From: Eric Sandeen Subject: [PATCH, RFC V2] ext4: flush delalloc blocks when space is low Date: Wed, 21 Oct 2009 14:51:04 -0500 Message-ID: <4ADF6628.9080105@redhat.com> References: <4ADE24CF.1080906@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: ext4 development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:17620 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754128AbZJUTvB (ORCPT ); Wed, 21 Oct 2009 15:51:01 -0400 Received: from int-mx08.intmail.prod.int.phx2.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n9LJp5JM014508 for ; Wed, 21 Oct 2009 15:51:05 -0400 Received: from neon.msp.redhat.com (neon.msp.redhat.com [10.15.80.10]) by int-mx08.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id n9LJp5H6012104 for ; Wed, 21 Oct 2009 15:51:05 -0400 In-Reply-To: <4ADE24CF.1080906@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Creating many small files in rapid succession on a small filesystem can lead to spurious ENOSPC; on a 104MB filesystem: for i in `seq 1 22500`; do echo -n > $SCRATCH_MNT/$i echo XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX > $SCRATCH_MNT/$i done leads to ENOSPC even though after a sync, 40% of the fs is free again. This is because we reserve worst-case metadata for delalloc writes, and when data is allocated that worst-case reservation was not needed. I've added 2 flushers here: * when free space is low compared to dirty blocks, do an async flush * when we get a hard ENOSPC, do a sync flush before retry This resolves the testcase for me, and survives all 4 generic ENOSPC tests in xfstests. V2: don't try to sync if we're still in a (probably nested) transaction. Thanks to Josef for pointing out that possibility. Signed-off-by: Eric Sandeen --- diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 1d04189..28bde58 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -605,11 +605,27 @@ int ext4_claim_free_blocks(struct ext4_sb_info *sbi, */ int ext4_should_retry_alloc(struct super_block *sb, int *retries) { - if (!ext4_has_free_blocks(EXT4_SB(sb), 1) || + s64 dirtyblocks = 0; + struct percpu_counter *dbc = &EXT4_SB(sb)->s_dirtyblocks_counter; + + if (test_opt(sb, DELALLOC)) + dirtyblocks = percpu_counter_read_positive(dbc); + + if ((!ext4_has_free_blocks(EXT4_SB(sb), 1) && !dirtyblocks) || (*retries)++ > 3 || !EXT4_SB(sb)->s_journal) return 0; + /* try a sync to flush delalloc space & free resvd metadata */ + if (!ext4_has_free_blocks(EXT4_SB(sb), 1) && dirtyblocks) { + if (!ext4_journal_current_handle()) { + down_read(&sb->s_umount); + sync_inodes_sb(sb); + up_read(&sb->s_umount); + return 1; + } + } + jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id); return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 5c5bc5d..27c8b9b 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3024,11 +3024,18 @@ static int ext4_nonda_switch(struct super_block *sb) if (2 * free_blocks < 3 * dirty_blocks || free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) { /* - * free block count is less that 150% of dirty blocks - * or free blocks is less that watermark + * free block count is less than 150% of dirty blocks + * or free blocks is less than watermark */ return 1; } + /* + * Even if we don't switch but are nearing capacity, + * start pushing delalloc when 1/2 of free blocks are dirty. + */ + if (free_blocks < 2 * dirty_blocks) + writeback_inodes_sb(sb); + return 0; }