Re: [Qemu-devel] [PATCH v4 01/47] QEMUSizedBuffer based QEMUFile

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

On 2014/10/4 1:47, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> * Please comment on separate thread for this QEMUSizedBuffer patch *
>
> This is based on Stefan and Joel's patch that creates a QEMUFile that goes
> to a memory buffer; from:
>
> http://lists.gnu.org/archive/html/qemu-devel/2013-03/msg05036.html
>
> Using the QEMUFile interface, this patch adds support functions for
> operating on in-memory sized buffers that can be written to or read from.
>
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> Signed-off-by: Joel Schopp <jschopp@linux.vnet.ibm.com>
>
> For fixes/tweeks I've done:
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>   include/migration/qemu-file.h |  28 +++
>   include/qemu/typedefs.h       |   1 +
>   qemu-file.c                   | 456 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 485 insertions(+)
>
> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
> index c90f529..6ef8ebc 100644
> --- a/include/migration/qemu-file.h
> +++ b/include/migration/qemu-file.h
> @@ -25,6 +25,8 @@
>   #define QEMU_FILE_H 1
>   #include "exec/cpu-common.h"
>
> +#include <stdint.h>
> +
>   /* This function writes a chunk of data to a file at the given position.
>    * The pos argument can be ignored if the file is only being used for
>    * streaming.  The handler should try to write all of the data it can.
> @@ -94,11 +96,21 @@ typedef struct QEMUFileOps {
>       QEMURamSaveFunc *save_page;
>   } QEMUFileOps;
>
> +struct QEMUSizedBuffer {
> +    struct iovec *iov;
> +    size_t n_iov;
> +    size_t size; /* total allocated size in all iov's */
> +    size_t used; /* number of used bytes */
> +};
> +
> +typedef struct QEMUSizedBuffer QEMUSizedBuffer;
> +

There is a redefinition of typedef ‘QEMUSizedBuffer’ in
'include/qemu/typedefs.h:68', when i compile qemu, it complains;)


>   QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops);
>   QEMUFile *qemu_fopen(const char *filename, const char *mode);
>   QEMUFile *qemu_fdopen(int fd, const char *mode);
>   QEMUFile *qemu_fopen_socket(int fd, const char *mode);
>   QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
> +QEMUFile *qemu_bufopen(const char *mode, QEMUSizedBuffer *input);
>   int qemu_get_fd(QEMUFile *f);
>   int qemu_fclose(QEMUFile *f);
>   int64_t qemu_ftell(QEMUFile *f);
> @@ -111,6 +123,22 @@ void qemu_put_byte(QEMUFile *f, int v);
>   void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size);
>   bool qemu_file_mode_is_not_valid(const char *mode);
>
> +QEMUSizedBuffer *qsb_create(const uint8_t *buffer, size_t len);
> +QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *);
> +void qsb_free(QEMUSizedBuffer *);
> +size_t qsb_set_length(QEMUSizedBuffer *qsb, size_t length);
> +size_t qsb_get_length(const QEMUSizedBuffer *qsb);
> +ssize_t qsb_get_buffer(const QEMUSizedBuffer *, off_t start, size_t count,
> +                       uint8_t *buf);
> +ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *buf,
> +                     off_t pos, size_t count);
> +
> +
> +/*
> + * For use on files opened with qemu_bufopen
> + */
> +const QEMUSizedBuffer *qemu_buf_get(QEMUFile *f);
> +
>   static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
>   {
>       qemu_put_byte(f, (int)v);
> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> index 5f20b0e..db1153a 100644
> --- a/include/qemu/typedefs.h
> +++ b/include/qemu/typedefs.h
> @@ -60,6 +60,7 @@ typedef struct PCIEAERLog PCIEAERLog;
>   typedef struct PCIEAERErr PCIEAERErr;
>   typedef struct PCIEPort PCIEPort;
>   typedef struct PCIESlot PCIESlot;
> +typedef struct QEMUSizedBuffer QEMUSizedBuffer;

Here!, see above comment. Thanks.

>   typedef struct MSIMessage MSIMessage;
>   typedef struct SerialState SerialState;
>   typedef struct PCMCIACardState PCMCIACardState;
> diff --git a/qemu-file.c b/qemu-file.c
> index a8e3912..ccc516c 100644
> --- a/qemu-file.c
> +++ b/qemu-file.c
> @@ -878,3 +878,459 @@ uint64_t qemu_get_be64(QEMUFile *f)
>       v |= qemu_get_be32(f);
>       return v;
>   }
> +
> +#define QSB_CHUNK_SIZE      (1 << 10)
> +#define QSB_MAX_CHUNK_SIZE  (16 * QSB_CHUNK_SIZE)
> +
> +/**
> + * Create a QEMUSizedBuffer
> + * This type of buffer uses scatter-gather lists internally and
> + * can grow to any size. Any data array in the scatter-gather list
> + * can hold different amount of bytes.
> + *
> + * @buffer: Optional buffer to copy into the QSB
> + * @len: size of initial buffer; if @buffer is given, buffer must
> + *       hold at least len bytes
> + *
> + * Returns a pointer to a QEMUSizedBuffer or NULL on allocation failure
> + */
> +QEMUSizedBuffer *qsb_create(const uint8_t *buffer, size_t len)
> +{
> +    QEMUSizedBuffer *qsb;
> +    size_t alloc_len, num_chunks, i, to_copy;
> +    size_t chunk_size = (len > QSB_MAX_CHUNK_SIZE)
> +                        ? QSB_MAX_CHUNK_SIZE
> +                        : QSB_CHUNK_SIZE;
> +
> +    num_chunks = DIV_ROUND_UP(len ? len : QSB_CHUNK_SIZE, chunk_size);
> +    alloc_len = num_chunks * chunk_size;
> +
> +    qsb = g_try_new0(QEMUSizedBuffer, 1);
> +    if (!qsb) {
> +        return NULL;
> +    }
> +
> +    qsb->iov = g_try_new0(struct iovec, num_chunks);
> +    if (!qsb->iov) {
> +        g_free(qsb);
> +        return NULL;
> +    }
> +
> +    qsb->n_iov = num_chunks;
> +
> +    for (i = 0; i < num_chunks; i++) {
> +        qsb->iov[i].iov_base = g_try_malloc0(chunk_size);
> +        if (!qsb->iov[i].iov_base) {
> +            /* qsb_free is safe since g_free can cope with NULL */
> +            qsb_free(qsb);
> +            return NULL;
> +        }
> +
> +        qsb->iov[i].iov_len = chunk_size;
> +        if (buffer) {
> +            to_copy = (len - qsb->used) > chunk_size
> +                      ? chunk_size : (len - qsb->used);
> +            memcpy(qsb->iov[i].iov_base, &buffer[qsb->used], to_copy);
> +            qsb->used += to_copy;
> +        }
> +    }
> +
> +    qsb->size = alloc_len;
> +
> +    return qsb;
> +}
> +
> +/**
> + * Free the QEMUSizedBuffer
> + *
> + * @qsb: The QEMUSizedBuffer to free
> + */
> +void qsb_free(QEMUSizedBuffer *qsb)
> +{
> +    size_t i;
> +
> +    if (!qsb) {
> +        return;
> +    }
> +
> +    for (i = 0; i < qsb->n_iov; i++) {
> +        g_free(qsb->iov[i].iov_base);
> +    }
> +    g_free(qsb->iov);
> +    g_free(qsb);
> +}
> +
> +/**
> + * Get the number of used bytes in the QEMUSizedBuffer
> + *
> + * @qsb: A QEMUSizedBuffer
> + *
> + * Returns the number of bytes currently used in this buffer
> + */
> +size_t qsb_get_length(const QEMUSizedBuffer *qsb)
> +{
> +    return qsb->used;
> +}
> +
> +/**
> + * Set the length of the buffer; the primary usage of this
> + * function is to truncate the number of used bytes in the buffer.
> + * The size will not be extended beyond the current number of
> + * allocated bytes in the QEMUSizedBuffer.
> + *
> + * @qsb: A QEMUSizedBuffer
> + * @new_len: The new length of bytes in the buffer
> + *
> + * Returns the number of bytes the buffer was truncated or extended
> + * to.
> + */
> +size_t qsb_set_length(QEMUSizedBuffer *qsb, size_t new_len)
> +{
> +    if (new_len <= qsb->size) {
> +        qsb->used = new_len;
> +    } else {
> +        qsb->used = qsb->size;
> +    }
> +    return qsb->used;
> +}
> +
> +/**
> + * Get the iovec that holds the data for a given position @pos.
> + *
> + * @qsb: A QEMUSizedBuffer
> + * @pos: The index of a byte in the buffer
> + * @d_off: Pointer to an offset that this function will indicate
> + *         at what position within the returned iovec the byte
> + *         is to be found
> + *
> + * Returns the index of the iovec that holds the byte at the given
> + * index @pos in the byte stream; a negative number if the iovec
> + * for the given position @pos does not exist.
> + */
> +static ssize_t qsb_get_iovec(const QEMUSizedBuffer *qsb,
> +                             off_t pos, off_t *d_off)
> +{
> +    ssize_t i;
> +    off_t curr = 0;
> +
> +    if (pos > qsb->used) {
> +        return -1;
> +    }
> +
> +    for (i = 0; i < qsb->n_iov; i++) {
> +        if (curr + qsb->iov[i].iov_len > pos) {
> +            *d_off = pos - curr;
> +            return i;
> +        }
> +        curr += qsb->iov[i].iov_len;
> +    }
> +    return -1;
> +}
> +
> +/*
> + * Convert the QEMUSizedBuffer into a flat buffer.
> + *
> + * Note: If at all possible, try to avoid this function since it
> + *       may unnecessarily copy memory around.
> + *
> + * @qsb: pointer to QEMUSizedBuffer
> + * @start: offset to start at
> + * @count: number of bytes to copy
> + * @buf: a pointer to a buffer to write into (at least @count bytes)
> + *
> + * Returns the number of bytes copied into the output buffer
> + */
> +ssize_t qsb_get_buffer(const QEMUSizedBuffer *qsb, off_t start,
> +                       size_t count, uint8_t *buffer)
> +{
> +    const struct iovec *iov;
> +    size_t to_copy, all_copy;
> +    ssize_t index;
> +    off_t s_off;
> +    off_t d_off = 0;
> +    char *s;
> +
> +    if (start > qsb->used) {
> +        return 0;
> +    }
> +
> +    all_copy = qsb->used - start;
> +    if (all_copy > count) {
> +        all_copy = count;
> +    } else {
> +        count = all_copy;
> +    }
> +
> +    index = qsb_get_iovec(qsb, start, &s_off);
> +    if (index < 0) {
> +        return 0;
> +    }
> +
> +    while (all_copy > 0) {
> +        iov = &qsb->iov[index];
> +
> +        s = iov->iov_base;
> +
> +        to_copy = iov->iov_len - s_off;
> +        if (to_copy > all_copy) {
> +            to_copy = all_copy;
> +        }
> +        memcpy(&buffer[d_off], &s[s_off], to_copy);
> +
> +        d_off += to_copy;
> +        all_copy -= to_copy;
> +
> +        s_off = 0;
> +        index++;
> +    }
> +
> +    return count;
> +}
> +
> +/**
> + * Grow the QEMUSizedBuffer to the given size and allocate
> + * memory for it.
> + *
> + * @qsb: A QEMUSizedBuffer
> + * @new_size: The new size of the buffer
> + *
> + * Return:
> + *    a negative error code in case of memory allocation failure
> + * or
> + *    the new size of the buffer. The returned size may be greater or equal
> + *    to @new_size.
> + */
> +static ssize_t qsb_grow(QEMUSizedBuffer *qsb, size_t new_size)
> +{
> +    size_t needed_chunks, i;
> +
> +    if (qsb->size < new_size) {
> +        struct iovec *new_iov;
> +        size_t size_diff = new_size - qsb->size;
> +        size_t chunk_size = (size_diff > QSB_MAX_CHUNK_SIZE)
> +                             ? QSB_MAX_CHUNK_SIZE : QSB_CHUNK_SIZE;
> +
> +        needed_chunks = DIV_ROUND_UP(size_diff, chunk_size);
> +
> +        new_iov = g_try_malloc_n(qsb->n_iov + needed_chunks,
> +                                 sizeof(struct iovec));
> +        if (new_iov == NULL) {
> +            return -ENOMEM;
> +        }
> +
> +        /* Allocate new chunks as needed into new_iov */
> +        for (i = qsb->n_iov; i < qsb->n_iov + needed_chunks; i++) {
> +            new_iov[i].iov_base = g_try_malloc0(chunk_size);
> +            new_iov[i].iov_len = chunk_size;
> +            if (!new_iov[i].iov_base) {
> +                size_t j;
> +
> +                /* Free previously allocated new chunks */
> +                for (j = qsb->n_iov; j < i; j++) {
> +                    g_free(new_iov[j].iov_base);
> +                }
> +                g_free(new_iov);
> +
> +                return -ENOMEM;
> +            }
> +        }
> +
> +        /*
> +         * Now we can't get any allocation errors, copy over to new iov
> +         * and switch.
> +         */
> +        for (i = 0; i < qsb->n_iov; i++) {
> +            new_iov[i] = qsb->iov[i];
> +        }
> +
> +        qsb->n_iov += needed_chunks;
> +        g_free(qsb->iov);
> +        qsb->iov = new_iov;
> +        qsb->size += (needed_chunks * chunk_size);
> +    }
> +
> +    return qsb->size;
> +}
> +
> +/**
> + * Write into the QEMUSizedBuffer at a given position and a given
> + * number of bytes. This function will automatically grow the
> + * QEMUSizedBuffer.
> + *
> + * @qsb: A QEMUSizedBuffer
> + * @source: A byte array to copy data from
> + * @pos: The position within the @qsb to write data to
> + * @size: The number of bytes to copy into the @qsb
> + *
> + * Returns @size or a negative error code in case of memory allocation failure,
> + *           or with an invalid 'pos'
> + */
> +ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *source,
> +                     off_t pos, size_t count)
> +{
> +    ssize_t rc = qsb_grow(qsb, pos + count);
> +    size_t to_copy;
> +    size_t all_copy = count;
> +    const struct iovec *iov;
> +    ssize_t index;
> +    char *dest;
> +    off_t d_off, s_off = 0;
> +
> +    if (rc < 0) {
> +        return rc;
> +    }
> +
> +    if (pos + count > qsb->used) {
> +        qsb->used = pos + count;
> +    }
> +
> +    index = qsb_get_iovec(qsb, pos, &d_off);
> +    if (index < 0) {
> +        return -EINVAL;
> +    }
> +
> +    while (all_copy > 0) {
> +        iov = &qsb->iov[index];
> +
> +        dest = iov->iov_base;
> +
> +        to_copy = iov->iov_len - d_off;
> +        if (to_copy > all_copy) {
> +            to_copy = all_copy;
> +        }
> +
> +        memcpy(&dest[d_off], &source[s_off], to_copy);
> +
> +        s_off += to_copy;
> +        all_copy -= to_copy;
> +
> +        d_off = 0;
> +        index++;
> +    }
> +
> +    return count;
> +}
> +
> +/**
> + * Create a deep copy of the given QEMUSizedBuffer.
> + *
> + * @qsb: A QEMUSizedBuffer
> + *
> + * Returns a clone of @qsb or NULL on allocation failure
> + */
> +QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *qsb)
> +{
> +    QEMUSizedBuffer *out = qsb_create(NULL, qsb_get_length(qsb));
> +    size_t i;
> +    ssize_t res;
> +    off_t pos = 0;
> +
> +    if (!out) {
> +        return NULL;
> +    }
> +
> +    for (i = 0; i < qsb->n_iov; i++) {
> +        res =  qsb_write_at(out, qsb->iov[i].iov_base,
> +                            pos, qsb->iov[i].iov_len);
> +        if (res < 0) {
> +            qsb_free(out);
> +            return NULL;
> +        }
> +        pos += res;
> +    }
> +
> +    return out;
> +}
> +
> +typedef struct QEMUBuffer {
> +    QEMUSizedBuffer *qsb;
> +    QEMUFile *file;
> +} QEMUBuffer;
> +
> +static int buf_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
> +{
> +    QEMUBuffer *s = opaque;
> +    ssize_t len = qsb_get_length(s->qsb) - pos;
> +
> +    if (len <= 0) {
> +        return 0;
> +    }
> +
> +    if (len > size) {
> +        len = size;
> +    }
> +    return qsb_get_buffer(s->qsb, pos, len, buf);
> +}
> +
> +static int buf_put_buffer(void *opaque, const uint8_t *buf,
> +                          int64_t pos, int size)
> +{
> +    QEMUBuffer *s = opaque;
> +
> +    return qsb_write_at(s->qsb, buf, pos, size);
> +}
> +
> +static int buf_close(void *opaque)
> +{
> +    QEMUBuffer *s = opaque;
> +
> +    qsb_free(s->qsb);
> +
> +    g_free(s);
> +
> +    return 0;
> +}
> +
> +const QEMUSizedBuffer *qemu_buf_get(QEMUFile *f)
> +{
> +    QEMUBuffer *p;
> +
> +    qemu_fflush(f);
> +
> +    p = f->opaque;
> +
> +    return p->qsb;
> +}
> +
> +static const QEMUFileOps buf_read_ops = {
> +    .get_buffer = buf_get_buffer,
> +    .close =      buf_close,
> +};
> +
> +static const QEMUFileOps buf_write_ops = {
> +    .put_buffer = buf_put_buffer,
> +    .close =      buf_close,
> +};
> +
> +QEMUFile *qemu_bufopen(const char *mode, QEMUSizedBuffer *input)
> +{
> +    QEMUBuffer *s;
> +
> +    if (mode == NULL || (mode[0] != 'r' && mode[0] != 'w') ||
> +        mode[1] != '\0') {
> +        error_report("qemu_bufopen: Argument validity check failed");
> +        return NULL;
> +    }
> +
> +    s = g_malloc0(sizeof(QEMUBuffer));
> +    if (mode[0] == 'r') {
> +        s->qsb = input;
> +    }
> +
> +    if (s->qsb == NULL) {
> +        s->qsb = qsb_create(NULL, 0);
> +    }
> +    if (!s->qsb) {
> +        g_free(s);
> +        error_report("qemu_bufopen: qsb_create failed");
> +        return NULL;
> +    }
> +
> +
> +    if (mode[0] == 'r') {
> +        s->file = qemu_fopen_ops(s, &buf_read_ops);
> +    } else {
> +        s->file = qemu_fopen_ops(s, &buf_write_ops);
> +    }
> +    return s->file;
> +}
>