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block: more read-only changes, related to backing files 

Open backing file read-only where possible
Upgrade backing file to read-write during commit, back to read-only after commit
  If upgrade fail, back to read-only. If also fail, "disconnect" the drive.

Signed-off-by: Naphtali Sprei <nsprei@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Naphtali Sprei 2010-02-14 13:39:18 +02:00 committed by Anthony Liguori
parent e94a793648
commit 4dca4b639c
2 changed files with 73 additions and 12 deletions
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83
block.c
View File

@ -363,6 +363,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
bs->is_temporary = 0;
bs->encrypted = 0;
bs->valid_key = 0;
bs->open_flags = flags;
/* buffer_alignment defaulted to 512, drivers can change this value */
bs->buffer_alignment = 512;
@ -450,8 +451,6 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
bs->enable_write_cache = 1;
bs->read_only = (flags & BDRV_O_RDWR) == 0;
/*
* Clear flags that are internal to the block layer before opening the
* image.
@ -472,6 +471,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
goto free_and_fail;
}
bs->keep_read_only = bs->read_only = !(open_flags & BDRV_O_RDWR);
if (drv->bdrv_getlength) {
bs->total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
}
@ -488,13 +488,22 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
filename, bs->backing_file);
if (bs->backing_format[0] != '\0')
back_drv = bdrv_find_format(bs->backing_format);
/* backing files always opened read-only */
open_flags &= ~BDRV_O_RDWR;
ret = bdrv_open2(bs->backing_hd, backing_filename, open_flags,
back_drv);
bs->backing_hd->read_only = (open_flags & BDRV_O_RDWR) == 0;
if (ret < 0) {
bdrv_close(bs);
return ret;
}
if (bs->is_temporary) {
bs->backing_hd->keep_read_only = !(flags & BDRV_O_RDWR);
} else {
/* base image inherits from "parent" */
bs->backing_hd->keep_read_only = bs->keep_read_only;
}
}
if (!bdrv_key_required(bs)) {
@ -570,19 +579,48 @@ int bdrv_commit(BlockDriverState *bs)
{
BlockDriver *drv = bs->drv;
int64_t i, total_sectors;
int n, j;
int ret = 0;
int n, j, ro, open_flags;
int ret = 0, rw_ret = 0;
unsigned char sector[512];
char filename[1024];
BlockDriverState *bs_rw, *bs_ro;
if (!drv)
return -ENOMEDIUM;
if (bs->read_only) {
return -EACCES;
if (!bs->backing_hd) {
return -ENOTSUP;
}
if (!bs->backing_hd) {
return -ENOTSUP;
if (bs->backing_hd->keep_read_only) {
return -EACCES;
}
ro = bs->backing_hd->read_only;
strncpy(filename, bs->backing_hd->filename, sizeof(filename));
open_flags = bs->backing_hd->open_flags;
if (ro) {
/* re-open as RW */
bdrv_delete(bs->backing_hd);
bs->backing_hd = NULL;
bs_rw = bdrv_new("");
rw_ret = bdrv_open2(bs_rw, filename, open_flags | BDRV_O_RDWR, NULL);
if (rw_ret < 0) {
bdrv_delete(bs_rw);
/* try to re-open read-only */
bs_ro = bdrv_new("");
ret = bdrv_open2(bs_ro, filename, open_flags & ~BDRV_O_RDWR, NULL);
if (ret < 0) {
bdrv_delete(bs_ro);
/* drive not functional anymore */
bs->drv = NULL;
return ret;
}
bs->backing_hd = bs_ro;
return rw_ret;
}
bs->backing_hd = bs_rw;
}
total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
@ -590,11 +628,13 @@ int bdrv_commit(BlockDriverState *bs)
if (drv->bdrv_is_allocated(bs, i, 65536, &n)) {
for(j = 0; j < n; j++) {
if (bdrv_read(bs, i, sector, 1) != 0) {
return -EIO;
ret = -EIO;
goto ro_cleanup;
}
if (bdrv_write(bs->backing_hd, i, sector, 1) != 0) {
return -EIO;
ret = -EIO;
goto ro_cleanup;
}
i++;
}
@ -614,6 +654,25 @@ int bdrv_commit(BlockDriverState *bs)
*/
if (bs->backing_hd)
bdrv_flush(bs->backing_hd);
ro_cleanup:
if (ro) {
/* re-open as RO */
bdrv_delete(bs->backing_hd);
bs->backing_hd = NULL;
bs_ro = bdrv_new("");
ret = bdrv_open2(bs_ro, filename, open_flags & ~BDRV_O_RDWR, NULL);
if (ret < 0) {
bdrv_delete(bs_ro);
/* drive not functional anymore */
bs->drv = NULL;
return ret;
}
bs->backing_hd = bs_ro;
bs->backing_hd->keep_read_only = 0;
}
return ret;
}

2
block_int.h
View File

@ -130,6 +130,8 @@ struct BlockDriverState {
int64_t total_sectors; /* if we are reading a disk image, give its
size in sectors */
int read_only; /* if true, the media is read only */
int keep_read_only; /* if true, the media was requested to stay read only */
int open_flags; /* flags used to open the file, re-used for re-open */
int removable; /* if true, the media can be removed */
int locked; /* if true, the media cannot temporarily be ejected */
int encrypted; /* if true, the media is encrypted */