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block: Separate blk_is_writable() and blk_supports_write_perm()

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Currently, blk_is_read_only() tells whether a given BlockBackend can
only be used in read-only mode because its root node is read-only. Some
callers actually try to answer a slightly different question: Is the
BlockBackend configured to be writable, by taking write permissions on
the root node?

This can differ, for example, for CD-ROM devices which don't take write
permissions, but may be backed by a writable image file. scsi-cd allows
write requests to the drive if blk_is_read_only() returns false.
However, the write request will immediately run into an assertion
failure because the write permission is missing.

This patch introduces separate functions for both questions.
blk_supports_write_perm() answers the question whether the block
node/image file can support writable devices, whereas blk_is_writable()
tells whether the BlockBackend is currently configured to be writable.

All calls of blk_is_read_only() are converted to one of the two new
functions.

Fixes: https://bugs.launchpad.net/bugs/1906693
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210118123448.307825-2-kwolf@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2021-01-18 13:34:47 +01:00
parent bf159f0bdc
commit 86b1cf3227
20 changed files with 57 additions and 41 deletions
Download patch file Download diff file Expand all files Collapse all files

10
hw/scsi/scsi-disk.c
View file

@ -1270,7 +1270,7 @@ static int scsi_disk_emulate_mode_sense(SCSIDiskReq *r, uint8_t *outbuf)
if (s->qdev.type == TYPE_DISK) {
dev_specific_param = s->features & (1 << SCSI_DISK_F_DPOFUA) ? 0x10 : 0;
if (blk_is_read_only(s->qdev.conf.blk)) {
if (!blk_is_writable(s->qdev.conf.blk)) {
dev_specific_param |= 0x80; /* Readonly. */
}
} else {
@ -1704,7 +1704,7 @@ static void scsi_disk_emulate_unmap(SCSIDiskReq *r, uint8_t *inbuf)
goto invalid_param_len;
}
if (blk_is_read_only(s->qdev.conf.blk)) {
if (!blk_is_writable(s->qdev.conf.blk)) {
block_acct_invalid(blk_get_stats(s->qdev.conf.blk), BLOCK_ACCT_UNMAP);
scsi_check_condition(r, SENSE_CODE(WRITE_PROTECTED));
return;
@ -1795,7 +1795,7 @@ static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf)
return;
}
if (blk_is_read_only(s->qdev.conf.blk)) {
if (!blk_is_writable(s->qdev.conf.blk)) {
scsi_check_condition(r, SENSE_CODE(WRITE_PROTECTED));
return;
}
@ -2207,7 +2207,7 @@ static int32_t scsi_disk_dma_command(SCSIRequest *req, uint8_t *buf)
case WRITE_VERIFY_10:
case WRITE_VERIFY_12:
case WRITE_VERIFY_16:
if (blk_is_read_only(s->qdev.conf.blk)) {
if (!blk_is_writable(s->qdev.conf.blk)) {
scsi_check_condition(r, SENSE_CODE(WRITE_PROTECTED));
return 0;
}
@ -2380,7 +2380,7 @@ static void scsi_realize(SCSIDevice *dev, Error **errp)
}
}
read_only = blk_is_read_only(s->qdev.conf.blk);
read_only = !blk_supports_write_perm(s->qdev.conf.blk);
if (dev->type == TYPE_ROM) {
read_only = true;
}