Re: [PATCH v2 09/18] btrfs: add parse_param callback for the new mount api

Josef Bacik
2023-11-22T16:12:13Z

On Tue, Nov 14, 2023 at 07:13:38PM +0100, David Sterba wrote:
> On Wed, Nov 08, 2023 at 02:08:44PM -0500, Josef Bacik wrote:
> > The parse_param callback handles one parameter at a time, take our
> > existing mount option parsing loop and adjust it to handle one parameter
> > at a time, and tie it into the fs_context_operations.
> >
> > Create a btrfs_fs_context object that will store the various mount
> > properties, we'll house this in fc->fs_private. This is necessary to
> > separate because remounting will use ->reconfigure, and we'll get a new
> > copy of the parsed parameters, so we can no longer directly mess with
> > the fs_info in this stage.
> >
> > In the future we'll add this to the btrfs_fs_info and update the users
> > to use the new context object instead.
> >
> > Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> > ---
> > fs/btrfs/super.c | 390 +++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 390 insertions(+)
> >
> > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> > index 0e9cb9ed6508..2f7ee78edd11 100644
> > --- a/fs/btrfs/super.c
> > +++ b/fs/btrfs/super.c
> > @@ -84,6 +84,19 @@ static void btrfs_put_super(struct super_block *sb)
> > close_ctree(btrfs_sb(sb));
> > }
> >
> > +/* Store the mount options related information. */
> > +struct btrfs_fs_context {
> > + char *subvol_name;
> > + u64 subvol_objectid;
> > + u64 max_inline;
> > + u32 commit_interval;
> > + u32 metadata_ratio;
> > + u32 thread_pool_size;
> > + unsigned long mount_opt;
> > + unsigned long compress_type:4;
> > + unsigned int compress_level;
> > +};
> > +
> > enum {
> > Opt_acl, Opt_noacl,
> > Opt_clear_cache,
> > @@ -348,6 +361,379 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] __maybe_unused = {
> > {}
> > };
> >
> > +static int btrfs_parse_param(struct fs_context *fc,
> > + struct fs_parameter *param)
> > +{
> > + struct btrfs_fs_context *ctx = fc->fs_private;
> > + struct fs_parse_result result;
> > + int opt;
> > +
> > + opt = fs_parse(fc, btrfs_fs_parameters, param, &result);
> > + if (opt < 0)
> > + return opt;
> > +
> > + switch (opt) {
> > + case Opt_degraded:
> > + btrfs_set_opt(ctx->mount_opt, DEGRADED);
> > + break;
> > + case Opt_subvol_empty:
> > + /*
> > + * This exists because we used to allow it on accident, so we're
> > + * keeping it to maintain ABI. See
> > + * 37becec95ac31b209eb1c8e096f1093a7db00f32.
>
> Please use the full patch reference 37becec95ac3 ("Btrfs: allow empty
> subvol= again"), the subject itself explains why it's here.
>
> > + */
> > + break;
> > + case Opt_subvol:
> > + kfree(ctx->subvol_name);
> > + ctx->subvol_name = kstrdup(param->string, GFP_KERNEL);
> > + if (!ctx->subvol_name)
> > + return -ENOMEM;
> > + break;
> > + case Opt_subvolid:
> > + ctx->subvol_objectid = result.uint_64;
> > +
> > + /* subvoldi=0 means give me the original fs_tree. */
>
> subvolid=0
>
> > + if (!ctx->subvol_objectid)
> > + ctx->subvol_objectid = BTRFS_FS_TREE_OBJECTID;
> > + break;
> > + case Opt_device: {
> > + struct btrfs_device *device;
> > + blk_mode_t mode = sb_open_mode(fc->sb_flags);
> > +
> > + mutex_lock(&uuid_mutex);
> > + device = btrfs_scan_one_device(param->string, mode, false);
> > + mutex_unlock(&uuid_mutex);
>
> So this changes how the device option and scan works. At this point the
> option is in the simple lock/unlock sequence, while currently it's
> scanning all devices under in one lock and then also opens all the
> devices. This prevents any other scan to interrupt that so it's either
> scanned right before (and filling the list) or after (which is a no-op).
>
> Now it's open to the races, I haven't evaluated if this could be a
> problem or not.
>

Udev has been scanning our devices ahead of time for years, this is exactly how
it exists currently. I don't think anybody is actually using -o
device=<whatever>, but if they are this gives them the same behavior that most
people get with the udev rule and mount /dev/oneofthedisks /foo.

If we're really worried about it however I could allocate the strings and attach
them to the context here, and then at mount time scan them all to give us the
same behavior as we had before.

> > + if (IS_ERR(device))
> > + return PTR_ERR(device);
> > + break;
> > + }
> > + case Opt_datasum:
> > + if (result.negated) {
> > + btrfs_set_opt(ctx->mount_opt, NODATASUM);
> > + } else {
> > + btrfs_clear_opt(ctx->mount_opt, NODATACOW);
> > + btrfs_clear_opt(ctx->mount_opt, NODATASUM);
> > + }
> > + break;
> > + case Opt_datacow:
> > + if (result.negated) {
> > + btrfs_clear_opt(ctx->mount_opt, COMPRESS);
> > + btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
> > + btrfs_set_opt(ctx->mount_opt, NODATACOW);
> > + btrfs_set_opt(ctx->mount_opt, NODATASUM);
> > + } else {
> > + btrfs_clear_opt(ctx->mount_opt, NODATACOW);
> > + }
> > + break;
> > + case Opt_compress_force:
> > + case Opt_compress_force_type:
> > + btrfs_set_opt(ctx->mount_opt, FORCE_COMPRESS);
> > + fallthrough;
> > + case Opt_compress:
> > + case Opt_compress_type:
> > + if (opt == Opt_compress ||
> > + opt == Opt_compress_force ||
> > + strncmp(param->string, "zlib", 4) == 0) {
> > + ctx->compress_type = BTRFS_COMPRESS_ZLIB;
> > + ctx->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
> > + /*
> > + * args[0] contains uninitialized data since
> > + * for these tokens we don't expect any
> > + * parameter.
> > + */
>
> Please reformat/realign comments that you copy or move
>
> > + if (opt != Opt_compress &&
> > + opt != Opt_compress_force)
> > + ctx->compress_level =
> > + btrfs_compress_str2level(
> > + BTRFS_COMPRESS_ZLIB,
> > + param->string + 4);
>
> This does not need to do newline after "("
>
> > + btrfs_set_opt(ctx->mount_opt, COMPRESS);
> > + btrfs_clear_opt(ctx->mount_opt, NODATACOW);
> > + btrfs_clear_opt(ctx->mount_opt, NODATASUM);
> > + } else if (strncmp(param->string, "lzo", 3) == 0) {
> > + ctx->compress_type = BTRFS_COMPRESS_LZO;
> > + ctx->compress_level = 0;
> > + btrfs_set_opt(ctx->mount_opt, COMPRESS);
> > + btrfs_clear_opt(ctx->mount_opt, NODATACOW);
> > + btrfs_clear_opt(ctx->mount_opt, NODATASUM);
> > + } else if (strncmp(param->string, "zstd", 4) == 0) {
> > + ctx->compress_type = BTRFS_COMPRESS_ZSTD;
> > + ctx->compress_level =
> > + btrfs_compress_str2level(
> > + BTRFS_COMPRESS_ZSTD,
> > + param->string + 4);
>
> Same
>
> > + btrfs_set_opt(ctx->mount_opt, COMPRESS);
> > + btrfs_clear_opt(ctx->mount_opt, NODATACOW);
> > + btrfs_clear_opt(ctx->mount_opt, NODATASUM);
> > + } else if (strncmp(param->string, "no", 2) == 0) {
> > + ctx->compress_level = 0;
> > + ctx->compress_type = 0;
> > + btrfs_clear_opt(ctx->mount_opt, COMPRESS);
> > + btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
> > + } else {
> > + btrfs_err(NULL, "unrecognized compression value %s",
> > + param->string);
> > + return -EINVAL;
> > + }
> > + break;
> > + case Opt_ssd:
> > + if (result.negated) {
> > + btrfs_set_opt(ctx->mount_opt, NOSSD);
> > + btrfs_clear_opt(ctx->mount_opt, SSD);
> > + btrfs_clear_opt(ctx->mount_opt, SSD_SPREAD);
> > + } else {
> > + btrfs_set_opt(ctx->mount_opt, SSD);
> > + btrfs_clear_opt(ctx->mount_opt, NOSSD);
> > + }
> > + break;
> > + case Opt_ssd_spread:
> > + if (result.negated) {
> > + btrfs_clear_opt(ctx->mount_opt, SSD_SPREAD);
> > + } else {
> > + btrfs_set_opt(ctx->mount_opt, SSD);
> > + btrfs_set_opt(ctx->mount_opt, SSD_SPREAD);
> > + btrfs_clear_opt(ctx->mount_opt, NOSSD);
> > + }
> > + break;
> > + case Opt_barrier:
> > + if (result.negated)
> > + btrfs_set_opt(ctx->mount_opt, NOBARRIER);
> > + else
> > + btrfs_clear_opt(ctx->mount_opt, NOBARRIER);
> > + break;
> > + case Opt_thread_pool:
> > + if (result.uint_32 == 0) {
> > + btrfs_err(NULL, "invalid value 0 for thread_pool");
> > + return -EINVAL;
> > + }
> > + ctx->thread_pool_size = result.uint_32;
>
> It's not in current code but we should eventually clamp the value,
> num_online_cpus or similar.
>
> > + break;
> > + case Opt_max_inline:
> > + ctx->max_inline = memparse(param->string, NULL);
>
> This does not match, the max_inline value is adjusted as
>
> if (info->max_inline) {
> info->max_inline = min_t(u64,
> info->max_inline,
> info->sectorsize);
> }
>
> and it should be validated at the time we parse it, like other options.
>

We can't do that with the current scheme, tho I did miss clam'ing it. I've
added the clamping part to the patch where we flip over to using the new mount
API.

> > + break;
> > + case Opt_acl:
> > + if (result.negated) {
> > + fc->sb_flags &= ~SB_POSIXACL;
> > + } else {
> > +#ifdef CONFIG_BTRFS_FS_POSIX_ACL
> > + fc->sb_flags |= SB_POSIXACL;
> > +#else
> > + btrfs_err(NULL, "support for ACL not compiled in!");
> > + ret = -EINVAL;
> > + goto out;
> > +#endif
> > + }
> > + /*
> > + * VFS limits the ability to toggle ACL on and off via remount,
> > + * despite every file system allowing this. This seems to be an
> > + * oversight since we all do, but it'll fail if we're
> > + * remounting. So don't set the mask here, we'll check it in
> > + * btrfs_reconfigure and do the toggling ourselves.
> > + */
> > + if (fc->purpose != FS_CONTEXT_FOR_RECONFIGURE)
> > + fc->sb_flags_mask |= SB_POSIXACL;
> > + break;
> > + case Opt_treelog:
> > + if (result.negated)
> > + btrfs_set_opt(ctx->mount_opt, NOTREELOG);
> > + else
> > + btrfs_clear_opt(ctx->mount_opt, NOTREELOG);
> > + break;
> > + case Opt_recovery:
> > + /*
> > + * -o recovery used to be an alias for usebackuproot, and then
> > + * norecovery was an alias for nologreplay, hence the different
> > + * behaviors for negated and not.
> > + */
> > + if (result.negated) {
> > + btrfs_warn(NULL,
> > + "'norecovery' is deprecated, use 'rescue=nologreplay' instead");
> > + btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
> > + } else {
> > + btrfs_warn(NULL,
> > + "'recovery' is deprecated, use 'rescue=usebackuproot' instead");
> > + btrfs_set_opt(ctx->mount_opt, USEBACKUPROOT);
> > + }
> > + break;
> > + case Opt_nologreplay:
> > + btrfs_warn(NULL,
> > + "'nologreplay' is deprecated, use 'rescue=nologreplay' instead");
> > + btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
> > + break;
> > + case Opt_flushoncommit:
> > + if (result.negated)
> > + btrfs_clear_opt(ctx->mount_opt, FLUSHONCOMMIT);
> > + else
> > + btrfs_set_opt(ctx->mount_opt, FLUSHONCOMMIT);
> > + break;
> > + case Opt_ratio:
> > + ctx->metadata_ratio = result.uint_32;
> > + break;
> > + case Opt_discard:
> > + if (result.negated) {
> > + btrfs_clear_opt(ctx->mount_opt, DISCARD_SYNC);
> > + btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
> > + btrfs_set_opt(ctx->mount_opt, NODISCARD);
> > + } else {
> > + btrfs_set_opt(ctx->mount_opt, DISCARD_SYNC);
> > + btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
> > + }
> > + break;
> > + case Opt_discard_mode:
> > + switch (result.uint_32) {
> > + case Opt_discard_sync:
> > + btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
> > + btrfs_set_opt(ctx->mount_opt, DISCARD_SYNC);
> > + break;
> > + case Opt_discard_async:
> > + btrfs_clear_opt(ctx->mount_opt, DISCARD_SYNC);
> > + btrfs_set_opt(ctx->mount_opt, DISCARD_ASYNC);
> > + break;
> > + default:
> > + btrfs_err(NULL, "unrecognized discard mode value %s",
> > + param->key);
> > + return -EINVAL;
> > + }
> > + btrfs_clear_opt(ctx->mount_opt, NODISCARD);
> > + break;
> > + case Opt_space_cache:
> > + if (result.negated) {
> > + btrfs_set_opt(ctx->mount_opt, NOSPACECACHE);
> > + btrfs_clear_opt(ctx->mount_opt, SPACE_CACHE);
> > + btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
> > + } else {
> > + btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
> > + btrfs_set_opt(ctx->mount_opt, SPACE_CACHE);
> > + }
> > + break;
> > + case Opt_space_cache_version:
> > + switch (result.uint_32) {
> > + case Opt_space_cache_v1:
> > + btrfs_set_opt(ctx->mount_opt, SPACE_CACHE);
> > + btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
> > + break;
> > + case Opt_space_cache_v2:
> > + btrfs_clear_opt(ctx->mount_opt, SPACE_CACHE);
> > + btrfs_set_opt(ctx->mount_opt, FREE_SPACE_TREE);
> > + break;
> > + default:
> > + btrfs_err(NULL, "unrecognized space_cache value %s",
> > + param->key);
> > + return -EINVAL;
> > + }
> > + break;
> > + case Opt_rescan_uuid_tree:
> > + btrfs_set_opt(ctx->mount_opt, RESCAN_UUID_TREE);
> > + break;
> > + case Opt_inode_cache:
> > + btrfs_warn(NULL,
> > + "the 'inode_cache' option is deprecated and has no effect since 5.11");
> > + break;
> > + case Opt_clear_cache:
> > + btrfs_set_opt(ctx->mount_opt, CLEAR_CACHE);
> > + break;
> > + case Opt_user_subvol_rm_allowed:
> > + btrfs_set_opt(ctx->mount_opt, USER_SUBVOL_RM_ALLOWED);
> > + break;
> > + case Opt_enospc_debug:
> > + if (result.negated)
> > + btrfs_clear_opt(ctx->mount_opt, ENOSPC_DEBUG);
> > + else
> > + btrfs_set_opt(ctx->mount_opt, ENOSPC_DEBUG);
> > + break;
> > + case Opt_defrag:
> > + if (result.negated)
> > + btrfs_clear_opt(ctx->mount_opt, AUTO_DEFRAG);
> > + else
> > + btrfs_set_opt(ctx->mount_opt, AUTO_DEFRAG);
> > + break;
> > + case Opt_usebackuproot:
> > + btrfs_warn(NULL,
> > + "'usebackuproot' is deprecated, use 'rescue=usebackuproot' instead");
> > + btrfs_set_opt(ctx->mount_opt, USEBACKUPROOT);
> > + break;
> > + case Opt_skip_balance:
> > + btrfs_set_opt(ctx->mount_opt, SKIP_BALANCE);
> > + break;
> > + case Opt_fatal_errors:
> > + switch (result.uint_32) {
> > + case Opt_fatal_errors_panic:
> > + btrfs_set_opt(ctx->mount_opt,
> > + PANIC_ON_FATAL_ERROR);
>
> Lines can be joined
>
> > + break;
> > + case Opt_fatal_errors_bug:
> > + btrfs_clear_opt(ctx->mount_opt,
> > + PANIC_ON_FATAL_ERROR);
>
> Same
>
> > + break;
> > + default:
> > + btrfs_err(NULL, "unrecognized fatal_errors value %s",
> > + param->key);
> > + return -EINVAL;
> > + }
> > + break;
> > + case Opt_commit_interval:
> > + ctx->commit_interval = result.uint_32;
> > + if (!ctx->commit_interval)
> > + ctx->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
>
> And the value of commit_interval is also adjusted in current code, this
> should be done here as well.
>

It isn't adjusted, we just yell if it's above 300. If you do -o
commit_interval=0 it wants the default interval, which is what I've handled
here. Thanks,

Josef