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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 5/6] tools/libxl: Extend datacopier to support reading into a buffer
Currently a datacopier may source its data from an fd or local buffer, but its
destination must be an fd. For migration v2, libxl needs to read from the
migration stream into a local buffer.
Implement a "read into local buffer" mode, invoked when readbuf is set and
writefd is -1. On success, the callback passes the number of bytes read.
Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
[Rewrite commit message]
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
---
tools/libxl/libxl_aoutils.c | 59 +++++++++++++++++++++++++++-----------------
tools/libxl/libxl_internal.h | 8 ++++--
2 files changed, 42 insertions(+), 25 deletions(-)
diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index dff5d71..a5a10fb 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -134,7 +134,7 @@ static void datacopier_check_state(libxl__egc *egc,
libxl__datacopier_state *dc)
STATE_AO_GC(dc->ao);
int rc;
- if (dc->used) {
+ if (dc->used && !dc->readbuf) {
if (!libxl__ev_fd_isregistered(&dc->towrite)) {
rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
dc->writefd, POLLOUT);
@@ -148,7 +148,7 @@ static void datacopier_check_state(libxl__egc *egc,
libxl__datacopier_state *dc)
} else if (!libxl__ev_fd_isregistered(&dc->toread) ||
dc->bytes_to_read == 0) {
/* we have had eof */
- datacopier_callback(egc, dc, 0, 0);
+ datacopier_callback(egc, dc, 0, dc->readbuf ? dc->used : 0);
return;
} else {
/* nothing buffered, but still reading */
@@ -216,25 +216,31 @@ static void datacopier_readable(libxl__egc *egc,
libxl__ev_fd *ev,
}
assert(revents & POLLIN);
for (;;) {
- while (dc->used >= dc->maxsz) {
- libxl__datacopier_buf *rm = LIBXL_TAILQ_FIRST(&dc->bufs);
- dc->used -= rm->used;
- assert(dc->used >= 0);
- LIBXL_TAILQ_REMOVE(&dc->bufs, rm, entry);
- free(rm);
- }
+ libxl__datacopier_buf *buf = NULL;
+ int r;
+
+ if (dc->readbuf) {
+ r = read(ev->fd, dc->readbuf + dc->used, dc->bytes_to_read);
+ } else {
+ while (dc->used >= dc->maxsz) {
+ libxl__datacopier_buf *rm = LIBXL_TAILQ_FIRST(&dc->bufs);
+ dc->used -= rm->used;
+ assert(dc->used >= 0);
+ LIBXL_TAILQ_REMOVE(&dc->bufs, rm, entry);
+ free(rm);
+ }
- libxl__datacopier_buf *buf =
- LIBXL_TAILQ_LAST(&dc->bufs, libxl__datacopier_bufs);
- if (!buf || buf->used >= sizeof(buf->buf)) {
- buf = malloc(sizeof(*buf));
- if (!buf) libxl__alloc_failed(CTX, __func__, 1, sizeof(*buf));
- buf->used = 0;
- LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
- }
- int r = read(ev->fd, buf->buf + buf->used,
+ buf = LIBXL_TAILQ_LAST(&dc->bufs, libxl__datacopier_bufs);
+ if (!buf || buf->used >= sizeof(buf->buf)) {
+ buf = malloc(sizeof(*buf));
+ if (!buf) libxl__alloc_failed(CTX, __func__, 1, sizeof(*buf));
+ buf->used = 0;
+ LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
+ }
+ r = read(ev->fd, buf->buf + buf->used,
min_t(size_t, sizeof(buf->buf) - buf->used,
(dc->bytes_to_read == -1) ? SIZE_MAX :
dc->bytes_to_read));
+ }
if (r < 0) {
if (errno == EINTR) continue;
if (errno == EWOULDBLOCK) break;
@@ -257,9 +263,11 @@ static void datacopier_readable(libxl__egc *egc,
libxl__ev_fd *ev,
return;
}
}
- buf->used += r;
+ if (!dc->readbuf) {
+ buf->used += r;
+ assert(buf->used <= sizeof(buf->buf));
+ }
dc->used += r;
- assert(buf->used <= sizeof(buf->buf));
if (dc->bytes_to_read > 0)
dc->bytes_to_read -= r;
if (dc->bytes_to_read == 0)
@@ -318,15 +326,20 @@ int libxl__datacopier_start(libxl__datacopier_state *dc)
libxl__datacopier_init(dc);
+ assert(dc->readfd >= 0 || dc->writefd >= 0);
+ assert(!(dc->readbuf && dc->bytes_to_read == -1));
+
if (dc->readfd >= 0) {
rc = libxl__ev_fd_register(gc, &dc->toread, datacopier_readable,
dc->readfd, POLLIN);
if (rc) goto out;
}
- rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
- dc->writefd, POLLOUT);
- if (rc) goto out;
+ if (dc->writefd >= 0) {
+ rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
+ dc->writefd, POLLOUT);
+ if (rc) goto out;
+ }
return 0;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 58ac658..931c00c 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2524,8 +2524,9 @@ typedef struct libxl__datacopier_buf
libxl__datacopier_buf;
/* onwrite==1 means failure happened when writing, logged, errnoval is valid
* onwrite==0 means failure happened when reading
- * errnoval==0 means we got eof and all data was written
- * errnoval!=0 means we had a read error, logged
+ * errnoval>=0 means we got eof and all data was written or number of bytes
+ * written when in read mode
+ * errnoval<0 means we had a read error, logged
* onwrite==-1 means some other internal failure, errnoval not valid, logged
* If we get POLLHUP, we call callback_pollhup(..., onwrite, -1);
* or if callback_pollhup==0 this is an internal failure, as above.
@@ -2550,6 +2551,9 @@ struct libxl__datacopier_state {
FILE *log; /* gets a copy of everything */
libxl__datacopier_callback *callback;
libxl__datacopier_callback *callback_pollhup;
+ void *readbuf; /* Set this to read data into it without writing to an
+ fd. The buffer should be at least as large as the
+ bytes_to_read parameter, which should not be -1. */
/* remaining fields are private to datacopier */
libxl__ev_fd toread, towrite;
ssize_t used;
--
2.1.0
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