From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hongyang Yang Subject: Re: [PATCH v2] tools/libxc: Implement writev_exact() in the same style as write_exact() Date: Tue, 8 Jul 2014 11:30:49 +0800 Message-ID: <53BB65E9.4010805@cn.fujitsu.com> References: <1404728318-13474-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1404728318-13474-1-git-send-email-andrew.cooper3@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper , Xen-devel Cc: Ian Jackson , Ian Campbell List-Id: xen-devel@lists.xenproject.org On 07/07/2014 06:18 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. > > Promote the MAX() and MIN() macro definitions from xg_save_restore.h to > xc_private.h > > Signed-off-by: Andrew Cooper > CC: Ian Campbell > CC: Ian Jackson Reviewed-by: Yang Hongyang > > --- > > v2: Remove adjustment for partial writes of a specific iov[] entry. > --- > tools/libxc/xc_private.c | 31 +++++++++++++++++++++++++++++++ > tools/libxc/xc_private.h | 9 +++++++++ > tools/libxc/xg_save_restore.h | 6 ------ > 3 files changed, 40 insertions(+), 6 deletions(-) > > diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c > index a3da614..d610984 100644 > --- a/tools/libxc/xc_private.c > +++ b/tools/libxc/xc_private.c > @@ -854,6 +854,37 @@ int write_exact(int fd, const void *data, size_t size) > return 0; > } > > +int writev_exact(int fd, const struct iovec *iov, int iovcnt) > +{ > + int iov_idx = 0; > + ssize_t len; > + > + while ( iov_idx < iovcnt ) > + { > + /* Skip over iov[] enties with 0 length. */ > + while ( iov[iov_idx].iov_len == 0 ) > + if ( ++iov_idx == iovcnt ) > + return 0; > + > + len = writev(fd, &iov[iov_idx], MIN(iovcnt - iov_idx, IOV_MAX)); > + > + if ( (len == -1) && (errno == EINTR) ) > + continue; > + if ( len <= 0 ) > + return -1; > + > + /* Check iov[] to see whether we had a partial or complete write. */ > + while ( len > 0 && (iov_idx < iovcnt) ) > + len -= iov[iov_idx++].iov_len; > + > + /* writev() guarentees atomicity of individual iov[] elements. Sanity > + * check that the returned len did lie on an iov[] element boundary. */ > + assert(len == 0); > + } > + > + return 0; > +} > + > int xc_ffs8(uint8_t x) > { > int i; > diff --git a/tools/libxc/xc_private.h b/tools/libxc/xc_private.h > index 6cc0f2b..198b8a0 100644 > --- a/tools/libxc/xc_private.h > +++ b/tools/libxc/xc_private.h > @@ -28,6 +28,7 @@ > #include > #include > #include > +#include > > #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); > @@ -367,4 +369,11 @@ int xc_mem_event_memop(xc_interface *xch, domid_t domain_id, > void *xc_mem_event_enable(xc_interface *xch, domid_t domain_id, int param, > uint32_t *port); > > +#ifndef MAX > +#define MAX(_a, _b) ((_a) >= (_b) ? (_a) : (_b)) > +#endif > +#ifndef MIN > +#define MIN(_a, _b) ((_a) <= (_b) ? (_a) : (_b)) > +#endif > + > #endif /* __XC_PRIVATE_H__ */ > diff --git a/tools/libxc/xg_save_restore.h b/tools/libxc/xg_save_restore.h > index aa93c13..34019fa 100644 > --- a/tools/libxc/xg_save_restore.h > +++ b/tools/libxc/xg_save_restore.h > @@ -393,9 +393,3 @@ static inline int get_platform_info(xc_interface *xch, uint32_t dom, > memset(&(_p)->x32._f[0], (_v), sizeof((_p)->x32._f)); \ > } while (0) > > -#ifndef MAX > -#define MAX(_a, _b) ((_a) >= (_b) ? (_a) : (_b)) > -#endif > -#ifndef MIN > -#define MIN(_a, _b) ((_a) <= (_b) ? (_a) : (_b)) > -#endif > -- Thanks, Yang.