[Virtio-fs] [PATCH v7 2/7] fuse: make DAX mount option a tri-state
JeffleXu
jefflexu at linux.alibaba.com
Fri Nov 12 01:52:14 UTC 2021
On 11/12/21 2:52 AM, Vivek Goyal wrote:
> On Tue, Nov 02, 2021 at 01:25:59PM +0800, Jeffle Xu wrote:
>> We add 'always', 'never', and 'inode' (default). '-o dax' continues to
>> operate the same which is equivalent to 'always'.
>>
>> The following behavior is consistent with that on ext4/xfs:
>> - The default behavior (when neither '-o dax' nor
>> '-o dax=always|never|inode' option is specified) is equal to 'inode'
>> mode, while 'dax=inode' won't be printed among the mount option list.
>> - The 'inode' mode is only advisory. It will silently fallback to
>> 'never' mode if fuse server doesn't support that.
>>
>> Also noted that by the time of this commit, 'inode' mode is actually
>> equal to 'always' mode, before the per inode DAX flag is introduced in
>> the following patch.
>>
>> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
>> ---
>> fs/fuse/dax.c | 9 ++++++++-
>> fs/fuse/fuse_i.h | 20 ++++++++++++++++++--
>> fs/fuse/inode.c | 10 +++++++---
>> fs/fuse/virtio_fs.c | 18 +++++++++++++++---
>> 4 files changed, 48 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
>> index 8c187b04874e..91c8d146dbc4 100644
>> --- a/fs/fuse/dax.c
>> +++ b/fs/fuse/dax.c
>> @@ -1284,11 +1284,14 @@ static int fuse_dax_mem_range_init(struct fuse_conn_dax *fcd)
>> return ret;
>> }
>>
>> -int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev)
>> +int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode dax_mode,
>> + struct dax_device *dax_dev)
>> {
>> struct fuse_conn_dax *fcd;
>> int err;
>>
>> + fc->dax_mode = dax_mode;
>> +
>> if (!dax_dev)
>> return 0;
>>
>> @@ -1335,6 +1338,10 @@ static const struct address_space_operations fuse_dax_file_aops = {
>> static bool fuse_should_enable_dax(struct inode *inode)
>> {
>> struct fuse_conn *fc = get_fuse_conn(inode);
>> + enum fuse_dax_mode dax_mode = fc->dax_mode;
>> +
>> + if (dax_mode == FUSE_DAX_NEVER)
>> + return false;
>>
>> if (!fc->dax)
>> return false;
>> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
>> index f55f9f94b1a4..4f9c2358f343 100644
>> --- a/fs/fuse/fuse_i.h
>> +++ b/fs/fuse/fuse_i.h
>> @@ -480,6 +480,18 @@ struct fuse_dev {
>> struct list_head entry;
>> };
>>
>> +enum fuse_dax_mode {
>> + FUSE_DAX_NONE, /* default */
>> + FUSE_DAX_ALWAYS, /* "-o dax=always" */
>> + FUSE_DAX_NEVER, /* "-o dax=never" */
>> + FUSE_DAX_INODE, /* "-o dax=inode" */
>> +};
> Hi,
>
> Not sure why do we need FUSE_DAX_NONE. Now default is FUSE_DAX_INODE
> and "-o dax" will map to FUSE_DAX_ALWAYS. So after this patch series,
> nobody should be using FUSE_DAX_NONE state at all? So we should be
> able to get rid of entirely?
>
>> +
>> +static inline bool fuse_is_inode_dax_mode(enum fuse_dax_mode mode)
>> +{
>> + return mode == FUSE_DAX_INODE || mode == FUSE_DAX_NONE;
>> +}
>
> This is confusing. Why FUSE_DAX_NONE is equivalent to inode dax mode.
> Is it because you want FUSE_DAX_INODE as default. If that's the case,
> lets get rid of FUSE_DAX_NONE and just set FUSE_DAX_INODE as default?
>
>> +
>> struct fuse_fs_context {
>> int fd;
>> struct file *file;
>> @@ -497,7 +509,7 @@ struct fuse_fs_context {
>> bool no_control:1;
>> bool no_force_umount:1;
>> bool legacy_opts_show:1;
>> - bool dax:1;
>> + enum fuse_dax_mode dax_mode;
>> unsigned int max_read;
>> unsigned int blksize;
>> const char *subtype;
>> @@ -802,6 +814,9 @@ struct fuse_conn {
>> struct list_head devices;
>>
>> #ifdef CONFIG_FUSE_DAX
>> + /* Dax mode */
>> + enum fuse_dax_mode dax_mode;
>> +
>> /* Dax specific conn data, non-NULL if DAX is enabled */
>> struct fuse_conn_dax *dax;
>> #endif
>> @@ -1258,7 +1273,8 @@ ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
>> ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
>> int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma);
>> int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start, u64 dmap_end);
>> -int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev);
>> +int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode mode,
>> + struct dax_device *dax_dev);
>> void fuse_dax_conn_free(struct fuse_conn *fc);
>> bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi);
>> void fuse_dax_inode_init(struct inode *inode);
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index 12d49a1914e8..15ce56f9cf11 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -734,8 +734,12 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
>> seq_printf(m, ",blksize=%lu", sb->s_blocksize);
>> }
>> #ifdef CONFIG_FUSE_DAX
>> - if (fc->dax)
>> - seq_puts(m, ",dax");
>> + if (fc->dax_mode == FUSE_DAX_ALWAYS)
>> + seq_puts(m, ",dax=always");
>> + else if (fc->dax_mode == FUSE_DAX_NEVER)
>> + seq_puts(m, ",dax=never");
>> + else if (fc->dax_mode == FUSE_DAX_INODE)
>> + seq_puts(m, ",dax=inode");
>
> I guess this answers the question about FUSE_DAX_NONE. You want to
> keep track if user passed in "dax=inode" or you defaulted to dax=inode.
> And if you defaulted to "dax=inode" you don't want to show it in fuse
> options.
Yes, so that this behavior of printing fuse options is consistnet with
ext4/xfs.
>
> Hmm..., if that's the intent, I would rather keep the names like this.
>
> FUSE_DAX_INODE_USER and FUSE_DAX_INODE_DEFAULT. This clearly tells
> me the difference between two states.
OK this naming is obviously more readable.
>
>> #endif
>>
>> return 0;
>> @@ -1481,7 +1485,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
>> sb->s_subtype = ctx->subtype;
>> ctx->subtype = NULL;
>> if (IS_ENABLED(CONFIG_FUSE_DAX)) {
>> - err = fuse_dax_conn_alloc(fc, ctx->dax_dev);
>> + err = fuse_dax_conn_alloc(fc, ctx->dax_mode, ctx->dax_dev);
>> if (err)
>> goto err;
>> }
>> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
>> index 94fc874f5de7..e8c404946c63 100644
>> --- a/fs/fuse/virtio_fs.c
>> +++ b/fs/fuse/virtio_fs.c
>> @@ -88,12 +88,21 @@ struct virtio_fs_req_work {
>> static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
>> struct fuse_req *req, bool in_flight);
>>
>> +static const struct constant_table dax_param_enums[] = {
>> + {"always", FUSE_DAX_ALWAYS },
>> + {"never", FUSE_DAX_NEVER },
>> + {"inode", FUSE_DAX_INODE },
>> + {}
>> +};
>> +
>> enum {
>> OPT_DAX,
>> + OPT_DAX_ENUM,
>> };
>>
>> static const struct fs_parameter_spec virtio_fs_parameters[] = {
>> fsparam_flag("dax", OPT_DAX),
>> + fsparam_enum("dax", OPT_DAX_ENUM, dax_param_enums),
>> {}
>> };
>>
>> @@ -110,7 +119,10 @@ static int virtio_fs_parse_param(struct fs_context *fsc,
>>
>> switch (opt) {
>> case OPT_DAX:
>> - ctx->dax = 1;
>> + ctx->dax_mode = FUSE_DAX_ALWAYS;
>> + break;
>> + case OPT_DAX_ENUM:
>> + ctx->dax_mode = result.uint_32;
>> break;
>> default:
>> return -EINVAL;
>> @@ -1326,8 +1338,8 @@ static int virtio_fs_fill_super(struct super_block *sb, struct fs_context *fsc)
>>
>> /* virtiofs allocates and installs its own fuse devices */
>> ctx->fudptr = NULL;
>> - if (ctx->dax) {
>> - if (!fs->dax_dev) {
>> + if (ctx->dax_mode != FUSE_DAX_NEVER) {
> ^^
> Why do we need this check. IOW, why following check alone is not
> sufficient.
>
>> + if (ctx->dax_mode == FUSE_DAX_ALWAYS && !fs->dax_dev) {
> ^^^
>
> If user specified dax mode FUSE_DAX_ALWAYS, we need to make sure fs device
> supports dax. And second if condition seems sufficient.
>
The complete code snippet is like:
```
if (ctx->dax_mode != FUSE_DAX_NEVER) {
if (ctx->dax_mode == FUSE_DAX_ALWAYS && !fs->dax_dev) {
err = -EINVAL;
pr_err("virtio-fs: dax can't be enabled as
filesystem"
" device does not support it.\n");
goto err_free_fuse_devs;
}
ctx->dax_dev = fs->dax_dev;
}
```
So we need the first if condition statement, so that 'ctx->dax_dev' is
assigned in both FUSE_DAX_ALWAYS and FUSE_DAX_INODE cases.
--
Thanks,
Jeffle
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