From: Theodore Ts'o Subject: [PATCH -V2] ext3: provide function to release metadata pages under memory pressure Date: Mon, 8 Dec 2008 09:06:42 -0500 Message-ID: <1228745203-743-1-git-send-email-tytso@mit.edu> References: <20081208140138.GA17700@mit.edu> Cc: aneesh.kumar@linux.vnet.ibm.com, balbir@linux.vnet.ibm.com, Toshiyuki Okajima , "Theodore Ts'o" , linux-fsdevel@vger.kernel.org To: Ext4 Developers List Return-path: Received: from www.church-of-our-saviour.org ([69.25.196.31]:60198 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751792AbYLHOGs (ORCPT ); Mon, 8 Dec 2008 09:06:48 -0500 In-Reply-To: <20081208140138.GA17700@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Toshiyuki Okajima Pages in the page cache belonging to ext3 data files are released via the ext3_releasepage() function specified in the ext3 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 is called by the block device's blkdev_releasepage() function, which calls journal_try_to_free_buffers() function to free the metadata. Signed-off-by: Toshiyuki Okajima Signed-off-by: "Theodore Ts'o" Cc: linux-fsdevel@vger.kernel.org --- fs/ext3/inode.c | 29 +++++++++++++++++++++++++++++ fs/ext3/super.c | 2 ++ include/linux/ext3_fs.h | 2 ++ 3 files changed, 33 insertions(+), 0 deletions(-) diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c index f8424ad..89c065a 100644 --- a/fs/ext3/inode.c +++ b/fs/ext3/inode.c @@ -1680,6 +1680,35 @@ static int ext3_releasepage(struct page *page, gfp_t wait) } /* + * 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 + * jbd layer's try_to_free_buffers() function to release them. + * + * Note: we have to strip the __GFP_WAIT flag before calling + * journal_try_to_free_buffers because blkdev_releasepage is + * called while holding a spinlock (bdev_inode.client_lock). + * Fortunately the metadata buffers we are interested are freed right + * away and do not require calling journal_wait_for_transaction_sync_data(). + */ +int ext3_release_metadata(void *client, struct page *page, gfp_t wait) +{ + struct super_block *sb = (struct super_block*)client; + journal_t *journal; + + WARN_ON(PageChecked(page)); + if (!page_has_buffers(page)) + return 0; + BUG_ON(EXT3_SB(sb) == NULL); + journal = EXT3_SB(sb)->s_journal; + if (journal != NULL) + return journal_try_to_free_buffers(journal, page, + wait & ~__GFP_WAIT); + else + return try_to_free_buffers(page); +} + +/* * If the O_DIRECT write will extend the file then add this inode to the * orphan list. So recovery will truncate it back to the original size * if the machine crashes during the write. diff --git a/fs/ext3/super.c b/fs/ext3/super.c index 541d5e4..4428149 100644 --- a/fs/ext3/super.c +++ b/fs/ext3/super.c @@ -2981,6 +2981,8 @@ static struct file_system_type ext3_fs_type = { .name = "ext3", .get_sb = ext3_get_sb, .kill_sb = kill_block_super, + .release_metadata + = ext3_release_metadata, .fs_flags = FS_REQUIRES_DEV, }; diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h index 9004794..3e3052f 100644 --- a/include/linux/ext3_fs.h +++ b/include/linux/ext3_fs.h @@ -867,6 +867,8 @@ extern void ext3_get_inode_flags(struct ext3_inode_info *); extern void ext3_set_aops(struct inode *inode); extern int ext3_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, u64 start, u64 len); +extern int ext3_release_metadata(void *client, struct page *page, + gfp_t wait); /* ioctl.c */ extern int ext3_ioctl (struct inode *, struct file *, unsigned int, -- 1.6.0.4.8.g36f27.dirty