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authorEric Blake <eblake@redhat.com>2016-06-23 16:37:21 -0600
committerKevin Wolf <kwolf@redhat.com>2016-07-05 16:46:25 +0200
commitb9f7855a50a7cbf04454fa84e9d1f333151f2259 (patch)
tree15fa9cfcfab14eccc0eaa76dc3ec56ee22c27a06
parent29cc6a6834add5cddbc391d07c1b3ace2ad9b8eb (diff)
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block: Switch discard length bounds to byte-based
Sector-based limits are awkward to think about; in our on-going quest to move to byte-based interfaces, convert max_discard and discard_alignment. Rename them, using 'pdiscard' as an aid to track which remaining discard interfaces need conversion, and so that the compiler will help us catch the change in semantics across any rebased code. The BlockLimits type is now completely byte-based; and in iscsi.c, sector_limits_lun2qemu() is no longer needed. pdiscard_alignment is made unsigned (we use power-of-2 alignments as bitmasks, where unsigned is easier to think about) while leaving max_pdiscard signed (since we still have an 'int' interface); this is comparable to what commit cf081fc did for write zeroes limits. We may later want to make everything an unsigned 64-bit limit - but that requires a bigger code audit. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/io.c16
-rw-r--r--block/iscsi.c19
-rw-r--r--block/nbd.c2
-rw-r--r--include/block/block_int.h16
-rw-r--r--qemu-img.c3
5 files changed, 29 insertions, 27 deletions
diff --git a/block/io.c b/block/io.c
index 8ca9d43..0f15d05 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2368,19 +2368,21 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
goto out;
}
- max_discard = MIN_NON_ZERO(bs->bl.max_discard, BDRV_REQUEST_MAX_SECTORS);
+ max_discard = MIN_NON_ZERO(bs->bl.max_pdiscard >> BDRV_SECTOR_BITS,
+ BDRV_REQUEST_MAX_SECTORS);
while (nb_sectors > 0) {
int ret;
int num = nb_sectors;
+ int discard_alignment = bs->bl.pdiscard_alignment >> BDRV_SECTOR_BITS;
/* align request */
- if (bs->bl.discard_alignment &&
- num >= bs->bl.discard_alignment &&
- sector_num % bs->bl.discard_alignment) {
- if (num > bs->bl.discard_alignment) {
- num = bs->bl.discard_alignment;
+ if (discard_alignment &&
+ num >= discard_alignment &&
+ sector_num % discard_alignment) {
+ if (num > discard_alignment) {
+ num = discard_alignment;
}
- num -= sector_num % bs->bl.discard_alignment;
+ num -= sector_num % discard_alignment;
}
/* limit request size */
diff --git a/block/iscsi.c b/block/iscsi.c
index bde4a04..342f6b8 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1697,13 +1697,6 @@ static void iscsi_close(BlockDriverState *bs)
memset(iscsilun, 0, sizeof(IscsiLun));
}
-static int sector_limits_lun2qemu(int64_t sector, IscsiLun *iscsilun)
-{
- int limit = MIN(sector_lun2qemu(sector, iscsilun), INT_MAX / 2 + 1);
-
- return limit < BDRV_REQUEST_MAX_SECTORS ? limit : 0;
-}
-
static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
{
/* We don't actually refresh here, but just return data queried in
@@ -1723,14 +1716,14 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
}
if (iscsilun->lbp.lbpu) {
- if (iscsilun->bl.max_unmap < 0xffffffff) {
- bs->bl.max_discard =
- sector_limits_lun2qemu(iscsilun->bl.max_unmap, iscsilun);
+ if (iscsilun->bl.max_unmap < 0xffffffff / iscsilun->block_size) {
+ bs->bl.max_pdiscard =
+ iscsilun->bl.max_unmap * iscsilun->block_size;
}
- bs->bl.discard_alignment =
- sector_limits_lun2qemu(iscsilun->bl.opt_unmap_gran, iscsilun);
+ bs->bl.pdiscard_alignment =
+ iscsilun->bl.opt_unmap_gran * iscsilun->block_size;
} else {
- bs->bl.discard_alignment = iscsilun->block_size >> BDRV_SECTOR_BITS;
+ bs->bl.pdiscard_alignment = iscsilun->block_size;
}
if (iscsilun->bl.max_ws_len < 0xffffffff / iscsilun->block_size) {
diff --git a/block/nbd.c b/block/nbd.c
index f5511ea..08e5b67 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -362,7 +362,7 @@ static int nbd_co_flush(BlockDriverState *bs)
static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)
{
- bs->bl.max_discard = NBD_MAX_SECTORS;
+ bs->bl.max_pdiscard = NBD_MAX_BUFFER_SIZE;
bs->bl.max_transfer = NBD_MAX_BUFFER_SIZE;
}
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 7a4a00f..a3e69fd 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -324,11 +324,17 @@ struct BlockDriver {
};
typedef struct BlockLimits {
- /* maximum number of sectors that can be discarded at once */
- int max_discard;
-
- /* optimal alignment for discard requests in sectors */
- int64_t discard_alignment;
+ /* maximum number of bytes that can be discarded at once (since it
+ * is signed, it must be < 2G, if set), should be multiple of
+ * pdiscard_alignment, but need not be power of 2. May be 0 if no
+ * inherent 32-bit limit */
+ int32_t max_pdiscard;
+
+ /* optimal alignment for discard requests in bytes, must be power
+ * of 2, less than max_pdiscard if that is set, and multiple of
+ * bs->request_alignment. May be 0 if bs->request_alignment is
+ * good enough */
+ uint32_t pdiscard_alignment;
/* maximum number of bytes that can zeroized at once (since it is
* signed, it must be < 2G, if set), should be multiple of
diff --git a/qemu-img.c b/qemu-img.c
index 046b267..3a7c162 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2091,7 +2091,8 @@ static int img_convert(int argc, char **argv)
bufsectors = MIN(32768,
MAX(bufsectors,
MAX(out_bs->bl.opt_transfer >> BDRV_SECTOR_BITS,
- out_bs->bl.discard_alignment)));
+ out_bs->bl.pdiscard_alignment >>
+ BDRV_SECTOR_BITS)));
if (skip_create) {
int64_t output_sectors = blk_nb_sectors(out_blk);