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xen.sr-readv_exact.patch
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File xen.sr-readv_exact.patch of Package xen
From: Olaf Hering <olaf@aepfle.de> Date: Wed, 28 Oct 2020 12:07:36 +0100 Subject: sr readv_exact tools: add readv_exact to libxenctrl Read a batch of iovec's. Short reads are the common case, finish the trailing iov with read_exact. Signed-off-by: Olaf Hering <olaf@aepfle.de> v2: - add comment to short-read handling --- tools/libs/ctrl/xc_private.c | 57 ++++++++- tools/libs/ctrl/xc_private.h | 1 + 2 files changed, 57 insertions(+), 1 deletion(-) --- a/tools/libs/ctrl/xc_private.c +++ b/tools/libs/ctrl/xc_private.c @@ -690,40 +690,95 @@ int write_exact(int fd, const void *data, size_t size) if ( (len == -1) && (errno == EINTR) ) continue; if ( len <= 0 ) return -1; offset += len; } return 0; } #if defined(__MINIOS__) /* - * MiniOS's libc doesn't know about writev(). Implement it as multiple write()s. + * MiniOS's libc doesn't know about readv/writev(). + * Implement it as multiple read/write()s. */ +int readv_exact(int fd, const struct iovec *iov, int iovcnt) +{ + int rc, i; + + for ( i = 0; i < iovcnt; ++i ) + { + rc = read_exact(fd, iov[i].iov_base, iov[i].iov_len); + if ( rc ) + return rc; + } + + return 0; +} + int writev_exact(int fd, const struct iovec *iov, int iovcnt) { int rc, i; for ( i = 0; i < iovcnt; ++i ) { rc = write_exact(fd, iov[i].iov_base, iov[i].iov_len); if ( rc ) return rc; } return 0; } #else +int readv_exact(int fd, const struct iovec *iov, int iovcnt) +{ + int rc = 0, idx = 0; + ssize_t len; + + while ( idx < iovcnt ) + { + len = readv(fd, &iov[idx], min(iovcnt - idx, IOV_MAX)); + if ( len == -1 && errno == EINTR ) + continue; + if ( len <= 0 ) + { + rc = -1; + goto out; + } + + /* Finish a potential short read in the last iov */ + while ( len > 0 && idx < iovcnt ) + { + if ( len >= iov[idx].iov_len ) + { + len -= iov[idx].iov_len; + } + else + { + void *p = iov[idx].iov_base + len; + size_t l = iov[idx].iov_len - len; + + rc = read_exact(fd, p, l); + if ( rc ) + goto out; + len = 0; + } + idx++; + } + } +out: + return rc; +} + int writev_exact(int fd, const struct iovec *iov, int iovcnt) { struct iovec *local_iov = NULL; int rc = 0, iov_idx = 0, saved_errno = 0; ssize_t len; while ( iov_idx < iovcnt ) { /* * Skip over iov[] entries with 0 length. * * This is needed to cover the case where we took a partial write and --- a/tools/libs/ctrl/xc_private.h +++ b/tools/libs/ctrl/xc_private.h @@ -386,24 +386,25 @@ struct xc_mmu { mmu_update_t updates[MAX_MMU_UPDATES]; int idx; unsigned int subject; }; /* Structure returned by xc_alloc_mmu_updates must be free()'ed by caller. */ struct xc_mmu *xc_alloc_mmu_updates(xc_interface *xch, unsigned int subject); int xc_add_mmu_update(xc_interface *xch, struct xc_mmu *mmu, unsigned long long ptr, unsigned long long val); int xc_flush_mmu_updates(xc_interface *xch, struct xc_mmu *mmu); /* Return 0 on success; -1 on error setting errno. */ int read_exact(int fd, void *data, size_t size); /* EOF => -1, errno=0 */ +int readv_exact(int fd, const struct iovec *iov, int iovcnt); int write_exact(int fd, const void *data, size_t size); int writev_exact(int fd, const struct iovec *iov, int iovcnt); int xc_ffs8(uint8_t x); int xc_ffs16(uint16_t x); int xc_ffs32(uint32_t x); int xc_ffs64(uint64_t x); #define DOMPRINTF(fmt, args...) xc_dom_printf(dom->xch, fmt, ## args) #define DOMPRINTF_CALLED(xch) xc_dom_printf((xch), "%s: called", __FUNCTION__) /**
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