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authorEric Blake <eblake@redhat.com>2016-09-07 16:27:20 -0500
committerPaolo Bonzini <pbonzini@redhat.com>2016-09-22 20:20:51 +0200
commit95eaa78537c734fa3cb3373d47ba8c0099a36ff0 (patch)
treea020b649338485f4d8fe0bae001d472c3e74ce14 /block
parentf8d9ccf8d5f9f4b7d364100871c4c7303b546de5 (diff)
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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>
Diffstat (limited to 'block')
-rw-r--r--block/iscsi.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/block/iscsi.c b/block/iscsi.c
index 95ce9e1..b2b4e5d 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -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);
}