Are there anyone who can review this bugfix? Seiji > -----Original Message----- > From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Seiji Aguchi > Sent: Friday, September 27, 2013 4:24 PM > To: linux-kernel@xxxxxxxxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx; tony.luck@xxxxxxxxx; matt.fleming@xxxxxxxxx > Cc: dle-develop@xxxxxxxxxxxxxxxxxxxxx; Tomoki Sekiyama > Subject: [RFC][PATCH v2] efivars,efi-pstore: Hold off deletion of sysfs entry until the scan is completed > > Change form v1 > - Rebase to 3.12-rc2 > > Currently, when mounting pstore file system, a read callback of efi_pstore > driver runs mutiple times as below. > > - In the first read callback, scan efivar_sysfs_list from head and pass > a kmsg buffer of a entry to an upper pstore layer. > - In the second read callback, rescan efivar_sysfs_list from the entry and pass > another kmsg buffer to it. > - Repeat the scan and pass until the end of efivar_sysfs_list. > > In this process, an entry is read across the multiple read function calls. > To avoid race between the read and erasion, the whole process above is > protected by a spinlock, holding in open() and releasing in close(). > > At the same time, kmemdup() is called to pass the buffer to pstore filesystem > during it. > And then, it causes a following lockdep warning. > > To make the read callback runnable without taking spinlok, > holding off a deletion of sysfs entry if it happens while scanning it > via efi_pstore, and deleting it after the scan is completed. > > To implement it, this patch introduces two flags, scanning and deleting, > to efivar_entry. > Also, __efivar_entry_get() is removed because it was used in efi_pstore only. > > [ 1.143710] ------------[ cut here ]------------ > [ 1.144058] WARNING: CPU: 1 PID: 1 at kernel/lockdep.c:2740 > lockdep_trace_alloc+0x104/0x110() > [ 1.144058] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)) > [ 1.144058] Modules linked in: > > [ 1.144058] CPU: 1 PID: 1 Comm: systemd Not tainted 3.11.0-rc5 #2 > [ 1.144058] 0000000000000009 ffff8800797e9ae0 ffffffff816614a5 > ffff8800797e9b28 > [ 1.144058] ffff8800797e9b18 ffffffff8105510d 0000000000000080 > 0000000000000046 > [ 1.144058] 00000000000000d0 00000000000003af ffffffff81ccd0c0 > ffff8800797e9b78 > [ 1.144058] Call Trace: > [ 1.144058] [<ffffffff816614a5>] dump_stack+0x54/0x74 > [ 1.144058] [<ffffffff8105510d>] warn_slowpath_common+0x7d/0xa0 > [ 1.144058] [<ffffffff8105517c>] warn_slowpath_fmt+0x4c/0x50 > [ 1.144058] [<ffffffff8131290f>] ? vsscanf+0x57f/0x7b0 > [ 1.144058] [<ffffffff810bbd74>] lockdep_trace_alloc+0x104/0x110 > [ 1.144058] [<ffffffff81192da0>] __kmalloc_track_caller+0x50/0x280 > [ 1.144058] [<ffffffff815147bb>] ? > efi_pstore_read_func.part.1+0x12b/0x170 > [ 1.144058] [<ffffffff8115b260>] kmemdup+0x20/0x50 > [ 1.144058] [<ffffffff815147bb>] efi_pstore_read_func.part.1+0x12b/0x170 > [ 1.144058] [<ffffffff81514800>] ? > efi_pstore_read_func.part.1+0x170/0x170 > [ 1.144058] [<ffffffff815148b4>] efi_pstore_read_func+0xb4/0xe0 > [ 1.144058] [<ffffffff81512b7b>] __efivar_entry_iter+0xfb/0x120 > [ 1.144058] [<ffffffff8151428f>] efi_pstore_read+0x3f/0x50 > [ 1.144058] [<ffffffff8128d7ba>] pstore_get_records+0x9a/0x150 > [ 1.158207] [<ffffffff812af25c>] ? selinux_d_instantiate+0x1c/0x20 > [ 1.158207] [<ffffffff8128ce30>] ? parse_options+0x80/0x80 > [ 1.158207] [<ffffffff8128ced5>] pstore_fill_super+0xa5/0xc0 > [ 1.158207] [<ffffffff811ae7d2>] mount_single+0xa2/0xd0 > [ 1.158207] [<ffffffff8128ccf8>] pstore_mount+0x18/0x20 > [ 1.158207] [<ffffffff811ae8b9>] mount_fs+0x39/0x1b0 > [ 1.158207] [<ffffffff81160550>] ? __alloc_percpu+0x10/0x20 > [ 1.158207] [<ffffffff811c9493>] vfs_kern_mount+0x63/0xf0 > [ 1.158207] [<ffffffff811cbb0e>] do_mount+0x23e/0xa20 > [ 1.158207] [<ffffffff8115b51b>] ? strndup_user+0x4b/0xf0 > [ 1.158207] [<ffffffff811cc373>] SyS_mount+0x83/0xc0 > [ 1.158207] [<ffffffff81673cc2>] system_call_fastpath+0x16/0x1b > [ 1.158207] ---[ end trace 61981bc62de9f6f4 ]--- > > Signed-off-by: Seiji Aguchi <seiji.aguchi@xxxxxxx> > --- > drivers/firmware/efi/efi-pstore.c | 145 +++++++++++++++++++++++++++++++++++--- > drivers/firmware/efi/efivars.c | 3 +- > drivers/firmware/efi/vars.c | 39 +++------- > include/linux/efi.h | 4 +- > 4 files changed, 151 insertions(+), 40 deletions(-) > > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c > index 5002d50..53001a5 100644 > --- a/drivers/firmware/efi/efi-pstore.c > +++ b/drivers/firmware/efi/efi-pstore.c > @@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644); > > static int efi_pstore_open(struct pstore_info *psi) > { > - efivar_entry_iter_begin(); > psi->data = NULL; > return 0; > } > > static int efi_pstore_close(struct pstore_info *psi) > { > - efivar_entry_iter_end(); > psi->data = NULL; > return 0; > } > @@ -39,6 +37,23 @@ struct pstore_read_data { > char **buf; > }; > > +/** > + * efi_pstore_read_func > + * @entry: reading entry > + * @data: data of the entry > + * > + * This function runs in non-atomic context. > + * > + * Also, it returns a size of NVRAM entry logged via efi_pstore_write(). > + * pstore in accordance with the returned value as below. > + * > + * size > 0: Got data of an entry logged via efi_pstore_write() successfully, > + * and pstore filesystem will continue reading subsequent entries. > + * size == 0: Entry was not logged via efi_pstore_write(), > + * and efi_pstore driver will continue reading subsequent entries. > + * size < 0: Failed to get data of entry logging via efi_pstore_write(), > + * and pstore will stop reading entry. > + */ > static int efi_pstore_read_func(struct efivar_entry *entry, void *data) > { > efi_guid_t vendor = LINUX_EFI_CRASH_GUID; > @@ -88,8 +103,9 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data) > return 0; > > entry->var.DataSize = 1024; > - __efivar_entry_get(entry, &entry->var.Attributes, > - &entry->var.DataSize, entry->var.Data); > + efivar_entry_get(entry, &entry->var.Attributes, > + &entry->var.DataSize, entry->var.Data); > + > size = entry->var.DataSize; > > *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL); > @@ -98,12 +114,114 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data) > return size; > } > > +/** > + * efi_pstore_scan_sysfs_enter > + * @entry: scanning entry > + * @next: next entry > + * @head: list head > + */ > +static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos, > + struct efivar_entry *next, > + struct list_head *head) > +{ > + pos->scanning = true; > + if (&next->list != head) > + next->scanning = true; > + > + /* > + * Release a spin_lock because efi_pstore_read_func() should > + * run in non-atomic context to allocate buffer dynamically. > + */ > + efivar_entry_iter_end(); > +} > + > +/** > + * __efi_pstore_scan_sysfs_exit > + * @entry: deleting entry > + * @turn_off_scanning: Check if a scanning flag should be turned off > + */ > +static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry, > + bool turn_off_scanning) > +{ > + if (entry->deleting) { > + list_del(&entry->list); > + efivar_entry_iter_end(); > + efivar_unregister(entry); > + efivar_entry_iter_begin(); > + } else if (turn_off_scanning) > + entry->scanning = false; > +} > + > +/** > + * efi_pstore_scan_sysfs_exit > + * @pos: scanning entry > + * @next: next entry > + * @head: list head > + * @stop: a flag checking if scanning will stop > + */ > +static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos, > + struct efivar_entry *next, > + struct list_head *head, bool stop) > +{ > + /* Hold a spinlock to access efivar_entry safely. */ > + efivar_entry_iter_begin(); > + __efi_pstore_scan_sysfs_exit(pos, true); > + if (stop) > + __efi_pstore_scan_sysfs_exit(next, &next->list != head); > +} > + > +/** > + * efi_pstore_sysfs_entry_iter > + * > + * @data: function-specific data to pass to callback > + * @pos: entry to begin iterating from > + * > + * You MUST call efivar_enter_iter_begin() before this function, and > + * efivar_entry_iter_end() afterwards. > + * > + * It is possible to begin iteration from an arbitrary entry within > + * the list by passing @pos. @pos is updated on return to point to > + * the next entry of the last one passed to efi_pstore_read_func(). > + * To begin iterating from the beginning of the list @pos must be %NULL. > + */ > +static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos) > +{ > + struct efivar_entry *entry, *n; > + struct list_head *head = &efivar_sysfs_list; > + int size = 0; > + > + if (!*pos) { > + list_for_each_entry_safe(entry, n, head, list) { > + efi_pstore_scan_sysfs_enter(entry, n, head); > + > + size = efi_pstore_read_func(entry, data); > + efi_pstore_scan_sysfs_exit(entry, n, head, size < 0); > + if (size) > + break; > + } > + *pos = n; > + return size; > + } > + > + list_for_each_entry_safe_from((*pos), n, head, list) { > + efi_pstore_scan_sysfs_enter((*pos), n, head); > + > + size = efi_pstore_read_func((*pos), data); > + efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0); > + if (size) > + break; > + } > + *pos = n; > + return size; > +} > + > static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type, > int *count, struct timespec *timespec, > char **buf, bool *compressed, > struct pstore_info *psi) > { > struct pstore_read_data data; > + ssize_t size; > > data.id = id; > data.type = type; > @@ -112,8 +230,11 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type, > data.compressed = compressed; > data.buf = buf; > > - return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data, > - (struct efivar_entry **)&psi->data); > + efivar_entry_iter_begin(); > + size = efi_pstore_sysfs_entry_iter(&data, > + (struct efivar_entry **)&psi->data); > + efivar_entry_iter_end(); > + return size; > } > > static int efi_pstore_write(enum pstore_type_id type, > @@ -184,9 +305,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data) > return 0; > } > > + if (entry->scanning) { > + /* > + * Skip deletion because this entry will be deleted > + * after scanning is completed. > + */ > + entry->deleting = true; > + } else > + list_del(&entry->list); > + > /* found */ > __efivar_entry_delete(entry); > - list_del(&entry->list); > > return 1; > } > @@ -216,7 +345,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count, > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry); > efivar_entry_iter_end(); > > - if (found) > + if (found && !entry->scanning) > efivar_unregister(entry); > > return 0; > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c > index 8a7432a..831bc5c 100644 > --- a/drivers/firmware/efi/efivars.c > +++ b/drivers/firmware/efi/efivars.c > @@ -388,7 +388,8 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj, > if (err) > return err; > > - efivar_unregister(entry); > + if (!entry->scanning) > + efivar_unregister(entry); > > /* It's dead Jim.... */ > return count; > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c > index 391c67b..573ed92 100644 > --- a/drivers/firmware/efi/vars.c > +++ b/drivers/firmware/efi/vars.c > @@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid, > if (!found) > return NULL; > > - if (remove) > - list_del(&entry->list); > + if (remove) { > + if (entry->scanning) { > + /* > + * The entry will be deleted > + * after scanning is completed. > + */ > + entry->deleting = true; > + } else > + list_del(&entry->list); > + } > > return entry; > } > @@ -715,33 +723,6 @@ int efivar_entry_size(struct efivar_entry *entry, unsigned long *size) > EXPORT_SYMBOL_GPL(efivar_entry_size); > > /** > - * __efivar_entry_get - call get_variable() > - * @entry: read data for this variable > - * @attributes: variable attributes > - * @size: size of @data buffer > - * @data: buffer to store variable data > - * > - * The caller MUST call efivar_entry_iter_begin() and > - * efivar_entry_iter_end() before and after the invocation of this > - * function, respectively. > - */ > -int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes, > - unsigned long *size, void *data) > -{ > - const struct efivar_operations *ops = __efivars->ops; > - efi_status_t status; > - > - WARN_ON(!spin_is_locked(&__efivars->lock)); > - > - status = ops->get_variable(entry->var.VariableName, > - &entry->var.VendorGuid, > - attributes, size, data); > - > - return efi_status_to_err(status); > -} > -EXPORT_SYMBOL_GPL(__efivar_entry_get); > - > -/** > * efivar_entry_get - call get_variable() > * @entry: read data for this variable > * @attributes: variable attributes > diff --git a/include/linux/efi.h b/include/linux/efi.h > index 5f8f176..1e3388e 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -782,6 +782,8 @@ struct efivar_entry { > struct efi_variable var; > struct list_head list; > struct kobject kobj; > + bool scanning; > + bool deleting; > }; > > extern struct list_head efivar_sysfs_list; > @@ -809,8 +811,6 @@ int __efivar_entry_delete(struct efivar_entry *entry); > int efivar_entry_delete(struct efivar_entry *entry); > > int efivar_entry_size(struct efivar_entry *entry, unsigned long *size); > -int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes, > - unsigned long *size, void *data); > int efivar_entry_get(struct efivar_entry *entry, u32 *attributes, > unsigned long *size, void *data); > int efivar_entry_set(struct efivar_entry *entry, u32 attributes, > -- > 1.8.2.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ ��.n��������+%������w��{.n�����{����* jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
