OpenE2K
/
qemu-e2k
13
4
Fork 0
Code Issues 4 Pull Requests Projects 2 Releases Activity

iscsi: Fix divide-by-zero regression on raw SG devices 

When qemu uses iscsi devices in sg mode, iscsilun->block_size
is left at 0.  Prior to commits cf081fca and similar, when
block limits were tracked in sectors, this did not matter:
various block limits were just left at 0.  But when we started
scaling by block size, this caused SIGFPE.

Then, in a later patch, commit a5b8dd2c added an assertion to
bdrv_open_common() that request_alignment is always non-zero;
which was not true for SG mode.  Rather than relax that assertion,
we can just provide a sane value (we don't know of any SG device
with a block size smaller than qemu's default sizing of 512 bytes).

One possible solution for SG mode is to just blindly skip ALL
of iscsi_refresh_limits(), since we already short circuit so
many other things in sg mode.  But this patch takes a slightly
more conservative approach, and merely guarantees that scaling
will succeed, while still using multiples of the original size
where possible.  Resulting limits may still be zero in SG mode
(that is, we mostly only fix block_size used as a denominator
or which affect assertions, not all uses).

Reported-by: Holger Schranz <holger@fam-schranz.de>
Signed-off-by: Eric Blake <eblake@redhat.com>
CC: qemu-stable@nongnu.org

Message-Id: <1473283640-15756-1-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eric Blake 2016-09-07 16:27:20 -05:00 committed by Paolo Bonzini
parent f8d9ccf8d5
commit 95eaa78537
1 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
block/iscsi.c
View File

@ -1813,19 +1813,22 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
IscsiLun *iscsilun = bs->opaque;
uint64_t max_xfer_len = iscsilun->use_16_for_rw ? 0xffffffff : 0xffff;
unsigned int block_size = MAX(BDRV_SECTOR_SIZE, iscsilun->block_size);
bs->bl.request_alignment = iscsilun->block_size;
assert(iscsilun->block_size >= BDRV_SECTOR_SIZE || bs->sg);
bs->bl.request_alignment = block_size;
if (iscsilun->bl.max_xfer_len) {
max_xfer_len = MIN(max_xfer_len, iscsilun->bl.max_xfer_len);
}
if (max_xfer_len * iscsilun->block_size < INT_MAX) {
if (max_xfer_len * block_size < INT_MAX) {
bs->bl.max_transfer = max_xfer_len * iscsilun->block_size;
}
if (iscsilun->lbp.lbpu) {
if (iscsilun->bl.max_unmap < 0xffffffff / iscsilun->block_size) {
if (iscsilun->bl.max_unmap < 0xffffffff / block_size) {
bs->bl.max_pdiscard =
iscsilun->bl.max_unmap * iscsilun->block_size;
}
@ -1835,7 +1838,7 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
bs->bl.pdiscard_alignment = iscsilun->block_size;
}
if (iscsilun->bl.max_ws_len < 0xffffffff / iscsilun->block_size) {
if (iscsilun->bl.max_ws_len < 0xffffffff / block_size) {
bs->bl.max_pwrite_zeroes =
iscsilun->bl.max_ws_len * iscsilun->block_size;
}
@ -1846,7 +1849,7 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
bs->bl.pwrite_zeroes_alignment = iscsilun->block_size;
}
if (iscsilun->bl.opt_xfer_len &&
iscsilun->bl.opt_xfer_len < INT_MAX / iscsilun->block_size) {
iscsilun->bl.opt_xfer_len < INT_MAX / block_size) {
bs->bl.opt_transfer = pow2floor(iscsilun->bl.opt_xfer_len *
iscsilun->block_size);
}