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Protect candidate file copy under stamp_lock during multithread scan

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This commit is contained in:
Andrea Mazzoleni 2026-07-06 16:19:21 +02:00
parent 562d59d9c8
commit 952ea337e7
1 changed files with 20 additions and 13 deletions
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33
cmdline/scan.c
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@ -785,8 +785,15 @@ static void scan_file(struct snapraid_scan* scan, int is_diff, const char* sub,
/* remove from the name set */
tommy_hashdyn_remove_existing(&disk->pathset, &file->pathset);
/* save the new name */
/*
* Protect the file->sub mutation because other threads may concurrently
* search the stampset and read this file's name string inside
* file_namestamp_compare/file_pathstamp_compare, or when doing
* a pathcpy() during copy detection.
*/
stamp_lock(disk);
file_rename(file, sub);
stamp_unlock(disk);
/* reinsert in the name set */
tommy_hashdyn_insert(&disk->pathset, &file->pathset, file, file_path_hash(file->sub));
@ -1040,6 +1047,8 @@ static void scan_file(struct snapraid_scan* scan, int is_diff, const char* sub,
struct snapraid_disk* other_disk = i->data;
struct snapraid_file* other_file;
char sub_other[PATH_MAX];
stamp_lock(other_disk);
/* if the nanosecond part of the time stamp is valid, search */
/* for name and stamp, otherwise for path and stamp */
@ -1047,6 +1056,11 @@ static void scan_file(struct snapraid_scan* scan, int is_diff, const char* sub,
other_file = tommy_hashdyn_search(&other_disk->stampset, file_namestamp_compare, file, hash);
else
other_file = tommy_hashdyn_search(&other_disk->stampset, file_pathstamp_compare, file, hash);
if (other_file) {
/* copy sub path safely before unlocking stamp_lock */
pathcpy(sub_other, sizeof(sub_other), other_file->sub);
}
stamp_unlock(other_disk);
/* if found, and it's a fully hashed file */
@ -1054,13 +1068,6 @@ static void scan_file(struct snapraid_scan* scan, int is_diff, const char* sub,
char path_other[PATH_MAX];
struct stat other_st;
/*
* Protect the write as multiple threads may write the same FILE_IS_RELOCATED bit.
*
* Note that this flag is written in the "shared" portion of the flags,
* intended exactly to avoid data race from multiple threads using
* the stamp_lock() protection.
*/
stamp_lock(other_disk);
file_flag_set(other_file, FILE_IS_RELOCATED);
stamp_unlock(other_disk);
@ -1069,20 +1076,20 @@ static void scan_file(struct snapraid_scan* scan, int is_diff, const char* sub,
file_copy(other_file, file);
/* check if other file still exists */
pathprint(path_other, sizeof(path_other), "%s%s", other_disk->dir, other_file->sub);
pathprint(path_other, sizeof(path_other), "%s%s", other_disk->dir, sub_other);
if (lstat(path_other, &other_st) == 0) {
++scan->count_copy;
log_tag("scan:copy:%s:%s:%s:%s\n", other_disk->name, esc_tag(other_file->sub), disk->name, esc_tag(file->sub));
log_tag("scan:copy:%s:%s:%s:%s\n", other_disk->name, esc_tag(sub_other), disk->name, esc_tag(file->sub));
if (is_diff) {
msg_info("copy %s -> %s\n", fmt_term(other_disk, other_file->sub), fmt_term(disk, file->sub));
msg_info("copy %s -> %s\n", fmt_term(other_disk, sub_other), fmt_term(disk, file->sub));
}
} else {
++scan->count_relocate;
log_tag("scan:relocate:%s:%s:%s:%s\n", other_disk->name, esc_tag(other_file->sub), disk->name, esc_tag(file->sub));
log_tag("scan:relocate:%s:%s:%s:%s\n", other_disk->name, esc_tag(sub_other), disk->name, esc_tag(file->sub));
if (is_diff) {
msg_info("relocate %s -> %s\n", fmt_term(other_disk, other_file->sub), fmt_term(disk, file->sub));
msg_info("relocate %s -> %s\n", fmt_term(other_disk, sub_other), fmt_term(disk, file->sub));
}
}