[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Patch v3 2/2] tools/libxc: Implement writev_exact() in the same style as write_exact()
At 07/16/2014 10:32 PM, Andrew Cooper Wrote: > This implementation of writev_exact() will cope with an iovcnt greater than > IOV_MAX because glibc will actually let this work anyway, and it is very > useful not to have to work about this in the caller of writev_exact(). The > caller is still required to ensure that the sum of iov_len's doesn't overflow > a ssize_t. > > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> > CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx> > CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> > > --- > v3: > * Re-add adjustment for partial writes. > * Split min/max adjustment into separate patch. > > v2: > * Remove adjustment for partial writes of a specific iov[] entry. > --- > tools/libxc/xc_private.c | 60 > ++++++++++++++++++++++++++++++++++++++++++++++ > tools/libxc/xc_private.h | 2 ++ > 2 files changed, 62 insertions(+) > > diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c > index 1c214dd..0941b06 100644 > --- a/tools/libxc/xc_private.c > +++ b/tools/libxc/xc_private.c > @@ -858,6 +858,66 @@ int write_exact(int fd, const void *data, size_t size) > return 0; > } > > +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. */ > + while ( iov[iov_idx].iov_len == 0 ) > + if ( ++iov_idx == iovcnt ) > + goto out; set saved_errn to 0 before goto out? > + > + len = writev(fd, &iov[iov_idx], min(iovcnt - iov_idx, IOV_MAX)); > + saved_errno = errno; > + > + if ( (len == -1) && (errno == EINTR) ) > + continue; > + if ( len <= 0 ) > + { > + rc = -1; > + goto out; > + } > + > + /* Check iov[] to see whether we had a partial or complete write. */ > + while ( len > 0 && (iov_idx < iovcnt) ) > + { > + if ( len >= iov[iov_idx].iov_len ) > + len -= iov[iov_idx++].iov_len; > + else > + { > + /* Partial write of iov[iov_idx]. Copy iov so we can adjust > + * element iov_idx and resubmit the rest. */ > + if ( !local_iov ) > + { > + local_iov = malloc(iovcnt * sizeof(*iov)); > + if ( !local_iov ) > + { > + saved_errno = ENOMEM; > + goto out; > + } > + > + iov = memcpy(local_iov, iov, iovcnt * sizeof(*iov)); > + } > + > + local_iov[iov_idx].iov_base += len; > + local_iov[iov_idx].iov_len -= len; > + break; > + } > + } > + } > + > + saved_errno = 0; > + > + out: > + free(local_iov); > + errno = saved_errno; > + return rc; > +} > + > int xc_ffs8(uint8_t x) > { > int i; > diff --git a/tools/libxc/xc_private.h b/tools/libxc/xc_private.h > index ce7e81e..1f06166 100644 > --- a/tools/libxc/xc_private.h > +++ b/tools/libxc/xc_private.h > @@ -28,6 +28,7 @@ > #include <sys/stat.h> > #include <stdlib.h> > #include <sys/ioctl.h> > +#include <sys/uio.h> > > #include "xenctrl.h" > #include "xenctrlosdep.h" > @@ -343,6 +344,7 @@ 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 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); > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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