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From ea0e0a4820d0dfa1227bd8351d89e9d55b25da44 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue, 17 Mar 2015 12:59:01 +0100
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Subject: [PATCH 12/16] raw-posix: Fail gracefully if no working alignment is
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 found
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Message-id: <1424365599-9801-3-git-send-email-stefanha@redhat.com>
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Patchwork-id: 63913
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O-Subject: [RHEL-7.1 qemu-kvm PATCH 2/2] raw-posix: Fail gracefully if no working alignment is found
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Bugzilla: 1184363
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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From: Kevin Wolf <kwolf@redhat.com>
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If qemu couldn't find out what O_DIRECT alignment to use with a given
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file, it would run into assert(bdrv_opt_mem_align(bs) != 0); in block.c
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and confuse users. This adds a more descriptive error message for such
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cases.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit df26a35025427f34c1d4e5a8e51152371a5e231e)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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 block/raw-posix.c | 35 +++++++++++++++++++++++++++--------
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 1 file changed, 27 insertions(+), 8 deletions(-)
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diff --git a/block/raw-posix.c b/block/raw-posix.c
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index 6a50856..af526ca 100644
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--- a/block/raw-posix.c
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+++ b/block/raw-posix.c
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@@ -213,7 +213,7 @@ static int raw_normalize_devicepath(const char **filename)
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 }
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 #endif
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-static void raw_probe_alignment(BlockDriverState *bs)
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+static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
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 {
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     BDRVRawState *s = bs->opaque;
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     char *buf;
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@@ -232,24 +232,24 @@ static void raw_probe_alignment(BlockDriverState *bs)
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     s->buf_align = 0;
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 #ifdef BLKSSZGET
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-    if (ioctl(s->fd, BLKSSZGET, &sector_size) >= 0) {
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+    if (ioctl(fd, BLKSSZGET, &sector_size) >= 0) {
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         bs->request_alignment = sector_size;
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     }
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 #endif
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 #ifdef DKIOCGETBLOCKSIZE
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-    if (ioctl(s->fd, DKIOCGETBLOCKSIZE, &sector_size) >= 0) {
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+    if (ioctl(fd, DKIOCGETBLOCKSIZE, &sector_size) >= 0) {
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         bs->request_alignment = sector_size;
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     }
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 #endif
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 #ifdef DIOCGSECTORSIZE
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-    if (ioctl(s->fd, DIOCGSECTORSIZE, &sector_size) >= 0) {
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+    if (ioctl(fd, DIOCGSECTORSIZE, &sector_size) >= 0) {
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         bs->request_alignment = sector_size;
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     }
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 #endif
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 #ifdef CONFIG_XFS
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     if (s->is_xfs) {
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         struct dioattr da;
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-        if (xfsctl(NULL, s->fd, XFS_IOC_DIOINFO, &da) >= 0) {
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+        if (xfsctl(NULL, fd, XFS_IOC_DIOINFO, &da) >= 0) {
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             bs->request_alignment = da.d_miniosz;
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             /* The kernel returns wrong information for d_mem */
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             /* s->buf_align = da.d_mem; */
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@@ -262,7 +262,7 @@ static void raw_probe_alignment(BlockDriverState *bs)
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         size_t align;
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         buf = qemu_memalign(MAX_BLOCKSIZE, 2 * MAX_BLOCKSIZE);
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         for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
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-            if (pread(s->fd, buf + align, MAX_BLOCKSIZE, 0) >= 0) {
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+            if (pread(fd, buf + align, MAX_BLOCKSIZE, 0) >= 0) {
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                 s->buf_align = align;
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                 break;
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             }
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@@ -274,13 +274,18 @@ static void raw_probe_alignment(BlockDriverState *bs)
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         size_t align;
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         buf = qemu_memalign(s->buf_align, MAX_BLOCKSIZE);
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         for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
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-            if (pread(s->fd, buf, align, 0) >= 0) {
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+            if (pread(fd, buf, align, 0) >= 0) {
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                 bs->request_alignment = align;
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                 break;
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             }
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         }
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         qemu_vfree(buf);
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     }
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+
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+    if (!s->buf_align || !bs->request_alignment) {
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+        error_setg(errp, "Could not find working O_DIRECT alignment. "
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+                         "Try cache.direct=off.");
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+    }
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 }
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 static void raw_parse_flags(int bdrv_flags, int *open_flags)
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@@ -459,6 +464,7 @@ static int raw_reopen_prepare(BDRVReopenState *state,
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     BDRVRawState *s;
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     BDRVRawReopenState *raw_s;
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     int ret = 0;
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+    Error *local_err = NULL;
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     assert(state != NULL);
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     assert(state->bs != NULL);
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@@ -531,6 +537,19 @@ static int raw_reopen_prepare(BDRVReopenState *state,
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             ret = -1;
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         }
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     }
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+
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+    /* Fail already reopen_prepare() if we can't get a working O_DIRECT
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+     * alignment with the new fd. */
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+    if (raw_s->fd != -1) {
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+        raw_probe_alignment(state->bs, raw_s->fd, &local_err);
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+        if (local_err) {
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+            qemu_close(raw_s->fd);
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+            raw_s->fd = -1;
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+            error_propagate(errp, local_err);
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+            ret = -EINVAL;
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+        }
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+    }
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+
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     return ret;
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 }
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@@ -573,7 +592,7 @@ static int raw_refresh_limits(BlockDriverState *bs)
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 {
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     BDRVRawState *s = bs->opaque;
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-    raw_probe_alignment(bs);
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+    raw_probe_alignment(bs, s->fd, errp);
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     bs->bl.opt_mem_alignment = s->buf_align;
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     return 0;
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-- 
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1.8.3.1
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