|
From: | Denis V. Lunev |
Subject: | Re: [Qemu-devel] [PATCH for-2.7 v2 05/17] raw-posix: Implement .bdrv_lockf |
Date: | Mon, 18 Apr 2016 08:30:28 +0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 |
On 04/18/2016 04:12 AM, Fam Zheng wrote:
On Sat, 04/16 16:29, Denis V. Lunev wrote:On 04/15/2016 06:27 AM, Fam Zheng wrote:virtlockd in libvirt locks the first byte, we lock byte 1 to avoid the intervene. Suggested-by: "Daniel P. Berrange" <address@hidden> Signed-off-by: Fam Zheng <address@hidden> --- block/raw-posix.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/block/raw-posix.c b/block/raw-posix.c index 906d5c9..3a2c17f 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -35,6 +35,7 @@ #include "raw-aio.h" #include "qapi/util.h" #include "qapi/qmp/qstring.h" +#include "glib.h" #if defined(__APPLE__) && (__MACH__) #include <paths.h> @@ -397,6 +398,38 @@ static void raw_attach_aio_context(BlockDriverState *bs, #endif } +static int raw_lockf(BlockDriverState *bs, BdrvLockfCmd cmd) +{ + + BDRVRawState *s = bs->opaque; + int ret; + struct flock fl = (struct flock) { + .l_whence = SEEK_SET, + /* Locking byte 1 avoids interfereing with virtlockd. */ + .l_start = 1, + .l_len = 1, + }; + + switch (cmd) { + case BDRV_LOCKF_RWLOCK: + fl.l_type = F_WRLCK; + break; + case BDRV_LOCKF_ROLOCK: + fl.l_type = F_RDLCK; + break; + case BDRV_LOCKF_UNLOCK: + fl.l_type = F_UNLCK; + break; + default: + abort(); + } + ret = fcntl(s->fd, F_SETLK, &fl); + if (ret) { + ret = -errno; + } + return ret; +} + #ifdef CONFIG_LINUX_AIO static int raw_set_aio(void **aio_ctx, int *use_aio, int bdrv_flags) { @@ -1960,6 +1993,8 @@ BlockDriver bdrv_file = { .bdrv_detach_aio_context = raw_detach_aio_context, .bdrv_attach_aio_context = raw_attach_aio_context, + .bdrv_lockf = raw_lockf, + .create_opts = &raw_create_opts, };would it be better to use int flock(int fd, int operation); DESCRIPTION Apply or remove an advisory lock on the open file specified by fd. The argument operation is one of the following: LOCK_SH Place a shared lock. More than one process may hold a shared lock for a given file at a given time. LOCK_EX Place an exclusive lock. Only one process may hold an exclusive lock for a given file at a given time. LOCK_UN Remove an existing lock held by this process. for this purpose? Sorry that missed this point in the initial review... We will not intersect with libvirt for the case.As noted in the cover letter, flock() is nop on NFS mount points on Linux, so fcntl is safer. Fam
that seems STRANGE to me. For the time being flock() was working for Linux NFS server. Here is the implementation. int nfs_flock(struct file *filp, int cmd, struct file_lock *fl) { struct inode *inode = filp->f_mapping->host; int is_local = 0; dprintk("NFS: flock(%pD2, t=%x, fl=%x)\n", filp, fl->fl_type, fl->fl_flags); if (!(fl->fl_flags & FL_FLOCK)) return -ENOLCK; /** The NFSv4 protocol doesn't support LOCK_MAND, which is not part of
* any standard. In principle we might be able to support LOCK_MAND* on NFSv2/3 since NLMv3/4 support DOS share modes, but for now the
* NFS code is not set up for it. */ if (fl->fl_type & LOCK_MAND) return -EINVAL; if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK) is_local = 1;/* We're simulating flock() locks using posix locks on the server */
if (fl->fl_type == F_UNLCK) return do_unlk(filp, cmd, fl, is_local); return do_setlk(filp, cmd, fl, is_local); } Den
[Prev in Thread] | Current Thread | [Next in Thread] |