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Message-ID: <20250327140613.25178-5-James.Bottomley@HansenPartnership.com>
Date: Thu, 27 Mar 2025 10:06:13 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: mcgrof@...nel.org,
jack@...e.cz,
hch@...radead.org,
david@...morbit.com,
rafael@...nel.org,
djwong@...nel.org,
pavel@...nel.org,
peterz@...radead.org,
mingo@...hat.com,
will@...nel.org,
boqun.feng@...il.com
Subject: [RFC PATCH 4/4] vfs: add filesystem freeze/thaw callbacks for power management
Introduce a freeze function, which iterates superblocks in reverse
order freezing filesystems. The indicator a filesystem is freezable
is either possessing a s_bdev or a freeze_super method. So this can
be used in efivarfs, whether the freeze is for hibernate is also
passed in via the new FREEZE_FOR_HIBERNATE flag.
Thawing is done opposite to freezing (so superblock traversal in
regular order) and the whole thing is plumbed into power management.
The original ksys_sync() is preserved so the whole freezing step is
optional (if it fails we're no worse off than we are today) so it
doesn't inhibit suspend/hibernate if there's a failure.
Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
---
fs/super.c | 61 ++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 5 ++++
kernel/power/hibernate.c | 12 ++++++++
kernel/power/suspend.c | 4 +++
4 files changed, 82 insertions(+)
diff --git a/fs/super.c b/fs/super.c
index 76785509d906..b4b0986414b0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1461,6 +1461,67 @@ static struct super_block *get_bdev_super(struct block_device *bdev)
return sb;
}
+/*
+ * Kernel freezing and thawing is only done in the power management
+ * subsystem and is thus single threaded (so we don't have to worry
+ * here about multiple calls to filesystems_freeze/thaw().
+ */
+
+static int freeze_flags;
+
+static void filesystems_freeze_callback(struct super_block *sb)
+{
+ /* errors don't fail suspend so ignore them */
+ if (sb->s_op->freeze_super)
+ sb->s_op->freeze_super(sb, FREEZE_MAY_NEST
+ | FREEZE_HOLDER_KERNEL
+ | freeze_flags);
+ else if (sb->s_bdev)
+ freeze_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL
+ | freeze_flags);
+ else {
+ pr_info("Ignoring filesystem %s\n", sb->s_type->name);
+ return;
+ }
+
+ pr_info("frozen %s, now syncing block ...", sb->s_type->name);
+ sync_blockdev(sb->s_bdev);
+ pr_info("done.");
+}
+
+/**
+ * filesystems_freeze - freeze callback for power management
+ *
+ * Freeze all active filesystems (in reverse superblock order)
+ */
+void filesystems_freeze(bool for_hibernate)
+{
+ freeze_flags = for_hibernate ? FREEZE_FOR_HIBERNATE : 0;
+ __iterate_supers_rev(filesystems_freeze_callback);
+}
+
+static void filesystems_thaw_callback(struct super_block *sb)
+{
+ if (sb->s_op->thaw_super)
+ sb->s_op->thaw_super(sb, FREEZE_MAY_NEST
+ | FREEZE_HOLDER_KERNEL
+ | freeze_flags);
+ else if (sb->s_bdev)
+ thaw_super(sb, FREEZE_MAY_NEST | FREEZE_HOLDER_KERNEL
+ | freeze_flags);
+}
+
+/**
+ * filesystems_thaw - thaw callback for power management
+ *
+ * Thaw all active filesystems (in forward superblock order)
+ */
+void filesystems_thaw(bool for_hibernate)
+{
+ freeze_flags = for_hibernate ? FREEZE_FOR_HIBERNATE : 0;
+ __iterate_supers(filesystems_thaw_callback);
+}
+
/**
* fs_bdev_freeze - freeze owning filesystem of block device
* @bdev: block device
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cbbb704eff74..de154e9379ec 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2272,6 +2272,7 @@ extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
* @FREEZE_HOLDER_KERNEL: kernel wants to freeze or thaw filesystem
* @FREEZE_HOLDER_USERSPACE: userspace wants to freeze or thaw filesystem
* @FREEZE_MAY_NEST: whether nesting freeze and thaw requests is allowed
+ * @FREEZE_FOR_HIBERNATE: set if freeze is from power management hibernate
*
* Indicate who the owner of the freeze or thaw request is and whether
* the freeze needs to be exclusive or can nest.
@@ -2285,6 +2286,7 @@ enum freeze_holder {
FREEZE_HOLDER_KERNEL = (1U << 0),
FREEZE_HOLDER_USERSPACE = (1U << 1),
FREEZE_MAY_NEST = (1U << 2),
+ FREEZE_FOR_HIBERNATE = (1U << 3),
};
struct super_operations {
@@ -3919,4 +3921,7 @@ static inline bool vfs_empty_path(int dfd, const char __user *path)
int generic_atomic_write_valid(struct kiocb *iocb, struct iov_iter *iter);
+void filesystems_freeze(bool for_hibernate);
+void filesystems_thaw(bool for_hibernate);
+
#endif /* _LINUX_FS_H */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 10a01af63a80..fc2106e6685a 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -778,7 +778,12 @@ int hibernate(void)
ksys_sync_helper();
+ pr_info("about to freeze filesystems\n");
+ filesystems_freeze(true);
+ pr_info("filesystem freeze done\n");
+
error = freeze_processes();
+ pr_info("process freeze done\n");
if (error)
goto Exit;
@@ -788,7 +793,9 @@ int hibernate(void)
if (error)
goto Thaw;
+ pr_info("About to create snapshot\n");
error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
+ pr_info("snapshot done\n");
if (error || freezer_test_done)
goto Free_bitmaps;
@@ -842,6 +849,8 @@ int hibernate(void)
}
thaw_processes();
+ filesystems_thaw(true);
+
/* Don't bother checking whether freezer_test_done is true */
freezer_test_done = false;
Exit:
@@ -939,6 +948,8 @@ int hibernate_quiet_exec(int (*func)(void *data), void *data)
thaw_processes();
+ filesystems_thaw(true);
+
exit:
pm_notifier_call_chain(PM_POST_HIBERNATION);
@@ -1041,6 +1052,7 @@ static int software_resume(void)
error = load_image_and_restore();
thaw_processes();
+ filesystems_thaw(true);
Finish:
pm_notifier_call_chain(PM_POST_RESTORE);
Restore:
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 09f8397bae15..34cc5b0c408c 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -544,6 +544,7 @@ int suspend_devices_and_enter(suspend_state_t state)
static void suspend_finish(void)
{
suspend_thaw_processes();
+ filesystems_thaw(false);
pm_notifier_call_chain(PM_POST_SUSPEND);
pm_restore_console();
}
@@ -581,6 +582,7 @@ static int enter_state(suspend_state_t state)
trace_suspend_resume(TPS("sync_filesystems"), 0, true);
ksys_sync_helper();
trace_suspend_resume(TPS("sync_filesystems"), 0, false);
+ filesystems_freeze(false);
}
pm_pr_dbg("Preparing system for sleep (%s)\n", mem_sleep_labels[state]);
@@ -603,6 +605,8 @@ static int enter_state(suspend_state_t state)
pm_pr_dbg("Finishing wakeup.\n");
suspend_finish();
Unlock:
+ if (sync_on_suspend_enabled)
+ filesystems_thaw(false);
mutex_unlock(&system_transition_mutex);
return error;
}
--
2.43.0
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