Blame SOURCES/kvm-qemu-img-round-down-request-length-to-an-aligned-sec.patch.patch

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From 070f95bad47e0d0f1884b93184369b3c9322cd4c Mon Sep 17 00:00:00 2001
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Message-Id: <070f95bad47e0d0f1884b93184369b3c9322cd4c.1389014116.git.minovotn@redhat.com>
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In-Reply-To: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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References: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 9 Dec 2013 14:09:37 +0100
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Subject: [PATCH 49/50] qemu-img: round down request length to an aligned
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 sector
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <1386598178-11845-52-git-send-email-pbonzini@redhat.com>
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Patchwork-id: 56088
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O-Subject: [RHEL 7.0 qemu-kvm PATCH 51/52] qemu-img: round down request length to an aligned sector
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Bugzilla: 1039557
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Peter Lieven <pl@kamp.de>
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this patch shortens requests to end at an aligned sector so that
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the next request starts aligned.
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[Squashed Peter's fix for bdrv_get_info() failure discussed on the
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mailing list.
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--Stefan]
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Peter Lieven <pl@kamp.de>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 24f833cd43dbfb5f8ae99e8a6d3691671622d3ea)
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---
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 qemu-img.c | 32 ++++++++++++++++++++++++--------
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 1 file changed, 24 insertions(+), 8 deletions(-)
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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 qemu-img.c | 32 ++++++++++++++++++++++++--------
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 1 file changed, 24 insertions(+), 8 deletions(-)
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diff --git a/qemu-img.c b/qemu-img.c
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index 6890bb1..55bb82c 100644
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--- a/qemu-img.c
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+++ b/qemu-img.c
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@@ -1122,8 +1122,7 @@ out3:
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 static int img_convert(int argc, char **argv)
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 {
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-    int c, n, n1, bs_n, bs_i, compress, cluster_size,
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-        cluster_sectors, skip_create;
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+    int c, n, n1, bs_n, bs_i, compress, cluster_sectors, skip_create;
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     int64_t ret = 0;
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     int progress = 0, flags;
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     const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
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@@ -1395,19 +1394,23 @@ static int img_convert(int argc, char **argv)
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         }
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     }
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-    if (compress) {
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-        ret = bdrv_get_info(out_bs, &bdi;;
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-        if (ret < 0) {
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+    cluster_sectors = 0;
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+    ret = bdrv_get_info(out_bs, &bdi;;
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+    if (ret < 0) {
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+        if (compress) {
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             error_report("could not get block driver info");
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             goto out;
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         }
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-        cluster_size = bdi.cluster_size;
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-        if (cluster_size <= 0 || cluster_size > bufsectors * BDRV_SECTOR_SIZE) {
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+    } else {
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+        cluster_sectors = bdi.cluster_size / BDRV_SECTOR_SIZE;
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+    }
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+
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+    if (compress) {
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+        if (cluster_sectors <= 0 || cluster_sectors > bufsectors) {
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             error_report("invalid cluster size");
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             ret = -1;
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             goto out;
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         }
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-        cluster_sectors = cluster_size >> 9;
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         sector_num = 0;
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         nb_sectors = total_sectors;
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@@ -1540,6 +1543,19 @@ static int img_convert(int argc, char **argv)
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             }
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             n = MIN(nb_sectors, bufsectors);
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+
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+            /* round down request length to an aligned sector, but
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+             * do not bother doing this on short requests. They happen
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+             * when we found an all-zero area, and the next sector to
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+             * write will not be sector_num + n. */
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+            if (cluster_sectors > 0 && n >= cluster_sectors) {
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+                int64_t next_aligned_sector = (sector_num + n);
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+                next_aligned_sector -= next_aligned_sector % cluster_sectors;
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+                if (sector_num + n > next_aligned_sector) {
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+                    n = next_aligned_sector - sector_num;
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+                }
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+            }
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+
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             n = MIN(n, bs_sectors - (sector_num - bs_offset));
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             n1 = n;
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-- 
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1.7.11.7
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