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Date: Wed, 29 Nov 2017 15:23:46 -0800
From: "Luis R. Rodriguez" <mcgrof@...nel.org>
To: viro@...iv.linux.org.uk, bart.vanassche@....com,
ming.lei@...hat.com, tytso@....edu, darrick.wong@...cle.com,
jikos@...nel.org, rjw@...ysocki.net, pavel@....cz,
len.brown@...el.com, linux-fsdevel@...r.kernel.org
Cc: boris.ostrovsky@...cle.com, jgross@...e.com,
todd.e.brandt@...ux.intel.com, nborisov@...e.com, jack@...e.cz,
martin.petersen@...cle.com, ONeukum@...e.com,
oleksandr@...alenko.name, oleg.b.antonyan@...il.com,
yu.chen.surf@...il.com, dan.j.williams@...el.com,
linux-pm@...r.kernel.org, linux-block@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
"Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [PATCH 01/11] fs: provide unlocked helper for freeze_super()
freeze_super() holds a write lock, however we wish to also enable
callers which already hold the write lock. To do this provide a helper
and make freeze_super() use it. This way, all that freeze_super() does
now is lock handling and active count management.
This change has no functional changes.
Suggested-by: Dave Chinner <david@...morbit.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
fs/super.c | 100 +++++++++++++++++++++++++++++++++----------------------------
1 file changed, 55 insertions(+), 45 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index d4e33e8f1e6f..a7650ff22f0e 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1387,59 +1387,20 @@ static void sb_freeze_unlock(struct super_block *sb)
percpu_up_write(sb->s_writers.rw_sem + level);
}
-/**
- * freeze_super - lock the filesystem and force it into a consistent state
- * @sb: the super to lock
- *
- * Syncs the super to make sure the filesystem is consistent and calls the fs's
- * freeze_fs. Subsequent calls to this without first thawing the fs will return
- * -EBUSY.
- *
- * During this function, sb->s_writers.frozen goes through these values:
- *
- * SB_UNFROZEN: File system is normal, all writes progress as usual.
- *
- * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
- * writes should be blocked, though page faults are still allowed. We wait for
- * all writes to complete and then proceed to the next stage.
- *
- * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
- * but internal fs threads can still modify the filesystem (although they
- * should not dirty new pages or inodes), writeback can run etc. After waiting
- * for all running page faults we sync the filesystem which will clean all
- * dirty pages and inodes (no new dirty pages or inodes can be created when
- * sync is running).
- *
- * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
- * modification are blocked (e.g. XFS preallocation truncation on inode
- * reclaim). This is usually implemented by blocking new transactions for
- * filesystems that have them and need this additional guard. After all
- * internal writers are finished we call ->freeze_fs() to finish filesystem
- * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
- * mostly auxiliary for filesystems to verify they do not modify frozen fs.
- *
- * sb->s_writers.frozen is protected by sb->s_umount.
- */
-int freeze_super(struct super_block *sb)
+/* Caller takes lock and handles active count */
+static int freeze_locked_super(struct super_block *sb)
{
int ret;
- atomic_inc(&sb->s_active);
- down_write(&sb->s_umount);
- if (sb->s_writers.frozen != SB_UNFROZEN) {
- deactivate_locked_super(sb);
+ if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
- }
- if (!(sb->s_flags & SB_BORN)) {
- up_write(&sb->s_umount);
+ if (!(sb->s_flags & SB_BORN))
return 0; /* sic - it's "nothing to do" */
- }
if (sb_rdonly(sb)) {
/* Nothing to do really... */
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
- up_write(&sb->s_umount);
return 0;
}
@@ -1468,7 +1429,6 @@ int freeze_super(struct super_block *sb)
sb->s_writers.frozen = SB_UNFROZEN;
sb_freeze_unlock(sb);
wake_up(&sb->s_writers.wait_unfrozen);
- deactivate_locked_super(sb);
return ret;
}
}
@@ -1478,9 +1438,59 @@ int freeze_super(struct super_block *sb)
*/
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
lockdep_sb_freeze_release(sb);
- up_write(&sb->s_umount);
return 0;
}
+
+/**
+ * freeze_super - lock the filesystem and force it into a consistent state
+ * @sb: the super to lock
+ *
+ * Syncs the super to make sure the filesystem is consistent and calls the fs's
+ * freeze_fs. Subsequent calls to this without first thawing the fs will return
+ * -EBUSY.
+ *
+ * During this function, sb->s_writers.frozen goes through these values:
+ *
+ * SB_UNFROZEN: File system is normal, all writes progress as usual.
+ *
+ * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
+ * writes should be blocked, though page faults are still allowed. We wait for
+ * all writes to complete and then proceed to the next stage.
+ *
+ * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
+ * but internal fs threads can still modify the filesystem (although they
+ * should not dirty new pages or inodes), writeback can run etc. After waiting
+ * for all running page faults we sync the filesystem which will clean all
+ * dirty pages and inodes (no new dirty pages or inodes can be created when
+ * sync is running).
+ *
+ * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
+ * modification are blocked (e.g. XFS preallocation truncation on inode
+ * reclaim). This is usually implemented by blocking new transactions for
+ * filesystems that have them and need this additional guard. After all
+ * internal writers are finished we call ->freeze_fs() to finish filesystem
+ * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
+ * mostly auxiliary for filesystems to verify they do not modify frozen fs.
+ *
+ * sb->s_writers.frozen is protected by sb->s_umount.
+ */
+int freeze_super(struct super_block *sb)
+{
+ int error;
+
+ atomic_inc(&sb->s_active);
+
+ down_write(&sb->s_umount);
+ error = freeze_locked_super(sb);
+ if (error) {
+ deactivate_locked_super(sb);
+ goto out;
+ }
+ up_write(&sb->s_umount);
+
+out:
+ return error;
+}
EXPORT_SYMBOL(freeze_super);
/**
--
2.15.0
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