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Blame 0008-hw-9pfs-replace-iovec-manipulation-with-QEMUIOVector.patch

Justin M. Forbes 45e84a
From 45d6cdff48356dc8974497ec0524f971b646dd70 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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Date: Wed, 21 Dec 2011 12:37:22 +0530
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Subject: [PATCH 08/25] hw/9pfs: replace iovec manipulation with QEMUIOVector
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The v9fs_read() and v9fs_write() functions rely on iovec[] manipulation
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code should be replaced with QEMUIOVector to avoid duplicating code.
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In the future it may be possible to make the code even more concise by
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using QEMUIOVector consistently across virtio and 9pfs.
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The "v" format specifier for pdu_marshal() and pdu_unmarshal() is
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dropped since it does not actually pack/unpack anything.  The specifier
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was also not implemented to update the offset variable and could only be
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used at the end of a format string, another sign that this shouldn't
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really be a format specifier.  Instead, see the new
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v9fs_init_qiov_from_pdu() function.
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This change avoids a possible iovec[] buffer overflow when indirect
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vrings are used since the number of vectors is now limited by the
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underlying VirtQueueElement and cannot be out-of-bounds.
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Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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---
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 hw/9pfs/virtio-9p.c |  162 +++++++++++++++++++--------------------------------
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 1 files changed, 60 insertions(+), 102 deletions(-)
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diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
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index dd43209..c018916 100644
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--- a/hw/9pfs/virtio-9p.c
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+++ b/hw/9pfs/virtio-9p.c
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@@ -674,40 +674,6 @@ static size_t pdu_pack(V9fsPDU *pdu, size_t offset, const void *src,
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                              offset, size, 1);
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 }
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-static int pdu_copy_sg(V9fsPDU *pdu, size_t offset, int rx, struct iovec *sg)
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-{
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-    size_t pos = 0;
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-    int i, j;
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-    struct iovec *src_sg;
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-    unsigned int num;
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-
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-    if (rx) {
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-        src_sg = pdu->elem.in_sg;
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-        num = pdu->elem.in_num;
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-    } else {
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-        src_sg = pdu->elem.out_sg;
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-        num = pdu->elem.out_num;
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-    }
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-
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-    j = 0;
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-    for (i = 0; i < num; i++) {
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-        if (offset <= pos) {
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-            sg[j].iov_base = src_sg[i].iov_base;
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-            sg[j].iov_len = src_sg[i].iov_len;
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-            j++;
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-        } else if (offset < (src_sg[i].iov_len + pos)) {
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-            sg[j].iov_base = src_sg[i].iov_base;
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-            sg[j].iov_len = src_sg[i].iov_len;
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-            sg[j].iov_base += (offset - pos);
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-            sg[j].iov_len -= (offset - pos);
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-            j++;
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-        }
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-        pos += src_sg[i].iov_len;
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-    }
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-
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-    return j;
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-}
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-
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 static size_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
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 {
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     size_t old_offset = offset;
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@@ -743,12 +709,6 @@ static size_t pdu_unmarshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
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             *valp = le64_to_cpu(val);
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             break;
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         }
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-        case 'v': {
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-            struct iovec *iov = va_arg(ap, struct iovec *);
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-            int *iovcnt = va_arg(ap, int *);
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-            *iovcnt = pdu_copy_sg(pdu, offset, 0, iov);
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-            break;
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-        }
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         case 's': {
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             V9fsString *str = va_arg(ap, V9fsString *);
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             offset += pdu_unmarshal(pdu, offset, "w", &str->size);
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@@ -827,12 +787,6 @@ static size_t pdu_marshal(V9fsPDU *pdu, size_t offset, const char *fmt, ...)
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             offset += pdu_pack(pdu, offset, &val, sizeof(val));
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             break;
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         }
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-        case 'v': {
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-            struct iovec *iov = va_arg(ap, struct iovec *);
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-            int *iovcnt = va_arg(ap, int *);
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-            *iovcnt = pdu_copy_sg(pdu, offset, 1, iov);
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-            break;
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-        }
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         case 's': {
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             V9fsString *str = va_arg(ap, V9fsString *);
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             offset += pdu_marshal(pdu, offset, "w", str->size);
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@@ -1143,42 +1097,6 @@ static void stat_to_v9stat_dotl(V9fsState *s, const struct stat *stbuf,
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     stat_to_qid(stbuf, &v9lstat->qid);
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 }
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-static struct iovec *adjust_sg(struct iovec *sg, int len, int *iovcnt)
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-{
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-    while (len && *iovcnt) {
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-        if (len < sg->iov_len) {
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-            sg->iov_len -= len;
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-            sg->iov_base += len;
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-            len = 0;
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-        } else {
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-            len -= sg->iov_len;
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-            sg++;
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-            *iovcnt -= 1;
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-        }
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-    }
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-
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-    return sg;
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-}
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-
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-static struct iovec *cap_sg(struct iovec *sg, int cap, int *cnt)
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-{
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-    int i;
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-    int total = 0;
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-
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-    for (i = 0; i < *cnt; i++) {
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-        if ((total + sg[i].iov_len) > cap) {
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-            sg[i].iov_len -= ((total + sg[i].iov_len) - cap);
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-            i++;
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-            break;
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-        }
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-        total += sg[i].iov_len;
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-    }
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-
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-    *cnt = i;
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-
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-    return sg;
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-}
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-
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 static void print_sg(struct iovec *sg, int cnt)
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 {
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     int i;
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@@ -1861,6 +1779,38 @@ out:
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     return count;
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 }
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+/*
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+ * Create a QEMUIOVector for a sub-region of PDU iovecs
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+ *
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+ * @qiov:       uninitialized QEMUIOVector
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+ * @skip:       number of bytes to skip from beginning of PDU
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+ * @size:       number of bytes to include
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+ * @is_write:   true - write, false - read
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+ *
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+ * The resulting QEMUIOVector has heap-allocated iovecs and must be cleaned up
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+ * with qemu_iovec_destroy().
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+ */
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+static void v9fs_init_qiov_from_pdu(QEMUIOVector *qiov, V9fsPDU *pdu,
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+                                    uint64_t skip, size_t size,
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+                                    bool is_write)
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+{
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+    QEMUIOVector elem;
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+    struct iovec *iov;
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+    unsigned int niov;
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+
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+    if (is_write) {
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+        iov = pdu->elem.out_sg;
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+        niov = pdu->elem.out_num;
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+    } else {
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+        iov = pdu->elem.in_sg;
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+        niov = pdu->elem.in_num;
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+    }
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+
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+    qemu_iovec_init_external(&elem, iov, niov);
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+    qemu_iovec_init(qiov, niov);
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+    qemu_iovec_copy(qiov, &elem, skip, size);
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+}
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+
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 static void v9fs_read(void *opaque)
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 {
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     int32_t fid;
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@@ -1895,21 +1845,21 @@ static void v9fs_read(void *opaque)
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         err += pdu_marshal(pdu, offset, "d", count);
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         err += count;
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     } else if (fidp->fid_type == P9_FID_FILE) {
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-        int32_t cnt;
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+        QEMUIOVector qiov_full;
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+        QEMUIOVector qiov;
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         int32_t len;
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-        struct iovec *sg;
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-        struct iovec iov[128]; /* FIXME: bad, bad, bad */
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-        sg = iov;
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-        pdu_marshal(pdu, offset + 4, "v", sg, &cnt);
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-        sg = cap_sg(sg, max_count, &cnt);
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+        v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset + 4, max_count, false);
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+        qemu_iovec_init(&qiov, qiov_full.niov);
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         do {
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+            qemu_iovec_reset(&qiov);
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+            qemu_iovec_copy(&qiov, &qiov_full, count, qiov_full.size - count);
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             if (0) {
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-                print_sg(sg, cnt);
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+                print_sg(qiov.iov, qiov.niov);
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             }
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             /* Loop in case of EINTR */
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             do {
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-                len = v9fs_co_preadv(pdu, fidp, sg, cnt, off);
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+                len = v9fs_co_preadv(pdu, fidp, qiov.iov, qiov.niov, off);
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                 if (len >= 0) {
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                     off   += len;
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                     count += len;
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@@ -1920,11 +1870,12 @@ static void v9fs_read(void *opaque)
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                 err = len;
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                 goto out;
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             }
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-            sg = adjust_sg(sg, len, &cnt);
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         } while (count < max_count && len > 0);
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         err = offset;
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         err += pdu_marshal(pdu, offset, "d", count);
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         err += count;
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+        qemu_iovec_destroy(&qiov);
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+        qemu_iovec_destroy(&qiov_full);
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     } else if (fidp->fid_type == P9_FID_XATTR) {
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         err = v9fs_xattr_read(s, pdu, fidp, off, max_count);
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     } else {
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@@ -2095,7 +2046,6 @@ out:
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 static void v9fs_write(void *opaque)
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 {
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-    int cnt;
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     ssize_t err;
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     int32_t fid;
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     int64_t off;
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@@ -2104,13 +2054,14 @@ static void v9fs_write(void *opaque)
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     int32_t total = 0;
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     size_t offset = 7;
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     V9fsFidState *fidp;
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-    struct iovec iov[128]; /* FIXME: bad, bad, bad */
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-    struct iovec *sg = iov;
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     V9fsPDU *pdu = opaque;
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     V9fsState *s = pdu->s;
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+    QEMUIOVector qiov_full;
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+    QEMUIOVector qiov;
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-    pdu_unmarshal(pdu, offset, "dqdv", &fid, &off, &count, sg, &cnt);
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-    trace_v9fs_write(pdu->tag, pdu->id, fid, off, count, cnt);
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+    offset += pdu_unmarshal(pdu, offset, "dqd", &fid, &off, &count);
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+    v9fs_init_qiov_from_pdu(&qiov_full, pdu, offset, count, true);
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+    trace_v9fs_write(pdu->tag, pdu->id, fid, off, count, qiov_full.niov);
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     fidp = get_fid(pdu, fid);
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     if (fidp == NULL) {
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@@ -2126,20 +2077,23 @@ static void v9fs_write(void *opaque)
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         /*
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          * setxattr operation
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          */
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-        err = v9fs_xattr_write(s, pdu, fidp, off, count, sg, cnt);
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+        err = v9fs_xattr_write(s, pdu, fidp, off, count,
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+                               qiov_full.iov, qiov_full.niov);
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         goto out;
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     } else {
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         err = -EINVAL;
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         goto out;
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     }
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-    sg = cap_sg(sg, count, &cnt);
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+    qemu_iovec_init(&qiov, qiov_full.niov);
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     do {
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+        qemu_iovec_reset(&qiov);
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+        qemu_iovec_copy(&qiov, &qiov_full, total, qiov_full.size - total);
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         if (0) {
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-            print_sg(sg, cnt);
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+            print_sg(qiov.iov, qiov.niov);
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         }
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         /* Loop in case of EINTR */
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         do {
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-            len = v9fs_co_pwritev(pdu, fidp, sg, cnt, off);
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+            len = v9fs_co_pwritev(pdu, fidp, qiov.iov, qiov.niov, off);
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             if (len >= 0) {
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                 off   += len;
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                 total += len;
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@@ -2148,16 +2102,20 @@ static void v9fs_write(void *opaque)
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         if (len < 0) {
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             /* IO error return the error */
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             err = len;
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-            goto out;
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+            goto out_qiov;
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         }
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-        sg = adjust_sg(sg, len, &cnt);
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     } while (total < count && len > 0);
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+
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+    offset = 7;
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     offset += pdu_marshal(pdu, offset, "d", total);
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     err = offset;
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     trace_v9fs_write_return(pdu->tag, pdu->id, total, err);
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+out_qiov:
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+    qemu_iovec_destroy(&qiov);
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 out:
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     put_fid(pdu, fidp);
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 out_nofid:
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+    qemu_iovec_destroy(&qiov_full);
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     complete_pdu(s, pdu, err);
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 }
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-- 
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1.7.7.5
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