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Message-ID: <87y6j9qlwq.fsf@linux.vnet.ibm.com>
Date: Thu, 04 Feb 2010 16:59:25 +0530
From: "Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To: Dmitry Monakhov <dmonakhov@...nvz.org>, linux-ext4@...r.kernel.org
Cc: tytso@....edu
Subject: Re: [PATCH 2/2] ext4: fix delalloc retry loop logic v2
On Wed, 03 Feb 2010 22:07:03 +0300, Dmitry Monakhov <dmonakhov@...nvz.org> wrote:
> Dmitry Monakhov <dmonakhov@...nvz.org> writes:
>
> > Theodore please review this patch ASAP, currently ext4+quota is
> > fatally broken due to your patch. Christmas holidays when you
> > submit your patch is not good time for good review, IMHO
> > i was too lazy to review it carefully.
> > Testcase is trivial it is enough just hit a quota barrier.
> > dmon$ set-quota-limit /mnt id=dmon --bsoft=1000 --bsoft=1000
> > dmon$ dd if=/dev/zefo of=/mnt/file
> >
> > kernel BUG at fs/jbd2/transaction.c:1027!
> OOps, i'm sorry. seems that i've send wrong patch version
> the only difference is follows:
> - dqretry = (ret == -EDQUOT) || EXT4_I(inode)->i_reserved_meta_blocks;
> + dqretry = (ret == -EDQUOT) && EXT4_I(inode)->i_reserved_meta_blocks;
> Correct version attached.
> From 3dd53f88470fdc4ec3f06da34cfc760fa8359be8 Mon Sep 17 00:00:00 2001
> From: Dmitry Monakhov <dmonakhov@...nvz.org>
> Date: Wed, 3 Feb 2010 22:03:17 +0300
> Subject: [PATCH 2/2] ext4: fix delalloc retry loop logic -v2
>
> Current delalloc write path is broken:
> ext4_da_write_begin()
> ext4_journal_start(inode, 1); -> current->journal != NULL
> block_write_begin
> ext4_da_get_block_prep()
> ext4_da_reserve_space()
> ext4_should_retry_alloc() -> deadlock
> write_inode_now() -> BUG_ON due to lack of journal credits
>
> Bug was partly introduced by following commit:
> 0637c6f4135f592f094207c7c21e7c0fc5557834
> ext4: Patch up how we claim metadata blocks for quota purposes
> In order to preserve retry logic and eliminate bugs we have to
> move retry loop to ext4_da_write_begin()
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
> fs/ext4/inode.c | 41 ++++++++++++++++++-----------------------
> 1 files changed, 18 insertions(+), 23 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 2d3fe4d..bd9e573 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1815,7 +1815,6 @@ static int ext4_journalled_write_end(struct file *file,
> */
> static int ext4_da_reserve_space(struct inode *inode, sector_t lblock)
> {
> - int retries = 0;
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> struct ext4_inode_info *ei = EXT4_I(inode);
> unsigned long md_needed, md_reserved;
> @@ -1825,7 +1824,6 @@ static int ext4_da_reserve_space(struct inode *inode, sector_t lblock)
> * in order to allocate nrblocks
> * worse case is one extent per block
> */
> -repeat:
> spin_lock(&ei->i_block_reservation_lock);
> md_reserved = ei->i_reserved_meta_blocks;
> md_needed = ext4_calc_metadata_amount(inode, lblock);
> @@ -1836,27 +1834,11 @@ repeat:
> * later. Real quota accounting is done at pages writeout
> * time.
> */
> - if (vfs_dq_reserve_block(inode, md_needed + 1)) {
> - /*
> - * We tend to badly over-estimate the amount of
> - * metadata blocks which are needed, so if we have
> - * reserved any metadata blocks, try to force out the
> - * inode and see if we have any better luck.
> - */
> - if (md_reserved && retries++ <= 3)
> - goto retry;
> + if (vfs_dq_reserve_block(inode, md_needed + 1))
> return -EDQUOT;
> - }
>
> if (ext4_claim_free_blocks(sbi, md_needed + 1)) {
> vfs_dq_release_reservation_block(inode, md_needed + 1);
> - if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
> - retry:
> - if (md_reserved)
> - write_inode_now(inode, (retries == 3));
> - yield();
> - goto repeat;
> - }
> return -ENOSPC;
> }
> spin_lock(&ei->i_block_reservation_lock);
> @@ -3033,7 +3015,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
> loff_t pos, unsigned len, unsigned flags,
> struct page **pagep, void **fsdata)
> {
> - int ret, retries = 0;
> + int ret, dqretry, retries = 0;
> struct page *page;
> pgoff_t index;
> unsigned from, to;
> @@ -3090,9 +3072,22 @@ retry:
> ext4_truncate_failed_write(inode);
> }
>
> - if (!(flags & EXT4_AOP_FLAG_NORETRY) &&
> - ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
> - goto retry;
> + dqretry = (ret == -EDQUOT) && EXT4_I(inode)->i_reserved_meta_blocks;
> + if ( !(flags & EXT4_AOP_FLAG_NORETRY) &&
> + (ret == -ENOSPC || dqretry) &&
> + ext4_should_retry_alloc(inode->i_sb, &retries)) {
> + if (dqretry) {
> + /*
> + * We tend to badly over-estimate the amount of
> + * metadata blocks which are needed, so if we have
> + * reserved any metadata blocks, try to force out the
> + * inode and see if we have any better luck.
> + */
> + write_inode_now(inode, (retries == 3));
> + }
> + yield();
> + goto retry;
> + }
> out:
> return ret;
> }
Where is EXT4_AOP_FLAG_NORETRY defined ?. I have submitted a different
version of the patch and it is already upstream with commit
1db913823c0f8360fccbd24ca67eb073966a5ffd
-aneesh
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