Em 17/08/2025 11:33, Amir Goldstein escreveu:
On Thu, Aug 14, 2025 at 7:22 PM André Almeida <andrealmeid@xxxxxxxxxx> 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@xxxxxxxxxx>
---
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.
