Messages in this thread | | | Date | Mon, 17 Dec 2012 18:13:34 +0400 | From | "Maxim V. Patlasov" <> | Subject | Re: [PATCH 5/6] fuse: truncate file if async dio failed |
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Hi,
12/15/2012 12:16 AM, Brian Foster пишет: > On 12/14/2012 10:21 AM, Maxim V. Patlasov wrote: >> The patch improves error handling in fuse_direct_IO(): if we successfully >> submitted several fuse requests on behalf of synchronous direct write >> extending file and some of them failed, let's try to do our best to clean-up. >> >> Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com> >> --- >> fs/fuse/file.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++-- >> 1 files changed, 53 insertions(+), 2 deletions(-) >> >> diff --git a/fs/fuse/file.c b/fs/fuse/file.c >> index 05eed23..b6e9b8d 100644 >> --- a/fs/fuse/file.c >> +++ b/fs/fuse/file.c >> @@ -2340,6 +2340,53 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc, >> return 0; >> } >> >> +static void fuse_do_truncate(struct file *file) >> +{ >> + struct fuse_file *ff = file->private_data; >> + struct inode *inode = file->f_mapping->host; >> + struct fuse_conn *fc = get_fuse_conn(inode); >> + struct fuse_req *req; >> + struct fuse_setattr_in inarg; >> + struct fuse_attr_out outarg; >> + int err; >> + >> + req = fuse_get_req_nopages(fc); >> + if (IS_ERR(req)) { >> + printk(KERN_WARNING "failed to allocate req for truncate " >> + "(%ld)\n", PTR_ERR(req)); >> + return; >> + } >> + >> + memset(&inarg, 0, sizeof(inarg)); >> + memset(&outarg, 0, sizeof(outarg)); >> + >> + inarg.valid |= FATTR_SIZE; >> + inarg.size = i_size_read(inode); >> + >> + inarg.valid |= FATTR_FH; >> + inarg.fh = ff->fh; >> + >> + req->in.h.opcode = FUSE_SETATTR; >> + req->in.h.nodeid = get_node_id(inode); >> + req->in.numargs = 1; >> + req->in.args[0].size = sizeof(inarg); >> + req->in.args[0].value = &inarg; >> + req->out.numargs = 1; >> + if (fc->minor < 9) >> + req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE; >> + else >> + req->out.args[0].size = sizeof(outarg); >> + req->out.args[0].value = &outarg; >> + >> + fuse_request_send(fc, req); >> + err = req->out.h.error; >> + fuse_put_request(fc, req); >> + >> + if (err) >> + printk(KERN_WARNING "failed to truncate to %lld with error " >> + "%d\n", i_size_read(inode), err); >> +} >> + > fuse_do_truncate() looks fairly close to fuse_do_setattr(). Is there any > reason we couldn't make fuse_do_setattr() non-static, change the dentry > parameter to an inode and use that?
fuse_do_setattr() performs extra checks that fuse_do_truncate() needn't. Some of them are harmless, some not: fuse_allow_task() may return 0 if task credentials changed. E.g. super-user successfully opened a file, then setuid(other_user_uid), then write(2) to the file. write(2) doesn't check uid, but fuse_do_truncate() - via fuse_allow_task() - does.
This non-POSIX behaviour (ftruncate(2) returning -1 with errno==EACCES) was introduced long time ago:
> commit e57ac68378a287d6336d187b26971f35f7ee7251 > Author: Miklos Szeredi <mszeredi@suse.cz> > Date: Thu Oct 18 03:06:58 2007 -0700 > > fuse: fix allowing operations > > The following operation didn't check if sending the request was > allowed: > > setattr > listxattr > statfs > > Some other operations don't explicitly do the check, but VFS calls > ->permission() which checks this. > > Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
and I'm not sure whether it was done intentionally or not. Maybe Miklos could shed some light on it...
Thanks, Maxim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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