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Message-Id: <20180621212835.5636-6-willy@infradead.org>
Date: Thu, 21 Jun 2018 14:28:14 -0700
From: Matthew Wilcox <willy@...radead.org>
To: linux-kernel@...r.kernel.org
Cc: Matthew Wilcox <willy@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org
Subject: [PATCH 05/26] fs: Convert unnamed_dev_ida to new API
The new API is much easier for this user. Also add kerneldoc for
get_anon_bdev().
Signed-off-by: Matthew Wilcox <willy@...radead.org>
---
fs/super.c | 63 +++++++++++++++++++-----------------------------------
1 file changed, 22 insertions(+), 41 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 50728d9c1a05..3e7a0aea716a 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -978,58 +978,42 @@ void emergency_thaw_all(void)
}
}
-/*
- * Unnamed block devices are dummy devices used by virtual
- * filesystems which don't use real block-devices. -- jrs
- */
-
static DEFINE_IDA(unnamed_dev_ida);
-static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
-/* Many userspace utilities consider an FSID of 0 invalid.
- * Always return at least 1 from get_anon_bdev.
- */
-static int unnamed_dev_start = 1;
+/**
+ * get_anon_bdev - Allocate a block device for filesystems which don't have one.
+ * @p: Pointer to a dev_t.
+ *
+ * Filesystems which don't use real block devices can call this function
+ * to allocate a virtual block device.
+ *
+ * Context: Any context. Frequently called while holding sb_lock.
+ * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
+ * or -EAGAIN if memory allocation failed.
+ */
int get_anon_bdev(dev_t *p)
{
int dev;
- int error;
- retry:
- if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
- return -ENOMEM;
- spin_lock(&unnamed_dev_lock);
- error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
- if (!error)
- unnamed_dev_start = dev + 1;
- spin_unlock(&unnamed_dev_lock);
- if (error == -EAGAIN)
- /* We raced and lost with another CPU. */
- goto retry;
- else if (error)
+ /*
+ * Many userspace utilities consider an FSID of 0 invalid.
+ * Always return at least 1 from get_anon_bdev.
+ */
+ dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
+ GFP_ATOMIC);
+ if (dev == -ENOSPC)
+ return -EMFILE;
+ if (dev < 0)
return -EAGAIN;
- if (dev >= (1 << MINORBITS)) {
- spin_lock(&unnamed_dev_lock);
- ida_remove(&unnamed_dev_ida, dev);
- if (unnamed_dev_start > dev)
- unnamed_dev_start = dev;
- spin_unlock(&unnamed_dev_lock);
- return -EMFILE;
- }
- *p = MKDEV(0, dev & MINORMASK);
+ *p = MKDEV(0, dev);
return 0;
}
EXPORT_SYMBOL(get_anon_bdev);
void free_anon_bdev(dev_t dev)
{
- int slot = MINOR(dev);
- spin_lock(&unnamed_dev_lock);
- ida_remove(&unnamed_dev_ida, slot);
- if (slot < unnamed_dev_start)
- unnamed_dev_start = slot;
- spin_unlock(&unnamed_dev_lock);
+ ida_free(&unnamed_dev_ida, MINOR(dev));
}
EXPORT_SYMBOL(free_anon_bdev);
@@ -1037,7 +1021,6 @@ int set_anon_super(struct super_block *s, void *data)
{
return get_anon_bdev(&s->s_dev);
}
-
EXPORT_SYMBOL(set_anon_super);
void kill_anon_super(struct super_block *sb)
@@ -1046,7 +1029,6 @@ void kill_anon_super(struct super_block *sb)
generic_shutdown_super(sb);
free_anon_bdev(dev);
}
-
EXPORT_SYMBOL(kill_anon_super);
void kill_litter_super(struct super_block *sb)
@@ -1055,7 +1037,6 @@ void kill_litter_super(struct super_block *sb)
d_genocide(sb->s_root);
kill_anon_super(sb);
}
-
EXPORT_SYMBOL(kill_litter_super);
static int ns_test_super(struct super_block *sb, void *data)
--
2.17.1
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