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SubjectRE: [PATCH v3] efivars,efi-pstore: Hold off deletion of sysfs entry until, the scan is completed
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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@redhat.com]
> Sent: Thursday, October 17, 2013 11:07 AM
> To: Madper Xie
> Cc: Seiji Aguchi; linux-kernel@vger.kernel.org; linux-efi@vger.kernel.org; matt.fleming@intel.com; tony.luck@intel.com; Tomoki
> Sekiyama; dle-develop@lists.sourceforge.net
> 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@redhat.com writes:
>
> > Oops, It seems my mu4e(a email client for emacs)'s auto-indent breaks the
> > patch... I apologize for this...
> >
> > seiji.aguchi@hds.com 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@redhat.com]
> >>> Sent: Thursday, October 17, 2013 1:54 AM
> >>> To: Seiji Aguchi
> >>> Cc: linux-kernel@vger.kernel.org; linux-efi@vger.kernel.org; matt.fleming@intel.com; tony.luck@intel.com; Tomoki Sekiyama;
> dle-
> >>> develop@lists.sourceforge.net
> >>> 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@hds.com 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@hds.com>
> >>> > ---
> >>> > 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.


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