add releasepage hooks to block devices which can be used by file systems
Implement blkdev_releasepage() to release the buffer_heads and pages
after we release private data belonging to a mounted filesystem.
Cc: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 349a26c..1dd07e6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1220,6 +1220,20 @@
return blkdev_ioctl(bdev, mode, cmd, arg);
}
+/*
+ * Try to release a page associated with block device when the system
+ * is under memory pressure.
+ */
+static int blkdev_releasepage(struct page *page, gfp_t wait)
+{
+ struct super_block *super = BDEV_I(page->mapping->host)->bdev.bd_super;
+
+ if (super && super->s_op->bdev_try_to_free_page)
+ return super->s_op->bdev_try_to_free_page(super, page, wait);
+
+ return try_to_free_buffers(page);
+}
+
static const struct address_space_operations def_blk_aops = {
.readpage = blkdev_readpage,
.writepage = blkdev_writepage,
@@ -1227,6 +1241,7 @@
.write_begin = blkdev_write_begin,
.write_end = blkdev_write_end,
.writepages = generic_writepages,
+ .releasepage = blkdev_releasepage,
.direct_IO = blkdev_direct_IO,
};
diff --git a/fs/super.c b/fs/super.c
index ddba069..d5fd449 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -800,6 +800,7 @@
}
s->s_flags |= MS_ACTIVE;
+ bdev->bd_super = s;
}
return simple_set_mnt(mnt, s);
@@ -819,6 +820,7 @@
struct block_device *bdev = sb->s_bdev;
fmode_t mode = sb->s_mode;
+ bdev->bd_super = 0;
generic_shutdown_super(sb);
sync_blockdev(bdev);
close_bdev_exclusive(bdev, mode);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f2a30101..0f54ae0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -565,6 +565,7 @@
struct block_device {
dev_t bd_dev; /* not a kdev_t - it's a search key */
struct inode * bd_inode; /* will die */
+ struct super_block * bd_super;
int bd_openers;
struct mutex bd_mutex; /* open/close mutex */
struct semaphore bd_mount_sem;
@@ -1385,6 +1386,7 @@
ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
#endif
+ int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
};
/*