On Tue, Apr 14 2026, Pasha Tatashin wrote: > To remove the fixed limit on the number of preserved files per session, > transition the file metadata serialization from a single contiguous memory > block to a chain of linked blocks.
Same comment as previous patch about a general linked block data structure here. > > ABI Changes: > - Define 'struct luo_file_header_ser' to manage linked blocks in preserved > memory. > - Update 'struct luo_file_set_ser' to point to the head of the block chain. > - Bump the session ABI version to 'luo-session-v4' to reflect these breaking > changes. > > Signed-off-by: Pasha Tatashin <[email protected]> > --- > include/linux/kho/abi/luo.h | 35 ++++- > kernel/liveupdate/luo_file.c | 226 ++++++++++++++++++++----------- > kernel/liveupdate/luo_internal.h | 17 ++- > 3 files changed, 189 insertions(+), 89 deletions(-) > > diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h > index f5732958545e..a15f6a0f3d93 100644 > --- a/include/linux/kho/abi/luo.h > +++ b/include/linux/kho/abi/luo.h > @@ -84,8 +84,13 @@ > * > * - struct luo_session_ser: > * Metadata for a single session, including its name and a physical > pointer > - * to another preserved memory block containing an array of > - * `struct luo_file_ser` for all files in that session. > + * to the first `struct luo_file_header_ser` for all files in that > session. > + * Multiple blocks are linked via the `next` field in the header. > + * > + * - struct luo_file_header_ser: > + * Header for the file data block. Contains the physical address of the > + * next file data block and the number of `struct luo_file_ser` entries > + * that follow this header in the current block. > * > * - struct luo_file_ser: > * Metadata for a single preserved file. Contains the `compatible` > string to > @@ -134,11 +139,29 @@ struct luo_file_ser { > u64 token; > } __packed; > > +/** > + * struct luo_file_header_ser - Header for the serialized file data block. > + * @next: Physical address of the next struct luo_file_header_ser. > + * @count: The number of `struct luo_file_ser` entries that immediately > + * follow this header in the memory block. > + * > + * This structure is located at the beginning of a block of > + * physical memory preserved across the kexec. It provides the necessary > + * metadata to interpret the array of file entries that follow. > + * > + * If this structure is modified, `LUO_FDT_SESSION_COMPATIBLE` must be > updated. > + */ > +struct luo_file_header_ser { Nit: Same as before, can we rename it to make it clear that this is a block header? > + u64 next; > + u64 count; > +} __packed; > + > /** > * struct luo_file_set_ser - Represents the serialized metadata for file set > - * @files: The physical address of a contiguous memory block that holds > - * the serialized state of files (array of luo_file_ser) in this > file > - * set. > + * @files: The physical address of the first `struct luo_file_header_ser`. > + * This structure is the header for a block of memory containing > + * an array of `struct luo_file_ser` entries. Multiple blocks are > + * linked via the `next` field in the header. > * @count: The total number of files that were part of this session during > * serialization. Used for iteration and validation during > * restoration. > @@ -154,7 +177,7 @@ struct luo_file_set_ser { > * luo_session_header_ser > */ > #define LUO_FDT_SESSION_NODE_NAME "luo-session" > -#define LUO_FDT_SESSION_COMPATIBLE "luo-session-v3" > +#define LUO_FDT_SESSION_COMPATIBLE "luo-session-v4" > #define LUO_FDT_SESSION_HEADER "luo-session-header" > > /** > diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c > index dedbb8d02e6a..20a2d776cff4 100644 > --- a/kernel/liveupdate/luo_file.c > +++ b/kernel/liveupdate/luo_file.c > @@ -119,10 +119,12 @@ static LIST_HEAD(luo_file_handler_list); > /* Keep track of files being preserved by LUO */ > static DEFINE_XARRAY(luo_preserved_files); > > -/* 2 4K pages, give space for 128 files per file_set */ > +/* 2 4K pages, give space for 127 files per block */ > #define LUO_FILE_PGCNT 2ul > -#define LUO_FILE_MAX \ > - ((LUO_FILE_PGCNT << PAGE_SHIFT) / sizeof(struct luo_file_ser)) > +#define LUO_FILE_BLOCK_MAX \ > + (((LUO_FILE_PGCNT << PAGE_SHIFT) - \ > + sizeof(struct luo_file_header_ser)) / \ > + sizeof(struct luo_file_ser)) > > /** > * struct luo_file - Represents a single preserved file instance. > @@ -158,7 +160,7 @@ static DEFINE_XARRAY(luo_preserved_files); > * and the serialized state handle returned by the handler's .preserve() > * operation. > * > - * These instances are tracked in a per-file_set list. The @serialized_data > + * These structures are tracked in a per-file_set list. The @serialized_data > * field, which holds a handle to the file's serialized state, may be updated > * during the .freeze() callback before being serialized for the next kernel. > * After reboot, these structures are recreated by luo_file_deserialize() and > @@ -175,37 +177,68 @@ struct luo_file { > u64 token; > }; > > -static int luo_alloc_files_mem(struct luo_file_set *file_set) > +static int luo_file_add_block(struct luo_file_set *file_set, > + struct luo_file_header_ser *ser) > { > - size_t size; > - void *mem; > + struct luo_file_block *block; > > - if (file_set->files) > - return 0; > - > - WARN_ON_ONCE(file_set->count); > + if (file_set->nblocks >= LUO_MAX_BLOCKS) > + return -ENOSPC; > > - size = LUO_FILE_PGCNT << PAGE_SHIFT; > - mem = kho_alloc_preserve(size); > - if (IS_ERR(mem)) > - return PTR_ERR(mem); > + block = kzalloc_obj(*block); > + if (!block) > + return -ENOMEM; > > - file_set->files = mem; > + block->ser = ser; > + list_add_tail(&block->list, &file_set->blocks); > + file_set->nblocks++; > > return 0; > } > > -static void luo_free_files_mem(struct luo_file_set *file_set) > +static int luo_file_create_ser_block(struct luo_file_set *file_set) > { > - /* If file_set has files, no need to free preservation memory */ > - if (file_set->count) > - return; > + struct luo_file_block *last = NULL; > + struct luo_file_header_ser *ser; > + int err; > > - if (!file_set->files) > - return; > + ser = kho_alloc_preserve(LUO_FILE_PGCNT << PAGE_SHIFT); > + if (IS_ERR(ser)) > + return PTR_ERR(ser); > + > + if (!list_empty(&file_set->blocks)) > + last = list_last_entry(&file_set->blocks, struct > luo_file_block, list); > + > + err = luo_file_add_block(file_set, ser); > + if (err) > + goto err_unpreserve; > + > + if (last) > + last->ser->next = virt_to_phys(ser); Same comments as last patch about list_last_entry_or_null() and moving this to luo_file_add_block(). > + > + return 0; > > - kho_unpreserve_free(file_set->files); > - file_set->files = NULL; > +err_unpreserve: > + kho_unpreserve_free(ser); > + return err; > +} > + > +static void luo_file_destroy_ser_blocks(struct luo_file_set *file_set, > + bool unpreserve) > +{ > + struct luo_file_block *block, *tmp; > + > + list_for_each_entry_safe(block, tmp, &file_set->blocks, list) { > + if (block->ser) { Same here. block is always created with its ser, so why have this check? > + if (unpreserve) > + kho_unpreserve_free(block->ser); > + else > + kho_restore_free(block->ser); And same comment about the nastiness here, but once again I have nothing better to offer. > + } > + list_del(&block->list); > + kfree(block); > + file_set->nblocks--; > + } > } > > static unsigned long luo_get_id(struct liveupdate_file_handler *fh, > @@ -247,7 +280,9 @@ static bool luo_token_is_used(struct luo_file_set > *file_set, u64 token) > * 3. Iterates through registered handlers, calling can_preserve() to find > one > * compatible with the given @fd. > * 4. Calls the handler's .preserve() operation, which saves the file's state > - * and returns an opaque private data handle. > + * and returns an opaque u64 handle. This is typically performed while the > + * workload is still active to minimize the downtime during the > + * actual reboot transition. > * 5. Adds the new instance to the file_set's internal list. > * > * On success, LUO takes a reference to the 'struct file' and considers it > @@ -277,17 +312,16 @@ int luo_preserve_file(struct luo_file_set *file_set, > u64 token, int fd) > if (luo_token_is_used(file_set, token)) > return -EEXIST; > > - if (file_set->count == LUO_FILE_MAX) > - return -ENOSPC; > + if (file_set->count == file_set->nblocks * LUO_FILE_BLOCK_MAX) { > + err = luo_file_create_ser_block(file_set); > + if (err) > + return err; > + } > > file = fget(fd); > if (!file) > return -EBADF; > > - err = luo_alloc_files_mem(file_set); > - if (err) > - goto err_fput; > - > err = -ENOENT; > down_read(&luo_register_rwlock); > list_private_for_each_entry(fh, &luo_file_handler_list, list) { > @@ -301,7 +335,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 > token, int fd) > > /* err is still -ENOENT if no handler was found */ > if (err) > - goto err_free_files_mem; > + goto err_fput; > > /* safe to use fh because its module is pinned */ > err = xa_insert(&luo_preserved_files, luo_get_id(fh, file), > @@ -345,8 +379,6 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 > token, int fd) > xa_erase(&luo_preserved_files, luo_get_id(fh, file)); > err_module_put: > module_put(fh->ops->owner); > -err_free_files_mem: > - luo_free_files_mem(file_set); > err_fput: > fput(file); > > @@ -399,7 +431,7 @@ void luo_file_unpreserve_files(struct luo_file_set > *file_set) > kfree(luo_file); > } > > - luo_free_files_mem(file_set); > + luo_file_destroy_ser_blocks(file_set, true); > } > > static int luo_file_freeze_one(struct luo_file_set *file_set, > @@ -446,6 +478,7 @@ static void __luo_file_unfreeze(struct luo_file_set > *file_set, > struct luo_file *failed_entry) > { > struct list_head *files_list = &file_set->files_list; > + struct luo_file_block *block; > struct luo_file *luo_file; > > list_for_each_entry(luo_file, files_list, list) { > @@ -455,7 +488,11 @@ static void __luo_file_unfreeze(struct luo_file_set > *file_set, > luo_file_unfreeze_one(file_set, luo_file); > } > > - memset(file_set->files, 0, LUO_FILE_PGCNT << PAGE_SHIFT); > + list_for_each_entry(block, &file_set->blocks, list) { > + block->ser->count = 0; > + memset(block->ser + 1, 0, > + (LUO_FILE_PGCNT << PAGE_SHIFT) - sizeof(*block->ser)); > + } > } > > /** > @@ -494,7 +531,8 @@ static void __luo_file_unfreeze(struct luo_file_set > *file_set, > int luo_file_freeze(struct luo_file_set *file_set, > struct luo_file_set_ser *file_set_ser) > { > - struct luo_file_ser *file_ser = file_set->files; > + struct luo_file_block *block; > + struct luo_file_ser *file_ser; > struct luo_file *luo_file; > int err; > int i; > @@ -502,11 +540,18 @@ int luo_file_freeze(struct luo_file_set *file_set, > if (!file_set->count) > return 0; > > - if (WARN_ON(!file_ser)) > - return -EINVAL; > + block = list_first_entry(&file_set->blocks, struct luo_file_block, > list); > + file_ser = (void *)(block->ser + 1); > > i = 0; > list_for_each_entry(luo_file, &file_set->files_list, list) { > + if (i == LUO_FILE_BLOCK_MAX) { > + block->ser->count = i; > + block = list_next_entry(block, list); > + file_ser = (void *)(block->ser + 1); > + i = 0; > + } > + > err = luo_file_freeze_one(file_set, luo_file); > if (err < 0) { > pr_warn("Freeze failed for token[%#0llx] handler[%s] > err[%pe]\n", > @@ -521,10 +566,13 @@ int luo_file_freeze(struct luo_file_set *file_set, > file_ser[i].token = luo_file->token; > i++; > } > + block->ser->count = i; > > file_set_ser->count = file_set->count; > - if (file_set->files) > - file_set_ser->files = virt_to_phys(file_set->files); > + if (!list_empty(&file_set->blocks)) { > + block = list_first_entry(&file_set->blocks, struct > luo_file_block, list); > + file_set_ser->files = virt_to_phys(block->ser); > + } > > return 0; > > @@ -746,10 +794,7 @@ int luo_file_finish(struct luo_file_set *file_set) > kfree(luo_file); > } > > - if (file_set->files) { > - kho_restore_free(file_set->files); > - file_set->files = NULL; > - } > + luo_file_destroy_ser_blocks(file_set, false); > > return 0; > } > @@ -782,8 +827,10 @@ int luo_file_finish(struct luo_file_set *file_set) > int luo_file_deserialize(struct luo_file_set *file_set, > struct luo_file_set_ser *file_set_ser) > { > - struct luo_file_ser *file_ser; > - u64 i; > + struct luo_file_header_ser *header_ser; > + struct luo_file_block *block; > + u64 header_ser_pa; > + int err; > > if (!file_set_ser->files) { > WARN_ON(file_set_ser->count); > @@ -791,7 +838,15 @@ int luo_file_deserialize(struct luo_file_set *file_set, > } > > file_set->count = file_set_ser->count; > - file_set->files = phys_to_virt(file_set_ser->files); > + header_ser_pa = file_set_ser->files; > + > + while (header_ser_pa) { > + header_ser = phys_to_virt(header_ser_pa); > + err = luo_file_add_block(file_set, header_ser); > + if (err) > + return err; > + header_ser_pa = header_ser->next; > + } > > /* > * Note on error handling: > @@ -808,42 +863,51 @@ int luo_file_deserialize(struct luo_file_set *file_set, > * userspace to detect the failure and trigger a reboot, which will > * reliably reset devices and reclaim memory. > */ > - file_ser = file_set->files; > - for (i = 0; i < file_set->count; i++) { > - struct liveupdate_file_handler *fh; > - bool handler_found = false; > - struct luo_file *luo_file; > - > - down_read(&luo_register_rwlock); > - list_private_for_each_entry(fh, &luo_file_handler_list, list) { > - if (!strcmp(fh->compatible, file_ser[i].compatible)) { > - if (try_module_get(fh->ops->owner)) > - handler_found = true; > - break; > - } > - } > - up_read(&luo_register_rwlock); > + list_for_each_entry(block, &file_set->blocks, list) { > + struct luo_file_ser *file_ser = (void *)(block->ser + 1); > > - if (!handler_found) { > - pr_warn("No registered handler for compatible '%.*s'\n", > - (int)sizeof(file_ser[i].compatible), > - file_ser[i].compatible); > - return -ENOENT; > + if (block->ser->count > LUO_FILE_BLOCK_MAX) { > + pr_warn("File block contains too many entries: %llu\n", > + block->ser->count); > + return -EINVAL; > } > > - luo_file = kzalloc_obj(*luo_file); > - if (!luo_file) { > - module_put(fh->ops->owner); > - return -ENOMEM; > - } > + for (int i = 0; i < block->ser->count; i++) { > + struct liveupdate_file_handler *fh; > + bool handler_found = false; > + struct luo_file *luo_file; > + > + down_read(&luo_register_rwlock); > + list_private_for_each_entry(fh, &luo_file_handler_list, > list) { > + if (!strcmp(fh->compatible, > file_ser[i].compatible)) { > + if (try_module_get(fh->ops->owner)) > + handler_found = true; > + break; > + } > + } > + up_read(&luo_register_rwlock); > > - /* safe to use fh because its module is pinned */ > - luo_file->fh = fh; > - luo_file->file = NULL; > - luo_file->serialized_data = file_ser[i].data; > - luo_file->token = file_ser[i].token; > - mutex_init(&luo_file->mutex); > - list_add_tail(&luo_file->list, &file_set->files_list); > + if (!handler_found) { > + pr_warn("No registered handler for compatible > '%.*s'\n", > + (int)sizeof(file_ser[i].compatible), > + file_ser[i].compatible); > + return -ENOENT; > + } > + > + luo_file = kzalloc_obj(*luo_file); > + if (!luo_file) { > + module_put(fh->ops->owner); > + return -ENOMEM; > + } > + > + /* safe to use fh because its module is pinned */ > + luo_file->fh = fh; > + luo_file->file = NULL; > + luo_file->serialized_data = file_ser[i].data; > + luo_file->token = file_ser[i].token; > + mutex_init(&luo_file->mutex); > + list_add_tail(&luo_file->list, &file_set->files_list); > + } Nit: this diff is very hard to read. Perhaps splitting this into helper functions would help? > } > > return 0; > @@ -852,12 +916,14 @@ int luo_file_deserialize(struct luo_file_set *file_set, > void luo_file_set_init(struct luo_file_set *file_set) > { > INIT_LIST_HEAD(&file_set->files_list); > + INIT_LIST_HEAD(&file_set->blocks); > } > > void luo_file_set_destroy(struct luo_file_set *file_set) > { > WARN_ON(file_set->count); > WARN_ON(!list_empty(&file_set->files_list)); > + WARN_ON(!list_empty(&file_set->blocks)); > } > > /** > diff --git a/kernel/liveupdate/luo_internal.h > b/kernel/liveupdate/luo_internal.h > index a73f42069301..a92aaa9c073d 100644 > --- a/kernel/liveupdate/luo_internal.h > +++ b/kernel/liveupdate/luo_internal.h > @@ -50,19 +50,30 @@ static inline int luo_ucmd_respond(struct luo_ucmd *ucmd, > */ > #define luo_restore_fail(__fmt, ...) panic(__fmt, ##__VA_ARGS__) > > +/** > + * struct luo_file_block - Internal representation of a file serialization > block. > + * @list: List head for linking blocks in memory. > + * @ser: Pointer to the serialized header in preserved memory. > + */ > +struct luo_file_block { > + struct list_head list; > + struct luo_file_header_ser *ser; > +}; > + > /** > * struct luo_file_set - A set of files that belong to the same sessions. > * @files_list: An ordered list of files associated with this session, it is > * ordered by preservation time. > - * @files: The physically contiguous memory block that holds the > serialized > - * state of files. > + * @blocks: The list of serialization blocks (struct luo_file_block). > * @count: A counter tracking the number of files currently stored in > the > * @files_list for this session. > + * @nblocks: The number of allocated serialization blocks. > */ > struct luo_file_set { > struct list_head files_list; > - struct luo_file_ser *files; > + struct list_head blocks; > long count; > + long nblocks; > }; > > /** -- Regards, Pratyush Yadav
