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ext4: provide function to release metadata pages under memory pressure

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Pages in the page cache belonging to ext4 data files are released via
the ext4_releasepage() function specified in the ext4 inode's
address_space_ops.  However, metadata blocks (such as indirect blocks,
directory blocks, etc) are managed via the block device
address_space_ops, and they can not be released by
try_to_free_buffers() if they have a journal head attached to them.

To address this, we supply a release_metadata function which calls
jbd2_journal_try_to_free_buffers() function to free the metadata, and
which is called by the block device's blkdev_releasepage() function.

Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-fsdevel@vger.kernel.org
This commit is contained in:
Toshiyuki Okajima 2009-01-05 22:38:48 -05:00 committed by Theodore Ts'o
parent 6b082b5312
commit c39a7f84d7
1 changed files with 20 additions and 0 deletions
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20
fs/ext4/super.c
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@ -907,6 +907,25 @@ static struct dentry *ext4_fh_to_parent(struct super_block *sb, struct fid *fid,
ext4_nfs_get_inode);
}
/*
* Try to release metadata pages (indirect blocks, directories) which are
* mapped via the block device. Since these pages could have journal heads
* which would prevent try_to_free_buffers() from freeing them, we must use
* jbd2 layer's try_to_free_buffers() function to release them.
*/
static int bdev_try_to_free_page(struct super_block *sb, struct page *page, gfp_t wait)
{
journal_t *journal = EXT4_SB(sb)->s_journal;
WARN_ON(PageChecked(page));
if (!page_has_buffers(page))
return 0;
if (journal)
return jbd2_journal_try_to_free_buffers(journal, page,
wait & ~__GFP_WAIT);
return try_to_free_buffers(page);
}
#ifdef CONFIG_QUOTA
#define QTYPE2NAME(t) ((t) == USRQUOTA ? "user" : "group")
#define QTYPE2MOPT(on, t) ((t) == USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))
@ -971,6 +990,7 @@ static const struct super_operations ext4_sops = {
.quota_read = ext4_quota_read,
.quota_write = ext4_quota_write,
#endif
.bdev_try_to_free_page = bdev_try_to_free_page,
};
static const struct export_operations ext4_export_ops = {