Hi Madper, Thank you for assisting me. But, I need to discuss the implementation with Matt more. After the discussion, I will post v4 and ask you to test it. Please wait for a while. Seiji > -----Original Message----- > From: Madper Xie [mailto:cxie@xxxxxxxxxx] > Sent: Thursday, October 17, 2013 11:07 AM > To: Madper Xie > Cc: Seiji Aguchi; linux-kernel@xxxxxxxxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx; matt.fleming@xxxxxxxxx; tony.luck@xxxxxxxxx; Tomoki > Sekiyama; dle-develop@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed > > Hi folks, > I tested it on my DELL XPS desktop. And it won't show any warnings > when I mounting pstore and deleting pstore items after this patch > applied. > > Tested-by: Madper Xie > cxie@xxxxxxxxxx writes: > > > Oops, It seems my mu4e(a email client for emacs)'s auto-indent breaks the > > patch... I apologize for this... > > > > seiji.aguchi@xxxxxxx writes: > > > >> Hi Madper, > >> > >> I tested this patch on 3.12-rc4. > >> Could you please send me the log when you failed to apply? > >> > >> Seiji > >> > >>> -----Original Message----- > >>> From: Madper Xie [mailto:cxie@xxxxxxxxxx] > >>> Sent: Thursday, October 17, 2013 1:54 AM > >>> To: Seiji Aguchi > >>> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx; matt.fleming@xxxxxxxxx; tony.luck@xxxxxxxxx; Tomoki Sekiyama; > dle- > >>> develop@xxxxxxxxxxxxxxxxxxxxx > >>> Subject: Re: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed > >>> > >>> Howdy Seiji, > >>> I failed appily this patch to both 3.12-rc2 and 3.12-rc4. Could you > >>> please let me know which is the right tree for this patch? > >>> > >>> Thanks, > >>> Madper. > >>> seiji.aguchi@xxxxxxx writes: > >>> > >>> > Change from v2: > >>> > - Move dynamic memory allocation to efi_pstore_read() before holding > >>> > efivars->lock to protect entry->var.Data. > >>> > - Access to entry->scanning while holding efivars->lock. > >>> > - Move a comment about a returned value from efi_pstore_read_func() to > >>> > efi_pstore_read() because "size < 0" case may happen in efi_pstore_read(). > >>> > > >>> > 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 dynamic memory allocation runnable without taking spinlock, > >>> > 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. > >>> > > >>> > [ 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 | 143 +++++++++++++++++++++++++++++++++++--- > >>> > drivers/firmware/efi/efivars.c | 12 ++-- > >>> > drivers/firmware/efi/vars.c | 12 +++- > >>> > include/linux/efi.h | 2 + > >>> > 4 files changed, 153 insertions(+), 16 deletions(-) > >>> > > >>> > diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c > >>> > index 5002d50..ebd5dbc 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; > >>> > } > >>> > @@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data) > >>> > __efivar_entry_get(entry, &entry->var.Attributes, > >>> > &entry->var.DataSize, entry->var.Data); > >>> > size = entry->var.DataSize; > >>> > + memcpy(*cb_data->buf, entry->var.Data, (size_t)min_t(unsigned long, > >>> > + 1024, size)); > >>> > > >>> > - *cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL); > >>> > - if (*cb_data->buf == NULL) > >>> > - return -ENOMEM; > >>> > 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; > >>> > +} > >>> > + > >>> > +/** > >>> > + * __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) > >>> > +{ > >>> > + __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; > >>> > +} > >>> > + > >>> > +/** > >>> > + * efi_pstore_read > >>> > + * > >>> > + * This function returns a size of NVRAM entry logged via efi_pstore_write(). > >>> > + * The meaning and behavior of efi_pstore/pstore are 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 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 +216,17 @@ 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); > >>> > + *data.buf = kzalloc(1024, GFP_KERNEL); > >>> > + if (!*data.buf) > >>> > + return -ENOMEM; > >>> > + > >>> > + efivar_entry_iter_begin(); > >>> > + size = efi_pstore_sysfs_entry_iter(&data, > >>> > + (struct efivar_entry **)&psi->data); > >>> > + efivar_entry_iter_end(); > >>> > + if (size <= 0) > >>> > + kfree(*data.buf); > >>> > + return size; > >>> > } > >>> > > >>> > static int efi_pstore_write(enum pstore_type_id type, > >>> > @@ -184,9 +297,17 @@ 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; > >>> > } > >>> > @@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count, > >>> > > >>> > efivar_entry_iter_begin(); > >>> > found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry); > >>> > - efivar_entry_iter_end(); > >>> > > >>> > - if (found) > >>> > + if (found && !entry->scanning) { > >>> > + efivar_entry_iter_end(); > >>> > efivar_unregister(entry); > >>> > + } else > >>> > + efivar_entry_iter_end(); > >>> > > >>> > return 0; > >>> > } > >>> > diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c > >>> > index 8a7432a..8c5a61a 100644 > >>> > --- a/drivers/firmware/efi/efivars.c > >>> > +++ b/drivers/firmware/efi/efivars.c > >>> > @@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj, > >>> > else if (__efivar_entry_delete(entry)) > >>> > err = -EIO; > >>> > > >>> > - efivar_entry_iter_end(); > >>> > - > >>> > - if (err) > >>> > + if (err) { > >>> > + efivar_entry_iter_end(); > >>> > return err; > >>> > + } > >>> > > >>> > - efivar_unregister(entry); > >>> > + if (!entry->scanning) { > >>> > + efivar_entry_iter_end(); > >>> > + efivar_unregister(entry); > >>> > + } else > >>> > + efivar_entry_iter_end(); > >>> > > >>> > /* It's dead Jim.... */ > >>> > return count; > >>> > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c > >>> > index 391c67b..b22659c 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; > >>> > } > >>> > diff --git a/include/linux/efi.h b/include/linux/efi.h > >>> > index 5f8f176..04088fb 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; > >>> > >>> > >>> -- > >>> Best, > >>> Madper Xie. > > > -- > Best, > Madper Xie. -- To unsubscribe from this list: send the line "unsubscribe 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