mirror of https://gitee.com/openkylin/linux.git
efivars, efi-pstore: Hold off deletion of sysfs entry until the scan is completed
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. On the code basis, it seems that all the scanning and deleting logic is not needed because __efivars->lock are not dropped when reading from the EFI variable store. But, the scanning and deleting logic is still needed because an efi-pstore and a pstore filesystem works as follows. In case an entry(A) is found, the pointer is saved to psi->data. And efi_pstore_read() passes the entry(A) to a pstore filesystem by releasing __efivars->lock. And then, the pstore filesystem calls efi_pstore_read() again and the same entry(A), which is saved to psi->data, is used for resuming to scan a sysfs-list. So, to protect the entry(A), the logic is needed. [ 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@hds.com> Tested-by: Madper Xie <cxie@redhat.com> Cc: stable@kernel.org Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Seiji Aguchi
Matt Fleming
parent
6ce4eac1f6
commit
e0d59733f6
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@ -18,14 +18,12 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
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static int efi_pstore_open(struct pstore_info *psi)
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{
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efivar_entry_iter_begin();
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psi->data = NULL;
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return 0;
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}
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static int efi_pstore_close(struct pstore_info *psi)
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{
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efivar_entry_iter_end();
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psi->data = NULL;
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return 0;
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}
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@ -91,19 +89,125 @@ static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
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__efivar_entry_get(entry, &entry->var.Attributes,
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&entry->var.DataSize, entry->var.Data);
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size = entry->var.DataSize;
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memcpy(*cb_data->buf, entry->var.Data,
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(size_t)min_t(unsigned long, EFIVARS_DATA_SIZE_MAX, size));
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*cb_data->buf = kmemdup(entry->var.Data, size, GFP_KERNEL);
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if (*cb_data->buf == NULL)
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return -ENOMEM;
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return size;
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}
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/**
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* efi_pstore_scan_sysfs_enter
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* @entry: scanning entry
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* @next: next entry
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* @head: list head
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*/
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static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
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struct efivar_entry *next,
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struct list_head *head)
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{
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pos->scanning = true;
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if (&next->list != head)
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next->scanning = true;
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}
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/**
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* __efi_pstore_scan_sysfs_exit
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* @entry: deleting entry
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* @turn_off_scanning: Check if a scanning flag should be turned off
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*/
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static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
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bool turn_off_scanning)
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{
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if (entry->deleting) {
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list_del(&entry->list);
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efivar_entry_iter_end();
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efivar_unregister(entry);
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efivar_entry_iter_begin();
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} else if (turn_off_scanning)
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entry->scanning = false;
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}
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/**
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* efi_pstore_scan_sysfs_exit
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* @pos: scanning entry
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* @next: next entry
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* @head: list head
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* @stop: a flag checking if scanning will stop
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*/
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static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
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struct efivar_entry *next,
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struct list_head *head, bool stop)
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{
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__efi_pstore_scan_sysfs_exit(pos, true);
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if (stop)
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__efi_pstore_scan_sysfs_exit(next, &next->list != head);
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}
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/**
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* efi_pstore_sysfs_entry_iter
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*
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* @data: function-specific data to pass to callback
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* @pos: entry to begin iterating from
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*
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* You MUST call efivar_enter_iter_begin() before this function, and
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* efivar_entry_iter_end() afterwards.
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*
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* It is possible to begin iteration from an arbitrary entry within
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* the list by passing @pos. @pos is updated on return to point to
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* the next entry of the last one passed to efi_pstore_read_func().
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* To begin iterating from the beginning of the list @pos must be %NULL.
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*/
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static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
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{
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struct efivar_entry *entry, *n;
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struct list_head *head = &efivar_sysfs_list;
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int size = 0;
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if (!*pos) {
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list_for_each_entry_safe(entry, n, head, list) {
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efi_pstore_scan_sysfs_enter(entry, n, head);
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size = efi_pstore_read_func(entry, data);
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efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
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if (size)
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break;
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}
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*pos = n;
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return size;
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}
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list_for_each_entry_safe_from((*pos), n, head, list) {
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efi_pstore_scan_sysfs_enter((*pos), n, head);
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size = efi_pstore_read_func((*pos), data);
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efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
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if (size)
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break;
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}
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*pos = n;
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return size;
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}
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/**
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* efi_pstore_read
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*
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* This function returns a size of NVRAM entry logged via efi_pstore_write().
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* The meaning and behavior of efi_pstore/pstore are as below.
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*
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* size > 0: Got data of an entry logged via efi_pstore_write() successfully,
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* and pstore filesystem will continue reading subsequent entries.
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* size == 0: Entry was not logged via efi_pstore_write(),
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* and efi_pstore driver will continue reading subsequent entries.
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* size < 0: Failed to get data of entry logging via efi_pstore_write(),
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* and pstore will stop reading entry.
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*/
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static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
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int *count, struct timespec *timespec,
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char **buf, bool *compressed,
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struct pstore_info *psi)
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{
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struct pstore_read_data data;
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ssize_t size;
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data.id = id;
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data.type = type;
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@ -112,8 +216,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
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data.compressed = compressed;
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data.buf = buf;
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return __efivar_entry_iter(efi_pstore_read_func, &efivar_sysfs_list, &data,
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*data.buf = kzalloc(EFIVARS_DATA_SIZE_MAX, GFP_KERNEL);
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if (!*data.buf)
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return -ENOMEM;
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efivar_entry_iter_begin();
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size = efi_pstore_sysfs_entry_iter(&data,
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(struct efivar_entry **)&psi->data);
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efivar_entry_iter_end();
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if (size <= 0)
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kfree(*data.buf);
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return size;
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}
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static int efi_pstore_write(enum pstore_type_id type,
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@ -184,9 +297,17 @@ static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
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return 0;
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}
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if (entry->scanning) {
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/*
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* Skip deletion because this entry will be deleted
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* after scanning is completed.
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*/
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entry->deleting = true;
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} else
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list_del(&entry->list);
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/* found */
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__efivar_entry_delete(entry);
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list_del(&entry->list);
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return 1;
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}
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@ -214,10 +335,12 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
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efivar_entry_iter_begin();
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found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
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efivar_entry_iter_end();
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if (found)
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if (found && !entry->scanning) {
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efivar_entry_iter_end();
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efivar_unregister(entry);
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} else
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efivar_entry_iter_end();
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return 0;
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}
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@ -383,12 +383,16 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
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else if (__efivar_entry_delete(entry))
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err = -EIO;
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if (err) {
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efivar_entry_iter_end();
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if (err)
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return err;
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}
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if (!entry->scanning) {
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efivar_entry_iter_end();
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efivar_unregister(entry);
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} else
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efivar_entry_iter_end();
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/* It's dead Jim.... */
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return count;
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@ -683,8 +683,16 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
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if (!found)
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return NULL;
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if (remove)
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if (remove) {
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if (entry->scanning) {
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/*
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* The entry will be deleted
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* after scanning is completed.
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*/
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entry->deleting = true;
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} else
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list_del(&entry->list);
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}
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return entry;
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}
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@ -801,6 +801,8 @@ struct efivar_entry {
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struct efi_variable var;
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struct list_head list;
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struct kobject kobj;
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bool scanning;
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bool deleting;
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};
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@ -866,6 +868,8 @@ void efivar_run_worker(void);
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#if defined(CONFIG_EFI_VARS) || defined(CONFIG_EFI_VARS_MODULE)
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int efivars_sysfs_init(void);
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#define EFIVARS_DATA_SIZE_MAX 1024
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#endif /* CONFIG_EFI_VARS */
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#endif /* _LINUX_EFI_H */
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