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Date: Wed, 12 Nov 2008 16:51:54 +0900
From: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To: akpm@...ux-foundation.org, tytso@....edu, viro@...iv.linux.org.uk,
sct@...hat.com, adilger@....com
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 1/3][RFC] vfs: release block-device-mapping buffer_heads
which have the filesystem private data for avoiding oom-killer
[PATCH 1/3] vfs: release block-device-mapping buffer_heads which have the filesystem
private data for avoiding oom-killer
Implement blkdev_releasepage() to release the buffer_heads and page after we
release private data which are a client's. One of the clients is a filesystem.
blkdev_releasepage() can call the client's releasepage() which is registered
by blkdev_register_client_releasepage() to release its private data.
Signed-off-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
---
fs/block_dev.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/super.c | 22 ++++++++++++++++++
include/linux/fs.h | 9 +++++++
3 files changed, 93 insertions(+)
diff -Nurp linux-2.6.28-rc4.orig/fs/block_dev.c linux-2.6.28-rc4/fs/block_dev.c
--- linux-2.6.28-rc4.orig/fs/block_dev.c 2008-11-10 09:36:15.000000000 +0900
+++ linux-2.6.28-rc4/fs/block_dev.c 2008-11-10 18:33:52.000000000 +0900
@@ -29,6 +29,9 @@
struct bdev_inode {
struct block_device bdev;
+ void *client;
+ int (*client_releasepage)(void*, struct page*, gfp_t);
+ rwlock_t client_lock;
struct inode vfs_inode;
};
@@ -260,6 +263,9 @@ static struct inode *bdev_alloc_inode(st
struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
if (!ei)
return NULL;
+ ei->client = NULL;
+ ei->client_releasepage = NULL;
+ rwlock_init(&ei->client_lock);
return &ei->vfs_inode;
}
@@ -1208,6 +1214,61 @@ static long block_ioctl(struct file *fil
return blkdev_ioctl(bdev, mode, cmd, arg);
}
+/*
+ * blkdev_releasepage: execute ei->client_releasepage() if it exists.
+ * Otherwise, execute try_to_free_buffers().
+ * ei->client_releasepage() releases private client's page if possible.
+ * Because a buffer_head's using counter is bigger than 0 if a client has
+ * a page for private usage. If so, try_to_free_buffers() cannot release it.
+ * Therefore a client must try to release a page itself.
+ */
+static int blkdev_releasepage(struct page *page, gfp_t wait)
+{
+ struct bdev_inode *ei = BDEV_I(page->mapping->host);
+ int ret;
+
+ read_lock(&ei->client_lock);
+ if (ei->client_releasepage != NULL)
+ ret = (*ei->client_releasepage)(ei->client, page, wait);
+ else
+ ret = try_to_free_buffers(page);
+ read_unlock(&ei->client_lock);
+ return ret;
+}
+
+/*
+ * blkdev_register_client_releasepage: register client_releasepage.
+ */
+int blkdev_register_client_releasepage(struct block_device *bdev,
+ void *client, int (*releasepage)(void*, struct page*, gfp_t))
+{
+ struct bdev_inode *ei = BDEV_I(bdev->bd_inode);
+ int ret = 1;
+
+ write_lock(&ei->client_lock);
+ if (ei->client == NULL && ei->client_releasepage == NULL) {
+ ei->client = client;
+ ei->client_releasepage = releasepage;
+ } else if (ei->client != client
+ || ei->client_releasepage != releasepage)
+ ret = 0;
+ write_unlock(&ei->client_lock);
+ return ret;
+}
+
+/*
+ * blkdev_unregister_client_releasepage: unregister client_releasepage.
+ */
+void blkdev_unregister_client_releasepage(struct block_device *bdev)
+{
+ struct bdev_inode *ei = BDEV_I(bdev->bd_inode);
+
+ write_lock(&ei->client_lock);
+ ei->client = NULL;
+ ei->client_releasepage = NULL;
+ write_unlock(&ei->client_lock);
+}
+
static const struct address_space_operations def_blk_aops = {
.readpage = blkdev_readpage,
.writepage = blkdev_writepage,
@@ -1215,6 +1276,7 @@ static const struct address_space_operat
.write_begin = blkdev_write_begin,
.write_end = blkdev_write_end,
.writepages = generic_writepages,
+ .releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
};
diff -Nurp linux-2.6.28-rc4.orig/fs/super.c linux-2.6.28-rc4/fs/super.c
--- linux-2.6.28-rc4.orig/fs/super.c 2008-11-10 09:36:15.000000000 +0900
+++ linux-2.6.28-rc4/fs/super.c 2008-11-11 09:25:04.000000000 +0900
@@ -801,6 +801,18 @@ int get_sb_bdev(struct file_system_type
s->s_flags |= MS_ACTIVE;
}
+ /*
+ * register a client function which releases a page whose mapping is
+ * block device
+ */
+ if (fs_type->release_metadata != NULL
+ && !blkdev_register_client_releasepage(bdev, s,
+ fs_type->release_metadata)) {
+ up_write(&s->s_umount);
+ deactivate_super(s);
+ error = -EBUSY;
+ goto error_bdev;
+ }
return simple_set_mnt(mnt, s);
@@ -819,6 +831,16 @@ void kill_block_super(struct super_block
struct block_device *bdev = sb->s_bdev;
fmode_t mode = sb->s_mode;
+ /*
+ * unregister a client function which releases a page whose mapping is
+ * block device
+ *
+ * This is sure to be unmounting here, and it releases all own data
+ * itself. Therefore the filesystem's function which is owned by the
+ * block device, which releases its data is not needed any more.
+ */
+ if (sb->s_type->release_metadata != NULL)
+ blkdev_unregister_client_releasepage(bdev);
generic_shutdown_super(sb);
sync_blockdev(bdev);
close_bdev_exclusive(bdev, mode);
diff -Nurp linux-2.6.28-rc4.orig/include/linux/fs.h linux-2.6.28-rc4/include/linux/fs.h
--- linux-2.6.28-rc4.orig/include/linux/fs.h 2008-11-10 09:36:15.000000000 +0900
+++ linux-2.6.28-rc4/include/linux/fs.h 2008-11-11 09:01:12.000000000 +0900
@@ -1538,6 +1538,7 @@ struct file_system_type {
int (*get_sb) (struct file_system_type *, int,
const char *, void *, struct vfsmount *);
void (*kill_sb) (struct super_block *);
+ int (*release_metadata)(void*, struct page*, gfp_t);
struct module *owner;
struct file_system_type * next;
struct list_head fs_supers;
@@ -1699,8 +1700,16 @@ extern void bd_set_size(struct block_dev
extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
extern struct block_device *open_by_devnum(dev_t, fmode_t);
+extern int blkdev_register_client_releasepage(struct block_device *,
+ void *, int (*releasepage)(void *, struct page*, gfp_t));
+extern void blkdev_unregister_client_releasepage(struct block_device *);
#else
static inline void bd_forget(struct inode *inode) {}
+static inline int blkdev_register_client_releasepage(struct block_device *,
+ void *, int (*releasepage)(void *, struct page*, gfp_t))
+{ return 1; }
+static inline void blkdev_unregister_client_releasepage(struct block_device *)
+{}
#endif
extern const struct file_operations def_blk_fops;
extern const struct file_operations def_chr_fops;
--
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