On 12/10/21 6:02 AM, Vivek Goyal wrote:
> On Tue, Nov 02, 2021 at 01:56:45PM +0800, Jeffle Xu wrote:
>> The per inode DAX feature in ext4/xfs uses the persistent inode flag,
>> i.e. FS_DAX_FL/FS_XFLAG_DAX, to indicate if DAX shall be enabled for
>> this file or not when filesystem is mounted in per inode DAX mode.
>>
>> To keep compatible with this feature in ext4/xfs, virtiofs also supports
>> enabling DAX depending on the persistent inode flag, which may be
>> set/cleared by users inside guest or admin on host.
>>
>> This policy is used when '-o dax=inode' option is specified for
>> virtiofsd.
>>
>> Signed-off-by: Jeffle Xu <jeffl...@linux.alibaba.com>
>> ---
>> tools/virtiofsd/passthrough_ll.c | 33 ++++++++++++++++++++++++++++++++
>> 1 file changed, 33 insertions(+)
>>
>> diff --git a/tools/virtiofsd/passthrough_ll.c
>> b/tools/virtiofsd/passthrough_ll.c
>> index 999c906da2..dac5063594 100644
>> --- a/tools/virtiofsd/passthrough_ll.c
>> +++ b/tools/virtiofsd/passthrough_ll.c
>> @@ -1026,6 +1026,35 @@ static int do_statx(struct lo_data *lo, int dirfd,
>> const char *pathname,
>> return 0;
>> }
>>
>> +static bool lo_should_enable_dax(struct lo_data *lo, struct lo_inode *inode,
>> + struct fuse_entry_param *e)
>> +{
>> + if (lo->dax == INODE_DAX_NONE || !S_ISREG(e->attr.st_mode)) {
>> + return false;
>> + }
>> +
>> + if (lo->dax == INODE_DAX_INODE) {
>> + int res, fd;
>> + int ret = false;
>> + unsigned int attr;
>> +
>> + fd = lo_inode_open(lo, inode, O_RDONLY);
>> + if (fd == -1) {
>> + return false;
>> + }
>> +
>> + res = ioctl(fd, FS_IOC_GETFLAGS, &attr);
>> + if (!res && (attr & FS_DAX_FL)) {
>> + ret = true;
>> + }
>> +
>> + close(fd);
>> + return ret;
>> + }
>> +
>> + return false;
>> +}
>> +
>> /*
>> * Increments nlookup on the inode on success. unref_inode_lolocked() must
>> be
>> * called eventually to decrement nlookup again. If inodep is non-NULL, the
>> @@ -1116,6 +1145,10 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t
>> parent, const char *name,
>> }
>> e->ino = inode->fuse_ino;
>>
>> + if (lo_should_enable_dax(lo, inode, e)) {
>> + e->attr_flags |= FUSE_ATTR_DAX;
>> + }
>> +
>
> If we were too strict then we should probably add a
> lo_should_enable_dax() call in lo_getattr() as well?
Good catch. FUSE_GETATTR could also reply the per inode DAX flag.
>
> I guess for now it is ok. Overhead of checking fs_xflag_dax seems
> enough and not many might care about immediate chnage of dax
> status in guest.
>
OK, we can easily add it if it's needed later.
--
Thanks,
Jeffle
_______________________________________________
Virtio-fs mailing list
Virtio-fs@redhat.com
https://listman.redhat.com/mailman/listinfo/virtio-fs