fa778fffdf
Upstream NBD protocol recently added the ability to efficiently write zeroes without having to send the zeroes over the wire, along with a flag to control whether the client wants a hole. The generic block code takes care of falling back to the obvious write of lots of zeroes if we return -ENOTSUP because the server does not have WRITE_ZEROES. Ideally, since NBD_CMD_WRITE_ZEROES does not involve any data over the wire, we want to support transactions that are much larger than the normal 32M limit imposed on NBD_CMD_WRITE. But the server may still have a limit smaller than UINT_MAX, so until experimental NBD protocol additions for advertising various command sizes is finalized (see [1], [2]), for now we just stick to the same limits as normal writes. [1] https://github.com/yoe/nbd/blob/extension-info/doc/proto.md [2] https://sourceforge.net/p/nbd/mailman/message/35081223/ Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1476469998-28592-17-git-send-email-eblake@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
61 lines
1.9 KiB
C
61 lines
1.9 KiB
C
#ifndef NBD_CLIENT_H
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#define NBD_CLIENT_H
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#include "qemu-common.h"
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#include "block/nbd.h"
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#include "block/block_int.h"
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#include "io/channel-socket.h"
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/* #define DEBUG_NBD */
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#if defined(DEBUG_NBD)
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#define logout(fmt, ...) \
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fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__)
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#else
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#define logout(fmt, ...) ((void)0)
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#endif
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#define MAX_NBD_REQUESTS 16
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typedef struct NBDClientSession {
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QIOChannelSocket *sioc; /* The master data channel */
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QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
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uint16_t nbdflags;
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off_t size;
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CoMutex send_mutex;
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CoQueue free_sema;
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Coroutine *send_coroutine;
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int in_flight;
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Coroutine *recv_coroutine[MAX_NBD_REQUESTS];
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NBDReply reply;
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bool is_unix;
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} NBDClientSession;
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NBDClientSession *nbd_get_client_session(BlockDriverState *bs);
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int nbd_client_init(BlockDriverState *bs,
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QIOChannelSocket *sock,
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const char *export_name,
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QCryptoTLSCreds *tlscreds,
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const char *hostname,
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Error **errp);
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void nbd_client_close(BlockDriverState *bs);
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int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int count);
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int nbd_client_co_flush(BlockDriverState *bs);
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int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
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uint64_t bytes, QEMUIOVector *qiov, int flags);
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int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
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int count, BdrvRequestFlags flags);
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int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
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uint64_t bytes, QEMUIOVector *qiov, int flags);
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void nbd_client_detach_aio_context(BlockDriverState *bs);
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void nbd_client_attach_aio_context(BlockDriverState *bs,
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AioContext *new_context);
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#endif /* NBD_CLIENT_H */
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