To add overlayfs support casefold layers, create a new function
ovl_casefold(), to be able to do case-insensitive strncmp().
ovl_casefold() allocates a new buffer and stores the casefolded version
of the string on it. If the allocation or the casefold operation fails,
fallback to use the original string.
The case-insentive name is then used in the rb-tree search/insertion
operation. If the name is found in the rb-tree, the name can be
discarded and the buffer is freed. If the name isn't found, it's then
stored at struct ovl_cache_entry to be used later.
Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
Changes from v4:
- Move the consumer/free buffer logic out to the caller
- s/aux/c_name
Changes from v3:
- Improve commit message text
- s/OVL_NAME_LEN/NAME_MAX
- drop #ifdef in favor of if(IS_ENABLED)
- use new helper sb_encoding
- merged patch "Store casefold name..." and "Create ovl_casefold()..."
- Guard all the casefolding inside of IS_ENABLED(UNICODE)
Changes from v2:
- Refactor the patch to do a single kmalloc() per rb_tree operation
- Instead of casefolding the cache entry name everytime per strncmp(),
casefold it once and reuse it for every strncmp().
---
fs/overlayfs/readdir.c | 115 +++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 97 insertions(+), 18 deletions(-)
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index b65cdfce31ce27172d28d879559f1008b9c87320..803ac6a7516d0156ae7793ee1ff884dbbf2e20b0 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -27,6 +27,8 @@ struct ovl_cache_entry {
bool is_upper;
bool is_whiteout;
bool check_xwhiteout;
+ const char *cf_name;
+ int cf_len;
char name[];
};
@@ -45,6 +47,7 @@ struct ovl_readdir_data {
struct list_head *list;
struct list_head middle;
struct ovl_cache_entry *first_maybe_whiteout;
+ struct unicode_map *map;
int count;
int err;
bool is_upper;
@@ -66,6 +69,27 @@ static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
return rb_entry(n, struct ovl_cache_entry, node);
}
+static int ovl_casefold(struct unicode_map *map, const char *str, int len, char **dst)
+{
+ const struct qstr qstr = { .name = str, .len = len };
+ int cf_len;
+
+ if (!IS_ENABLED(CONFIG_UNICODE) || !map || is_dot_dotdot(str, len))
+ return 0;
+
+ *dst = kmalloc(NAME_MAX, GFP_KERNEL);
+
+ if (dst) {
+ cf_len = utf8_casefold(map, &qstr, *dst, NAME_MAX);
+
+ if (cf_len > 0)
+ return cf_len;
+ }
+
+ kfree(*dst);
+ return 0;
+}
+
static bool ovl_cache_entry_find_link(const char *name, int len,
struct rb_node ***link,
struct rb_node **parent)
@@ -79,7 +103,7 @@ static bool ovl_cache_entry_find_link(const char *name, int len,
*parent = *newp;
tmp = ovl_cache_entry_from_node(*newp);
- cmp = strncmp(name, tmp->name, len);
+ cmp = strncmp(name, tmp->cf_name, tmp->cf_len);
if (cmp > 0)
newp = &tmp->node.rb_right;
else if (cmp < 0 || len < tmp->len)
@@ -101,7 +125,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
while (node) {
struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
- cmp = strncmp(name, p->name, len);
+ cmp = strncmp(name, p->cf_name, p->cf_len);
if (cmp > 0)
node = p->node.rb_right;
else if (cmp < 0 || len < p->len)
@@ -145,13 +169,16 @@ static bool ovl_calc_d_ino(struct ovl_readdir_data *rdd,
static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
const char *name, int len,
+ const char *cf_name, int cf_len,
u64 ino, unsigned int d_type)
{
struct ovl_cache_entry *p;
p = kmalloc(struct_size(p, name, len + 1), GFP_KERNEL);
- if (!p)
+ if (!p) {
+ kfree(cf_name);
return NULL;
+ }
memcpy(p->name, name, len);
p->name[len] = '\0';
@@ -167,6 +194,14 @@ static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
/* Defer check for overlay.whiteout to ovl_iterate() */
p->check_xwhiteout = rdd->in_xwhiteouts_dir && d_type == DT_REG;
+ if (cf_name && cf_name != name) {
+ p->cf_name = cf_name;
+ p->cf_len = cf_len;
+ } else {
+ p->cf_name = p->name;
+ p->cf_len = len;
+ }
+
if (d_type == DT_CHR) {
p->next_maybe_whiteout = rdd->first_maybe_whiteout;
rdd->first_maybe_whiteout = p;
@@ -174,48 +209,55 @@ static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
return p;
}
-static bool ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
- const char *name, int len, u64 ino,
+/* Return 0 for found, 1 for added, <0 for error */
+static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
+ const char *name, int len,
+ const char *cf_name, int cf_len,
+ u64 ino,
unsigned int d_type)
{
struct rb_node **newp = &rdd->root->rb_node;
struct rb_node *parent = NULL;
struct ovl_cache_entry *p;
- if (ovl_cache_entry_find_link(name, len, &newp, &parent))
- return true;
+ if (ovl_cache_entry_find_link(cf_name, cf_len, &newp, &parent))
+ return 0;
- p = ovl_cache_entry_new(rdd, name, len, ino, d_type);
+ p = ovl_cache_entry_new(rdd, name, len, cf_name, cf_len, ino, d_type);
if (p == NULL) {
rdd->err = -ENOMEM;
- return false;
+ return -ENOMEM;
}
list_add_tail(&p->l_node, rdd->list);
rb_link_node(&p->node, parent, newp);
rb_insert_color(&p->node, rdd->root);
- return true;
+ return 1;
}
-static bool ovl_fill_lowest(struct ovl_readdir_data *rdd,
+/* Return 0 for found, 1 for added, <0 for error */
+static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
const char *name, int namelen,
+ const char *cf_name, int cf_len,
loff_t offset, u64 ino, unsigned int d_type)
{
struct ovl_cache_entry *p;
- p = ovl_cache_entry_find(rdd->root, name, namelen);
+ p = ovl_cache_entry_find(rdd->root, cf_name, cf_len);
if (p) {
list_move_tail(&p->l_node, &rdd->middle);
+ return 0;
} else {
- p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
+ p = ovl_cache_entry_new(rdd, name, namelen, cf_name, cf_len,
+ ino, d_type);
if (p == NULL)
rdd->err = -ENOMEM;
else
list_add_tail(&p->l_node, &rdd->middle);
}
- return rdd->err == 0;
+ return rdd->err ?: 1;
}
void ovl_cache_free(struct list_head *list)
@@ -223,8 +265,11 @@ void ovl_cache_free(struct list_head *list)
struct ovl_cache_entry *p;
struct ovl_cache_entry *n;
- list_for_each_entry_safe(p, n, list, l_node)
+ list_for_each_entry_safe(p, n, list, l_node) {
+ if (p->cf_name != p->name)
+ kfree(p->cf_name);
kfree(p);
+ }
INIT_LIST_HEAD(list);
}
@@ -260,12 +305,38 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
{
struct ovl_readdir_data *rdd =
container_of(ctx, struct ovl_readdir_data, ctx);
+ struct ovl_fs *ofs = OVL_FS(rdd->dentry->d_sb);
+ char *cf_name = NULL;
+ int c_len = 0;
+ int ret;
+
+ const char *c_name = NULL;
+
+ if (ofs->casefold)
+ c_len = ovl_casefold(rdd->map, name, namelen, &cf_name);
+
+ if (c_len <= 0) {
+ c_name = name;
+ c_len = namelen;
+ } else {
+ c_name = cf_name;
+ }
rdd->count++;
if (!rdd->is_lowest)
- return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
+ ret = ovl_cache_entry_add_rb(rdd, name, namelen, c_name, c_len, ino, d_type);
else
- return ovl_fill_lowest(rdd, name, namelen, offset, ino, d_type);
+ ret = ovl_fill_lowest(rdd, name, namelen, c_name, c_len, offset, ino, d_type);
+
+ /*
+ * If ret == 1, that means that c_name is being used as part of struct
+ * ovl_cache_entry and will be freed at ovl_cache_free(). Otherwise,
+ * c_name was found in the rb-tree so we can free it here.
+ */
+ if (ret != 1 && c_name != name)
+ kfree(c_name);
+
+ return ret >= 0;
}
static int ovl_check_whiteouts(const struct path *path, struct ovl_readdir_data *rdd)
@@ -357,12 +428,18 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list,
.list = list,
.root = root,
.is_lowest = false,
+ .map = NULL,
};
int idx, next;
const struct ovl_layer *layer;
+ struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
for (idx = 0; idx != -1; idx = next) {
next = ovl_path_next(idx, dentry, &realpath, &layer);
+
+ if (ofs->casefold)
+ rdd.map = sb_encoding(realpath.dentry->d_sb);
+
rdd.is_upper = ovl_dentry_upper(dentry) == realpath.dentry;
rdd.in_xwhiteouts_dir = layer->has_xwhiteouts &&
ovl_dentry_has_xwhiteouts(dentry);
@@ -555,7 +632,7 @@ static bool ovl_fill_plain(struct dir_context *ctx, const char *name,
container_of(ctx, struct ovl_readdir_data, ctx);
rdd->count++;
- p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
+ p = ovl_cache_entry_new(rdd, name, namelen, NULL, 0, ino, d_type);
if (p == NULL) {
rdd->err = -ENOMEM;
return false;
@@ -1023,6 +1100,8 @@ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
del_entry:
list_del(&p->l_node);
+ if (p->cf_name != p->name)
+ kfree(p->cf_name);
kfree(p);
}
--
2.50.1
On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>
> To add overlayfs support casefold layers, create a new function
> ovl_casefold(), to be able to do case-insensitive strncmp().
>
> ovl_casefold() allocates a new buffer and stores the casefolded version
> of the string on it. If the allocation or the casefold operation fails,
> fallback to use the original string.
>
> The case-insentive name is then used in the rb-tree search/insertion
> operation. If the name is found in the rb-tree, the name can be
> discarded and the buffer is freed. If the name isn't found, it's then
> stored at struct ovl_cache_entry to be used later.
>
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
> Changes from v4:
> - Move the consumer/free buffer logic out to the caller
> - s/aux/c_name
>
> Changes from v3:
> - Improve commit message text
> - s/OVL_NAME_LEN/NAME_MAX
> - drop #ifdef in favor of if(IS_ENABLED)
> - use new helper sb_encoding
> - merged patch "Store casefold name..." and "Create ovl_casefold()..."
> - Guard all the casefolding inside of IS_ENABLED(UNICODE)
>
> Changes from v2:
> - Refactor the patch to do a single kmalloc() per rb_tree operation
> - Instead of casefolding the cache entry name everytime per strncmp(),
> casefold it once and reuse it for every strncmp().
> ---
> fs/overlayfs/readdir.c | 115 +++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 97 insertions(+), 18 deletions(-)
>
> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
> index b65cdfce31ce27172d28d879559f1008b9c87320..803ac6a7516d0156ae7793ee1ff884dbbf2e20b0 100644
> --- a/fs/overlayfs/readdir.c
> +++ b/fs/overlayfs/readdir.c
> @@ -27,6 +27,8 @@ struct ovl_cache_entry {
> bool is_upper;
> bool is_whiteout;
> bool check_xwhiteout;
> + const char *cf_name;
> + int cf_len;
We should also change these member names to c_name
Because they are the "compare/canonicalized" name, which
may or may not be casefolded.
> char name[];
> };
>
> @@ -45,6 +47,7 @@ struct ovl_readdir_data {
> struct list_head *list;
> struct list_head middle;
> struct ovl_cache_entry *first_maybe_whiteout;
> + struct unicode_map *map;
> int count;
> int err;
> bool is_upper;
> @@ -66,6 +69,27 @@ static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
> return rb_entry(n, struct ovl_cache_entry, node);
> }
>
> +static int ovl_casefold(struct unicode_map *map, const char *str, int len, char **dst)
> +{
> + const struct qstr qstr = { .name = str, .len = len };
> + int cf_len;
> +
> + if (!IS_ENABLED(CONFIG_UNICODE) || !map || is_dot_dotdot(str, len))
> + return 0;
> +
> + *dst = kmalloc(NAME_MAX, GFP_KERNEL);
> +
> + if (dst) {
> + cf_len = utf8_casefold(map, &qstr, *dst, NAME_MAX);
> +
> + if (cf_len > 0)
> + return cf_len;
> + }
> +
> + kfree(*dst);
> + return 0;
> +}
> +
> static bool ovl_cache_entry_find_link(const char *name, int len,
> struct rb_node ***link,
> struct rb_node **parent)
> @@ -79,7 +103,7 @@ static bool ovl_cache_entry_find_link(const char *name, int len,
>
> *parent = *newp;
> tmp = ovl_cache_entry_from_node(*newp);
> - cmp = strncmp(name, tmp->name, len);
> + cmp = strncmp(name, tmp->cf_name, tmp->cf_len);
> if (cmp > 0)
> newp = &tmp->node.rb_right;
> else if (cmp < 0 || len < tmp->len)
This looks like a bug - should be len < tmp->c_len
> @@ -101,7 +125,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
> while (node) {
> struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
>
> - cmp = strncmp(name, p->name, len);
> + cmp = strncmp(name, p->cf_name, p->cf_len);
> if (cmp > 0)
> node = p->node.rb_right;
> else if (cmp < 0 || len < p->len)
Same here.
But it's not the only bug, because this patch regresses 3 fstests without
enabling any casefolding:
overlay/038 12s ... [14:16:39] [14:16:50]- output mismatch (see
/results/overlay/results-large/overlay/038.out.bad)
--- tests/overlay/038.out 2025-05-25 08:52:54.000000000 +0000
+++ /results/overlay/results-large/overlay/038.out.bad 2025-08-17
14:16:50.549367654 +0000
@@ -1,2 +1,3 @@
QA output created by 038
+Merged dir: Invalid d_ino reported for ..
Silence is golden
overlay/041 11s ... [14:16:54] [14:17:05]- output mismatch (see
/results/overlay/results-large/overlay/041.out.bad)
--- tests/overlay/041.out 2025-05-25 08:52:54.000000000 +0000
+++ /results/overlay/results-large/overlay/041.out.bad 2025-08-17
14:17:05.275206922 +0000
@@ -1,2 +1,3 @@
QA output created by 041
+Merged dir: Invalid d_ino reported for ..
Silence is golden
overlay/077 19s ... [14:17:08][ 107.348626] WARNING: CPU: 3 PID:
5414 at fs/overlayfs/readdir.c:677 ovl_dir_read_impure+0x178/0x1c0
[ 107.354647] ---[ end trace 0000000000000000 ]---
[ 107.399525] WARNING: CPU: 2 PID: 5415 at fs/overlayfs/readdir.c:677
ovl_dir_read_impure+0x178/0x1c0
[ 107.406826] ---[ end trace 0000000000000000 ]---
_check_dmesg: something found in dmesg (see
/results/overlay/results-large/overlay/077.dmesg)
[14:17:28]- output mismatch (see
/results/overlay/results-large/overlay/077.out.bad)
--- tests/overlay/077.out 2025-05-25 08:52:54.000000000 +0000
+++ /results/overlay/results-large/overlay/077.out.bad 2025-08-17
14:17:28.762250671 +0000
@@ -1,2 +1,6 @@
QA output created by 077
+getdents: Input/output error
+Missing created file in impure upper dir (see
/results/overlay/results-large/overlay/077.full for details)
+getdents: Input/output error
+Found unlinked file in impure upper dir (see
/results/overlay/results-large/overlay/077.full for details)
Silence is golden
Thanks,
Amir.
Em 17/08/2025 11:33, Amir Goldstein escreveu:
> On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>>
>> To add overlayfs support casefold layers, create a new function
>> ovl_casefold(), to be able to do case-insensitive strncmp().
>>
>> ovl_casefold() allocates a new buffer and stores the casefolded version
>> of the string on it. If the allocation or the casefold operation fails,
>> fallback to use the original string.
>>
>> The case-insentive name is then used in the rb-tree search/insertion
>> operation. If the name is found in the rb-tree, the name can be
>> discarded and the buffer is freed. If the name isn't found, it's then
>> stored at struct ovl_cache_entry to be used later.
>>
>> Signed-off-by: André Almeida <andrealmeid@igalia.com>
>> ---
>> Changes from v4:
>> - Move the consumer/free buffer logic out to the caller
>> - s/aux/c_name
>>
>> Changes from v3:
>> - Improve commit message text
>> - s/OVL_NAME_LEN/NAME_MAX
>> - drop #ifdef in favor of if(IS_ENABLED)
>> - use new helper sb_encoding
>> - merged patch "Store casefold name..." and "Create ovl_casefold()..."
>> - Guard all the casefolding inside of IS_ENABLED(UNICODE)
>>
>> Changes from v2:
>> - Refactor the patch to do a single kmalloc() per rb_tree operation
>> - Instead of casefolding the cache entry name everytime per strncmp(),
>> casefold it once and reuse it for every strncmp().
>> ---
>> fs/overlayfs/readdir.c | 115 +++++++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 97 insertions(+), 18 deletions(-)
>>
>> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
>> index b65cdfce31ce27172d28d879559f1008b9c87320..803ac6a7516d0156ae7793ee1ff884dbbf2e20b0 100644
>> --- a/fs/overlayfs/readdir.c
>> +++ b/fs/overlayfs/readdir.c
>> @@ -27,6 +27,8 @@ struct ovl_cache_entry {
>> bool is_upper;
>> bool is_whiteout;
>> bool check_xwhiteout;
>> + const char *cf_name;
>> + int cf_len;
>
> We should also change these member names to c_name
> Because they are the "compare/canonicalized" name, which
> may or may not be casefolded.
>
>> char name[];
>> };
>>
>> @@ -45,6 +47,7 @@ struct ovl_readdir_data {
>> struct list_head *list;
>> struct list_head middle;
>> struct ovl_cache_entry *first_maybe_whiteout;
>> + struct unicode_map *map;
>> int count;
>> int err;
>> bool is_upper;
>> @@ -66,6 +69,27 @@ static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
>> return rb_entry(n, struct ovl_cache_entry, node);
>> }
>>
>> +static int ovl_casefold(struct unicode_map *map, const char *str, int len, char **dst)
>> +{
>> + const struct qstr qstr = { .name = str, .len = len };
>> + int cf_len;
>> +
>> + if (!IS_ENABLED(CONFIG_UNICODE) || !map || is_dot_dotdot(str, len))
>> + return 0;
>> +
>> + *dst = kmalloc(NAME_MAX, GFP_KERNEL);
>> +
>> + if (dst) {
>> + cf_len = utf8_casefold(map, &qstr, *dst, NAME_MAX);
>> +
>> + if (cf_len > 0)
>> + return cf_len;
>> + }
>> +
>> + kfree(*dst);
>> + return 0;
>> +}
>> +
>> static bool ovl_cache_entry_find_link(const char *name, int len,
>> struct rb_node ***link,
>> struct rb_node **parent)
>> @@ -79,7 +103,7 @@ static bool ovl_cache_entry_find_link(const char *name, int len,
>>
>> *parent = *newp;
>> tmp = ovl_cache_entry_from_node(*newp);
>> - cmp = strncmp(name, tmp->name, len);
>> + cmp = strncmp(name, tmp->cf_name, tmp->cf_len);
>> if (cmp > 0)
>> newp = &tmp->node.rb_right;
>> else if (cmp < 0 || len < tmp->len)
>
> This looks like a bug - should be len < tmp->c_len
>
>> @@ -101,7 +125,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
>> while (node) {
>> struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
>>
>> - cmp = strncmp(name, p->name, len);
>> + cmp = strncmp(name, p->cf_name, p->cf_len);
>> if (cmp > 0)
>> node = p->node.rb_right;
>> else if (cmp < 0 || len < p->len)
>
> Same here.
>
> But it's not the only bug, because this patch regresses 3 fstests without
> enabling any casefolding:
>
That was due to the following change:
- cmp = strncmp(name, p->name, len);
+ cmp = strncmp(name, p->cf_name, p->cf_len);
Keeping len (instead of p->cf_len) as the third argument fixed it. I
will send a v6 with that and the other changes.
> overlay/038 12s ... [14:16:39] [14:16:50]- output mismatch (see
> /results/overlay/results-large/overlay/038.out.bad)
> --- tests/overlay/038.out 2025-05-25 08:52:54.000000000 +0000
> +++ /results/overlay/results-large/overlay/038.out.bad 2025-08-17
> 14:16:50.549367654 +0000
> @@ -1,2 +1,3 @@
> QA output created by 038
> +Merged dir: Invalid d_ino reported for ..
> Silence is golden
>
> overlay/041 11s ... [14:16:54] [14:17:05]- output mismatch (see
> /results/overlay/results-large/overlay/041.out.bad)
> --- tests/overlay/041.out 2025-05-25 08:52:54.000000000 +0000
> +++ /results/overlay/results-large/overlay/041.out.bad 2025-08-17
> 14:17:05.275206922 +0000
> @@ -1,2 +1,3 @@
> QA output created by 041
> +Merged dir: Invalid d_ino reported for ..
> Silence is golden
>
> overlay/077 19s ... [14:17:08][ 107.348626] WARNING: CPU: 3 PID:
> 5414 at fs/overlayfs/readdir.c:677 ovl_dir_read_impure+0x178/0x1c0
> [ 107.354647] ---[ end trace 0000000000000000 ]---
> [ 107.399525] WARNING: CPU: 2 PID: 5415 at fs/overlayfs/readdir.c:677
> ovl_dir_read_impure+0x178/0x1c0
> [ 107.406826] ---[ end trace 0000000000000000 ]---
> _check_dmesg: something found in dmesg (see
> /results/overlay/results-large/overlay/077.dmesg)
> [14:17:28]- output mismatch (see
> /results/overlay/results-large/overlay/077.out.bad)
> --- tests/overlay/077.out 2025-05-25 08:52:54.000000000 +0000
> +++ /results/overlay/results-large/overlay/077.out.bad 2025-08-17
> 14:17:28.762250671 +0000
> @@ -1,2 +1,6 @@
> QA output created by 077
> +getdents: Input/output error
> +Missing created file in impure upper dir (see
> /results/overlay/results-large/overlay/077.full for details)
> +getdents: Input/output error
> +Found unlinked file in impure upper dir (see
> /results/overlay/results-large/overlay/077.full for details)
> Silence is golden
>
> Thanks,
> Amir.
On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>
> To add overlayfs support casefold layers, create a new function
> ovl_casefold(), to be able to do case-insensitive strncmp().
>
> ovl_casefold() allocates a new buffer and stores the casefolded version
> of the string on it. If the allocation or the casefold operation fails,
> fallback to use the original string.
>
> The case-insentive name is then used in the rb-tree search/insertion
> operation. If the name is found in the rb-tree, the name can be
> discarded and the buffer is freed. If the name isn't found, it's then
> stored at struct ovl_cache_entry to be used later.
>
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
> Changes from v4:
> - Move the consumer/free buffer logic out to the caller
> - s/aux/c_name
>
> Changes from v3:
> - Improve commit message text
> - s/OVL_NAME_LEN/NAME_MAX
> - drop #ifdef in favor of if(IS_ENABLED)
> - use new helper sb_encoding
> - merged patch "Store casefold name..." and "Create ovl_casefold()..."
> - Guard all the casefolding inside of IS_ENABLED(UNICODE)
>
> Changes from v2:
> - Refactor the patch to do a single kmalloc() per rb_tree operation
> - Instead of casefolding the cache entry name everytime per strncmp(),
> casefold it once and reuse it for every strncmp().
> ---
> fs/overlayfs/readdir.c | 115 +++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 97 insertions(+), 18 deletions(-)
>
> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
> index b65cdfce31ce27172d28d879559f1008b9c87320..803ac6a7516d0156ae7793ee1ff884dbbf2e20b0 100644
> --- a/fs/overlayfs/readdir.c
> +++ b/fs/overlayfs/readdir.c
> @@ -27,6 +27,8 @@ struct ovl_cache_entry {
> bool is_upper;
> bool is_whiteout;
> bool check_xwhiteout;
> + const char *cf_name;
> + int cf_len;
> char name[];
> };
>
> @@ -45,6 +47,7 @@ struct ovl_readdir_data {
> struct list_head *list;
> struct list_head middle;
> struct ovl_cache_entry *first_maybe_whiteout;
> + struct unicode_map *map;
> int count;
> int err;
> bool is_upper;
> @@ -66,6 +69,27 @@ static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
> return rb_entry(n, struct ovl_cache_entry, node);
> }
>
> +static int ovl_casefold(struct unicode_map *map, const char *str, int len, char **dst)
> +{
> + const struct qstr qstr = { .name = str, .len = len };
> + int cf_len;
> +
> + if (!IS_ENABLED(CONFIG_UNICODE) || !map || is_dot_dotdot(str, len))
> + return 0;
> +
> + *dst = kmalloc(NAME_MAX, GFP_KERNEL);
> +
> + if (dst) {
> + cf_len = utf8_casefold(map, &qstr, *dst, NAME_MAX);
> +
> + if (cf_len > 0)
> + return cf_len;
> + }
> +
> + kfree(*dst);
> + return 0;
> +}
> +
> static bool ovl_cache_entry_find_link(const char *name, int len,
> struct rb_node ***link,
> struct rb_node **parent)
> @@ -79,7 +103,7 @@ static bool ovl_cache_entry_find_link(const char *name, int len,
>
> *parent = *newp;
> tmp = ovl_cache_entry_from_node(*newp);
> - cmp = strncmp(name, tmp->name, len);
> + cmp = strncmp(name, tmp->cf_name, tmp->cf_len);
> if (cmp > 0)
> newp = &tmp->node.rb_right;
> else if (cmp < 0 || len < tmp->len)
> @@ -101,7 +125,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
> while (node) {
> struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
>
> - cmp = strncmp(name, p->name, len);
> + cmp = strncmp(name, p->cf_name, p->cf_len);
> if (cmp > 0)
> node = p->node.rb_right;
> else if (cmp < 0 || len < p->len)
> @@ -145,13 +169,16 @@ static bool ovl_calc_d_ino(struct ovl_readdir_data *rdd,
>
> static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
> const char *name, int len,
> + const char *cf_name, int cf_len,
> u64 ino, unsigned int d_type)
> {
> struct ovl_cache_entry *p;
>
> p = kmalloc(struct_size(p, name, len + 1), GFP_KERNEL);
> - if (!p)
> + if (!p) {
> + kfree(cf_name);
> return NULL;
> + }
>
> memcpy(p->name, name, len);
> p->name[len] = '\0';
> @@ -167,6 +194,14 @@ static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
> /* Defer check for overlay.whiteout to ovl_iterate() */
> p->check_xwhiteout = rdd->in_xwhiteouts_dir && d_type == DT_REG;
>
> + if (cf_name && cf_name != name) {
> + p->cf_name = cf_name;
> + p->cf_len = cf_len;
> + } else {
> + p->cf_name = p->name;
> + p->cf_len = len;
> + }
> +
> if (d_type == DT_CHR) {
> p->next_maybe_whiteout = rdd->first_maybe_whiteout;
> rdd->first_maybe_whiteout = p;
> @@ -174,48 +209,55 @@ static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
> return p;
> }
>
> -static bool ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
> - const char *name, int len, u64 ino,
> +/* Return 0 for found, 1 for added, <0 for error */
> +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
> + const char *name, int len,
> + const char *cf_name, int cf_len,
> + u64 ino,
> unsigned int d_type)
> {
> struct rb_node **newp = &rdd->root->rb_node;
> struct rb_node *parent = NULL;
> struct ovl_cache_entry *p;
>
> - if (ovl_cache_entry_find_link(name, len, &newp, &parent))
> - return true;
> + if (ovl_cache_entry_find_link(cf_name, cf_len, &newp, &parent))
> + return 0;
>
> - p = ovl_cache_entry_new(rdd, name, len, ino, d_type);
> + p = ovl_cache_entry_new(rdd, name, len, cf_name, cf_len, ino, d_type);
> if (p == NULL) {
> rdd->err = -ENOMEM;
> - return false;
> + return -ENOMEM;
> }
>
> list_add_tail(&p->l_node, rdd->list);
> rb_link_node(&p->node, parent, newp);
> rb_insert_color(&p->node, rdd->root);
>
> - return true;
> + return 1;
> }
>
> -static bool ovl_fill_lowest(struct ovl_readdir_data *rdd,
> +/* Return 0 for found, 1 for added, <0 for error */
> +static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
> const char *name, int namelen,
> + const char *cf_name, int cf_len,
> loff_t offset, u64 ino, unsigned int d_type)
> {
> struct ovl_cache_entry *p;
>
> - p = ovl_cache_entry_find(rdd->root, name, namelen);
> + p = ovl_cache_entry_find(rdd->root, cf_name, cf_len);
> if (p) {
> list_move_tail(&p->l_node, &rdd->middle);
> + return 0;
> } else {
> - p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
> + p = ovl_cache_entry_new(rdd, name, namelen, cf_name, cf_len,
> + ino, d_type);
> if (p == NULL)
> rdd->err = -ENOMEM;
> else
> list_add_tail(&p->l_node, &rdd->middle);
> }
>
> - return rdd->err == 0;
> + return rdd->err ?: 1;
> }
>
> void ovl_cache_free(struct list_head *list)
> @@ -223,8 +265,11 @@ void ovl_cache_free(struct list_head *list)
> struct ovl_cache_entry *p;
> struct ovl_cache_entry *n;
>
> - list_for_each_entry_safe(p, n, list, l_node)
> + list_for_each_entry_safe(p, n, list, l_node) {
> + if (p->cf_name != p->name)
> + kfree(p->cf_name);
> kfree(p);
> + }
>
> INIT_LIST_HEAD(list);
> }
> @@ -260,12 +305,38 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
> {
> struct ovl_readdir_data *rdd =
> container_of(ctx, struct ovl_readdir_data, ctx);
> + struct ovl_fs *ofs = OVL_FS(rdd->dentry->d_sb);
> + char *cf_name = NULL;
> + int c_len = 0;
> + int ret;
> +
> + const char *c_name = NULL;
> +
Another nit:
Pls move up next to cf_name = NULL line in your branch
No need to repost.
Thanks,
Amir.
On 8/15/25 13:16, Amir Goldstein wrote:
> On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>> To add overlayfs support casefold layers, create a new function
>> ovl_casefold(), to be able to do case-insensitive strncmp().
>>
>> ovl_casefold() allocates a new buffer and stores the casefolded version
>> of the string on it. If the allocation or the casefold operation fails,
>> fallback to use the original string.
>>
>> The case-insentive name is then used in the rb-tree search/insertion
>> operation. If the name is found in the rb-tree, the name can be
>> discarded and the buffer is freed. If the name isn't found, it's then
>> stored at struct ovl_cache_entry to be used later.
>>
>> Signed-off-by: André Almeida <andrealmeid@igalia.com>
[...]
>> @@ -260,12 +305,38 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
>> {
>> struct ovl_readdir_data *rdd =
>> container_of(ctx, struct ovl_readdir_data, ctx);
>> + struct ovl_fs *ofs = OVL_FS(rdd->dentry->d_sb);
>> + char *cf_name = NULL;
>> + int c_len = 0;
>> + int ret;
>> +
>> + const char *c_name = NULL;
>> +
> Another nit:
> Pls move up next to cf_name = NULL line in your branch
>
> No need to repost.
Done. Also joined int ret and int c_len to the same declaration;
>
> Thanks,
> Amir.
On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@igalia.com> wrote:
>
> To add overlayfs support casefold layers, create a new function
> ovl_casefold(), to be able to do case-insensitive strncmp().
>
> ovl_casefold() allocates a new buffer and stores the casefolded version
> of the string on it. If the allocation or the casefold operation fails,
> fallback to use the original string.
>
> The case-insentive name is then used in the rb-tree search/insertion
> operation. If the name is found in the rb-tree, the name can be
> discarded and the buffer is freed. If the name isn't found, it's then
> stored at struct ovl_cache_entry to be used later.
>
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
> Changes from v4:
> - Move the consumer/free buffer logic out to the caller
> - s/aux/c_name
>
> Changes from v3:
> - Improve commit message text
> - s/OVL_NAME_LEN/NAME_MAX
> - drop #ifdef in favor of if(IS_ENABLED)
> - use new helper sb_encoding
> - merged patch "Store casefold name..." and "Create ovl_casefold()..."
> - Guard all the casefolding inside of IS_ENABLED(UNICODE)
>
> Changes from v2:
> - Refactor the patch to do a single kmalloc() per rb_tree operation
> - Instead of casefolding the cache entry name everytime per strncmp(),
> casefold it once and reuse it for every strncmp().
> ---
> fs/overlayfs/readdir.c | 115 +++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 97 insertions(+), 18 deletions(-)
>
> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
> index b65cdfce31ce27172d28d879559f1008b9c87320..803ac6a7516d0156ae7793ee1ff884dbbf2e20b0 100644
> --- a/fs/overlayfs/readdir.c
> +++ b/fs/overlayfs/readdir.c
> @@ -27,6 +27,8 @@ struct ovl_cache_entry {
> bool is_upper;
> bool is_whiteout;
> bool check_xwhiteout;
> + const char *cf_name;
> + int cf_len;
> char name[];
> };
>
> @@ -45,6 +47,7 @@ struct ovl_readdir_data {
> struct list_head *list;
> struct list_head middle;
> struct ovl_cache_entry *first_maybe_whiteout;
> + struct unicode_map *map;
> int count;
> int err;
> bool is_upper;
> @@ -66,6 +69,27 @@ static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
> return rb_entry(n, struct ovl_cache_entry, node);
> }
>
> +static int ovl_casefold(struct unicode_map *map, const char *str, int len, char **dst)
> +{
> + const struct qstr qstr = { .name = str, .len = len };
> + int cf_len;
> +
> + if (!IS_ENABLED(CONFIG_UNICODE) || !map || is_dot_dotdot(str, len))
> + return 0;
> +
> + *dst = kmalloc(NAME_MAX, GFP_KERNEL);
> +
> + if (dst) {
> + cf_len = utf8_casefold(map, &qstr, *dst, NAME_MAX);
> +
> + if (cf_len > 0)
> + return cf_len;
> + }
> +
> + kfree(*dst);
> + return 0;
> +}
> +
> static bool ovl_cache_entry_find_link(const char *name, int len,
> struct rb_node ***link,
> struct rb_node **parent)
> @@ -79,7 +103,7 @@ static bool ovl_cache_entry_find_link(const char *name, int len,
>
> *parent = *newp;
> tmp = ovl_cache_entry_from_node(*newp);
> - cmp = strncmp(name, tmp->name, len);
> + cmp = strncmp(name, tmp->cf_name, tmp->cf_len);
> if (cmp > 0)
> newp = &tmp->node.rb_right;
> else if (cmp < 0 || len < tmp->len)
> @@ -101,7 +125,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
> while (node) {
> struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
>
> - cmp = strncmp(name, p->name, len);
> + cmp = strncmp(name, p->cf_name, p->cf_len);
> if (cmp > 0)
> node = p->node.rb_right;
> else if (cmp < 0 || len < p->len)
> @@ -145,13 +169,16 @@ static bool ovl_calc_d_ino(struct ovl_readdir_data *rdd,
>
> static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
> const char *name, int len,
> + const char *cf_name, int cf_len,
> u64 ino, unsigned int d_type)
> {
> struct ovl_cache_entry *p;
>
> p = kmalloc(struct_size(p, name, len + 1), GFP_KERNEL);
> - if (!p)
> + if (!p) {
> + kfree(cf_name);
Not needed.
Caller will get -ENOMEM and will free c_name
No need to repost just for this I can fix on commit.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Thanks,
Amir.
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