On Tue, Aug 26, 2025 at 10:12 PM André Almeida <andrealmeid@xxxxxxxxxx> wrote:
>
>
>
> Em 25/08/2025 12:32, Amir Goldstein escreveu:
> > On Mon, Aug 25, 2025 at 1:17 PM Gabriel Krisman Bertazi
> > <gabriel@xxxxxxxxxx> wrote:
> >>
> >> André Almeida <andrealmeid@xxxxxxxxxx> writes:
> >>
> >>> When merging layers from different filesystems with casefold enabled,
> >>> all layers should use the same encoding version and have the same flags
> >>> to avoid any kind of incompatibility issues.
> >>>
> >>> Also, set the encoding and the encoding flags for the ovl super block as
> >>> the same as used by the first valid layer.
> >>>
> >>> Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> >>> Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx>
> >>> ---
> >>> fs/overlayfs/super.c | 25 +++++++++++++++++++++++++
> >>> 1 file changed, 25 insertions(+)
> >>>
> >>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> >>> index df85a76597e910d00323018f1d2cd720c5db921d..b1dbd3c79961094d00c7f99cc622e515d544d22f 100644
> >>> --- a/fs/overlayfs/super.c
> >>> +++ b/fs/overlayfs/super.c
> >>> @@ -991,6 +991,18 @@ static int ovl_get_data_fsid(struct ovl_fs *ofs)
> >>> return ofs->numfs;
> >>> }
> >>>
> >>> +/*
> >>> + * Set the ovl sb encoding as the same one used by the first layer
> >>> + */
> >>> +static void ovl_set_encoding(struct super_block *sb, struct super_block *fs_sb)
> >>> +{
> >>> +#if IS_ENABLED(CONFIG_UNICODE)
> >>> + if (sb_has_encoding(fs_sb)) {
> >>> + sb->s_encoding = fs_sb->s_encoding;
> >>> + sb->s_encoding_flags = fs_sb->s_encoding_flags;
> >>> + }
> >>> +#endif
> >>> +}
> >>>
> >>> static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
> >>> struct ovl_fs_context *ctx, struct ovl_layer *layers)
> >>> @@ -1024,6 +1036,9 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
> >>> if (ovl_upper_mnt(ofs)) {
> >>> ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
> >>> ofs->fs[0].is_lower = false;
> >>> +
> >>> + if (ofs->casefold)
> >>> + ovl_set_encoding(sb, ofs->fs[0].sb);
> >>> }
> >>>
> >>> nr_merged_lower = ctx->nr - ctx->nr_data;
> >>> @@ -1083,6 +1098,16 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
> >>> l->name = NULL;
> >>> ofs->numlayer++;
> >>> ofs->fs[fsid].is_lower = true;
> >>> +
> >>> + if (ofs->casefold) {
> >>> + if (!ovl_upper_mnt(ofs) && !sb_has_encoding(sb))
> >>> + ovl_set_encoding(sb, ofs->fs[fsid].sb);
> >>> +
> >>> + if (!sb_has_encoding(sb) || !sb_same_encoding(sb, mnt->mnt_sb)) {
> >>
> >> Minor nit, but isn't the sb_has_encoding() check redundant here? sb_same_encoding
> >> will check the sb->encoding matches the mnt_sb already.
> >
> > Maybe we did something wrong but the intention was:
> > If all layers root are casefold disabled (or not supported) then
> > a mix of layers with fs of different encoding (and fs with no encoding support)
> > is allowed because we take care that all directories are always
> > casefold disabled.
> >
>
> We are going to reach this code only if ofs->casefold is true, so that
> means that ovl_dentry_casefolded() was true, and that means that
> sb_has_encoding(dentry->d_sb) is also true... so I think that Gabriel is
> right, if we reach this part of the code, that means that casefold is
> enabled and being used by at least one layer, so we can call
> sb_same_encoding() to check if they are consistent for all layers.
>
> For the case that we don't care about the layers having different
> encoding, the code will already skip this because of if (ofs->casefold)
Doh! yeh that was silly. I removed that now.
Thanks,
Amir.
