
s->aligned_buf_size = 32 * MAX_BLOCKSIZE;
s->aligned_buf = qemu_memalign(MAX_BLOCKSIZE, s->aligned_buf_size);
if (s->aligned_buf == NULL) {
goto out_close;
}
@ -278,8 +284,9 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset,
}
/*
* offset and count are in bytes, but must be multiples of 512 for files
* opened with O_DIRECT. buf must be aligned to 512 bytes then.
* offset and count are in bytes, but must be multiples of the sector size
* for files opened with O_DIRECT. buf must be aligned to sector size bytes
* then.
*
* This function may be called without alignment if the caller ensures
* that O_DIRECT is not in effect.
@ -316,24 +323,25 @@ static int raw_pread(BlockDriverState *bs, int64_t offset,
uint8_t *buf, int count)
{
BDRVRawState *s = bs->opaque;
unsigned sector_mask = bs->buffer_alignment - 1;
int size, ret, shift, sum;
sum = 0;
if (s->aligned_buf != NULL) {
if (offset & 0x1ff) {
/* align offset on a 512 bytes boundary */
if (offset & sector_mask) {
/* align offset on a sector size bytes boundary */
shift = offset & 0x1ff;
size = (shift + count + 0x1ff) & ~0x1ff;
if (size > ALIGNED_BUFFER_SIZE)
size = ALIGNED_BUFFER_SIZE;
shift = offset & sector_mask;
size = (shift + count + sector_mask) & ~sector_mask;
if (size > s->aligned_buf_size)
size = s->aligned_buf_size;
ret = raw_pread_aligned(bs, offset - shift, s->aligned_buf, size);
if (ret < 0)
return ret;
size = 512 - shift;
size = bs->buffer_alignment - shift;
if (size > count)
size = count;
memcpy(buf, s->aligned_buf + shift, size);
@ -346,15 +354,15 @@ static int raw_pread(BlockDriverState *bs, int64_t offset,
if (count == 0)
return sum;
}
if (count & 0x1ff || (uintptr_t) buf & 0x1ff) {
if (count & sector_mask || (uintptr_t) buf & sector_mask) {
/* read on aligned buffer */
while (count) {
size = (count + 0x1ff) & ~0x1ff;
if (size > ALIGNED_BUFFER_SIZE)
size = ALIGNED_BUFFER_SIZE;
size = (count + sector_mask) & ~sector_mask;
if (size > s->aligned_buf_size)
size = s->aligned_buf_size;
ret = raw_pread_aligned(bs, offset, s->aligned_buf, size);
if (ret < 0) {
@ -404,25 +412,28 @@ static int raw_pwrite(BlockDriverState *bs, int64_t offset,
const uint8_t *buf, int count)
{
BDRVRawState *s = bs->opaque;
unsigned sector_mask = bs->buffer_alignment - 1;
int size, ret, shift, sum;
sum = 0;
if (s->aligned_buf != NULL) {
if (offset & 0x1ff) {
/* align offset on a 512 bytes boundary */
shift = offset & 0x1ff;
ret = raw_pread_aligned(bs, offset - shift, s->aligned_buf, 512);
if (offset & sector_mask) {
/* align offset on a sector size bytes boundary */
shift = offset & sector_mask;
ret = raw_pread_aligned(bs, offset - shift, s->aligned_buf,
bs->buffer_alignment);
if (ret < 0)
return ret;
size = 512 - shift;
size = bs->buffer_alignment - shift;
if (size > count)
size = count;
memcpy(s->aligned_buf + shift, buf, size);
ret = raw_pwrite_aligned(bs, offset - shift, s->aligned_buf, 512);
ret = raw_pwrite_aligned(bs, offset - shift, s->aligned_buf,
bs->buffer_alignment);
if (ret < 0)
return ret;
@ -434,12 +445,12 @@ static int raw_pwrite(BlockDriverState *bs, int64_t offset,
if (count == 0)
return sum;
}
if (count & 0x1ff || (uintptr_t) buf & 0x1ff) {
if (count & sector_mask || (uintptr_t) buf & sector_mask) {
while ((size = (count & ~0x1ff)) != 0) {
while ((size = (count & ~sector_mask)) != 0) {
if (size > ALIGNED_BUFFER_SIZE)
size = ALIGNED_BUFFER_SIZE;
if (size > s->aligned_buf_size)
size = s->aligned_buf_size;
memcpy(s->aligned_buf, buf, size);
@ -452,14 +463,16 @@ static int raw_pwrite(BlockDriverState *bs, int64_t offset,
count -= ret;
sum += ret;
}
/* here, count < 512 because (count & ~0x1ff) == 0 */
/* here, count < 512 because (count & ~sector_mask) == 0 */
if (count) {
ret = raw_pread_aligned(bs, offset, s->aligned_buf, 512);
ret = raw_pread_aligned(bs, offset, s->aligned_buf,
bs->buffer_alignment);
if (ret < 0)
return ret;
memcpy(s->aligned_buf, buf, count);
ret = raw_pwrite_aligned(bs, offset, s->aligned_buf, 512);
ret = raw_pwrite_aligned(bs, offset, s->aligned_buf,
bs->buffer_alignment);
if (ret < 0)
return ret;
if (count < ret)
@ -487,12 +500,12 @@ static int raw_write(BlockDriverState *bs, int64_t sector_num,
/*
* Check if all memory in this vector is sector aligned.
*/
static int qiov_is_aligned(QEMUIOVector *qiov)
static int qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
{
int i;
for (i = 0; i < qiov->niov; i++) {
if ((uintptr_t) qiov->iov[i].iov_base % BDRV_SECTOR_SIZE) {
if ((uintptr_t) qiov->iov[i].iov_base % bs->buffer_alignment) {
return 0;
}
}
@ -515,7 +528,7 @@ static BlockDriverAIOCB *raw_aio_submit(BlockDriverState *bs,
* driver that it needs to copy the buffer.
*/
if (s->aligned_buf) {
if (!qiov_is_aligned(qiov)) {
if (!qiov_is_aligned(bs, qiov)) {
type |= QEMU_AIO_MISALIGNED;
#ifdef CONFIG_LINUX_AIO
} else if (s->use_aio) {