* [RFC PATCH 2/2] ext4: undo ei->i_da_metadata_calc_len increment if we fail to claim space
@ 2012-04-02 15:14 Brian Foster
2012-07-23 4:18 ` Theodore Ts'o
0 siblings, 1 reply; 3+ messages in thread
From: Brian Foster @ 2012-04-02 15:14 UTC (permalink / raw)
To: linux-ext4
From: Brian Foster <bfoster@redhat.com>
If we call ext4_calc_metadata_amount() and then fail to claim
the space, a subsequent successful request to a block covered
by the same ext2 indirect block will set md_needed to 0, fail
to update the associated counters and result in a delayed md
block allocation without a reservation. Decrement
i_da_metadata_calc_len on failure to ensure the next
reservation sets md_needed correctly.
Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/ext4/inode.c | 18 ++++++++++++++++--
1 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b58845c..7d2a3c0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1138,13 +1138,14 @@ repeat:
* We do still charge estimated metadata to the sb though;
* we cannot afford to run out of free blocks.
*/
- if (ext4_claim_free_clusters(sbi, md_needed + 1, 0)) {
+ ret = ext4_claim_free_clusters(sbi, md_needed + 1, 0);
+ if (ret) {
dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
yield();
goto repeat;
}
- return -ENOSPC;
+ goto error;
}
spin_lock(&ei->i_block_reservation_lock);
ei->i_reserved_data_blocks++;
@@ -1152,6 +1153,19 @@ repeat:
spin_unlock(&ei->i_block_reservation_lock);
return 0; /* success */
+
+error:
+ /*
+ * We've failed to reserve the space. Undo the effect
+ * of ext4_calc_metadata_amount() to ensure the next
+ * attempt correctly accounts for metadata.
+ */
+ spin_lock(&ei->i_block_reservation_lock);
+ if (ei->i_da_metadata_calc_len)
+ ei->i_da_metadata_calc_len--;
+ spin_unlock(&ei->i_block_reservation_lock);
+
+ return ret;
}
static void ext4_da_release_space(struct inode *inode, int to_free)
--
1.7.7.6
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH 2/2] ext4: undo ei->i_da_metadata_calc_len increment if we fail to claim space
2012-04-02 15:14 [RFC PATCH 2/2] ext4: undo ei->i_da_metadata_calc_len increment if we fail to claim space Brian Foster
@ 2012-07-23 4:18 ` Theodore Ts'o
2012-07-23 15:46 ` Brian Foster
0 siblings, 1 reply; 3+ messages in thread
From: Theodore Ts'o @ 2012-07-23 4:18 UTC (permalink / raw)
To: Brian Foster; +Cc: linux-ext4
On Mon, Apr 02, 2012 at 11:14:20AM -0400, Brian Foster wrote:
> From: Brian Foster <bfoster@redhat.com>
>
> If we call ext4_calc_metadata_amount() and then fail to claim
> the space, a subsequent successful request to a block covered
> by the same ext2 indirect block will set md_needed to 0, fail
> to update the associated counters and result in a delayed md
> block allocation without a reservation. Decrement
> i_da_metadata_calc_len on failure to ensure the next
> reservation sets md_needed correctly.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
Hi Brian,
This patch was not quite right. i_data_metadata_calc_len is not the
only side effect of ext4_calc_metadata(). We need to undo the side
effects not only when exit with an error, but also if we yield and
then retry the claim. Also, in the extent case we don't always modify
i_data_metadata_calc_len, so just decrementing isn't necessarily going
to do the right thing.
So this is the patch which I am testing....
- Ted
commit 19ec0f1fe139a642f688177ffd2f91a1c09f6bc0
Author: Theodore Ts'o <tytso@mit.edu>
Date: Mon Jul 23 00:00:20 2012 -0400
ext4: undo ext4_calc_metadata_amount if we fail to claim space
The function ext4_calc_metadata_amount() has side effects, although
it's not obvious from its function name. So if we fail to claim
space, regardless of whether we retry to claim the space again, or
return an error, we need to undo these side effects.
Otherwise we can end up incorrectly calculating the number of metadata
blocks needed for the operation, which was responsible for an xfstests
failure for test #271 when using an ext2 file system with delalloc
enabled.
Reported-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 25f809d..89b59cb 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1182,6 +1182,17 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
struct ext4_inode_info *ei = EXT4_I(inode);
unsigned int md_needed;
int ret;
+ ext4_lblk_t save_last_lblock;
+ int save_len;
+
+ /*
+ * We will charge metadata quota at writeout time; this saves
+ * us from metadata over-estimation, though we may go over by
+ * a small amount in the end. Here we just reserve for data.
+ */
+ ret = dquot_reserve_block(inode, EXT4_C2B(sbi, 1));
+ if (ret)
+ return ret;
/*
* recalculate the amount of metadata blocks to reserve
@@ -1190,32 +1201,31 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
*/
repeat:
spin_lock(&ei->i_block_reservation_lock);
+ /*
+ * ext4_calc_metadata_amount() has side effects, which we have
+ * to be prepared undo if we fail to claim space.
+ */
+ save_len = ei->i_da_metadata_calc_len;
+ save_last_lblock = ei->i_da_metadata_calc_last_lblock;
md_needed = EXT4_NUM_B2C(sbi,
ext4_calc_metadata_amount(inode, lblock));
trace_ext4_da_reserve_space(inode, md_needed);
- spin_unlock(&ei->i_block_reservation_lock);
/*
- * We will charge metadata quota at writeout time; this saves
- * us from metadata over-estimation, though we may go over by
- * a small amount in the end. Here we just reserve for data.
- */
- ret = dquot_reserve_block(inode, EXT4_C2B(sbi, 1));
- if (ret)
- return ret;
- /*
* We do still charge estimated metadata to the sb though;
* we cannot afford to run out of free blocks.
*/
if (ext4_claim_free_clusters(sbi, md_needed + 1, 0)) {
- dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
+ ei->i_da_metadata_calc_len = save_len;
+ ei->i_da_metadata_calc_last_lblock = save_last_lblock;
+ spin_unlock(&ei->i_block_reservation_lock);
if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
yield();
goto repeat;
}
+ dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
return -ENOSPC;
}
- spin_lock(&ei->i_block_reservation_lock);
ei->i_reserved_data_blocks++;
ei->i_reserved_meta_blocks += md_needed;
spin_unlock(&ei->i_block_reservation_lock);
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH 2/2] ext4: undo ei->i_da_metadata_calc_len increment if we fail to claim space
2012-07-23 4:18 ` Theodore Ts'o
@ 2012-07-23 15:46 ` Brian Foster
0 siblings, 0 replies; 3+ messages in thread
From: Brian Foster @ 2012-07-23 15:46 UTC (permalink / raw)
To: Theodore Ts'o; +Cc: linux-ext4
On 07/23/2012 12:18 AM, Theodore Ts'o wrote:
> On Mon, Apr 02, 2012 at 11:14:20AM -0400, Brian Foster wrote:
>> From: Brian Foster <bfoster@redhat.com>
>>
>> If we call ext4_calc_metadata_amount() and then fail to claim
>> the space, a subsequent successful request to a block covered
>> by the same ext2 indirect block will set md_needed to 0, fail
>> to update the associated counters and result in a delayed md
>> block allocation without a reservation. Decrement
>> i_da_metadata_calc_len on failure to ensure the next
>> reservation sets md_needed correctly.
>>
>> Signed-off-by: Brian Foster <bfoster@redhat.com>
>
> Hi Brian,
>
> This patch was not quite right. i_data_metadata_calc_len is not the
> only side effect of ext4_calc_metadata(). We need to undo the side
> effects not only when exit with an error, but also if we yield and
> then retry the claim. Also, in the extent case we don't always modify
> i_data_metadata_calc_len, so just decrementing isn't necessarily going
> to do the right thing.
>
> So this is the patch which I am testing....
>
Hi Ted,
Ok, your patch makes sense. Thanks for the explanation. FWIW, I ran it
through my reproducer a couple times and it passes.
Brian
> - Ted
>
> commit 19ec0f1fe139a642f688177ffd2f91a1c09f6bc0
> Author: Theodore Ts'o <tytso@mit.edu>
> Date: Mon Jul 23 00:00:20 2012 -0400
>
> ext4: undo ext4_calc_metadata_amount if we fail to claim space
>
> The function ext4_calc_metadata_amount() has side effects, although
> it's not obvious from its function name. So if we fail to claim
> space, regardless of whether we retry to claim the space again, or
> return an error, we need to undo these side effects.
>
> Otherwise we can end up incorrectly calculating the number of metadata
> blocks needed for the operation, which was responsible for an xfstests
> failure for test #271 when using an ext2 file system with delalloc
> enabled.
>
> Reported-by: Brian Foster <bfoster@redhat.com>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> Cc: stable@vger.kernel.org
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 25f809d..89b59cb 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1182,6 +1182,17 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
> struct ext4_inode_info *ei = EXT4_I(inode);
> unsigned int md_needed;
> int ret;
> + ext4_lblk_t save_last_lblock;
> + int save_len;
> +
> + /*
> + * We will charge metadata quota at writeout time; this saves
> + * us from metadata over-estimation, though we may go over by
> + * a small amount in the end. Here we just reserve for data.
> + */
> + ret = dquot_reserve_block(inode, EXT4_C2B(sbi, 1));
> + if (ret)
> + return ret;
>
> /*
> * recalculate the amount of metadata blocks to reserve
> @@ -1190,32 +1201,31 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
> */
> repeat:
> spin_lock(&ei->i_block_reservation_lock);
> + /*
> + * ext4_calc_metadata_amount() has side effects, which we have
> + * to be prepared undo if we fail to claim space.
> + */
> + save_len = ei->i_da_metadata_calc_len;
> + save_last_lblock = ei->i_da_metadata_calc_last_lblock;
> md_needed = EXT4_NUM_B2C(sbi,
> ext4_calc_metadata_amount(inode, lblock));
> trace_ext4_da_reserve_space(inode, md_needed);
> - spin_unlock(&ei->i_block_reservation_lock);
>
> /*
> - * We will charge metadata quota at writeout time; this saves
> - * us from metadata over-estimation, though we may go over by
> - * a small amount in the end. Here we just reserve for data.
> - */
> - ret = dquot_reserve_block(inode, EXT4_C2B(sbi, 1));
> - if (ret)
> - return ret;
> - /*
> * We do still charge estimated metadata to the sb though;
> * we cannot afford to run out of free blocks.
> */
> if (ext4_claim_free_clusters(sbi, md_needed + 1, 0)) {
> - dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
> + ei->i_da_metadata_calc_len = save_len;
> + ei->i_da_metadata_calc_last_lblock = save_last_lblock;
> + spin_unlock(&ei->i_block_reservation_lock);
> if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
> yield();
> goto repeat;
> }
> + dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
> return -ENOSPC;
> }
> - spin_lock(&ei->i_block_reservation_lock);
> ei->i_reserved_data_blocks++;
> ei->i_reserved_meta_blocks += md_needed;
> spin_unlock(&ei->i_block_reservation_lock);
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-04-02 15:14 [RFC PATCH 2/2] ext4: undo ei->i_da_metadata_calc_len increment if we fail to claim space Brian Foster
2012-07-23 4:18 ` Theodore Ts'o
2012-07-23 15:46 ` Brian Foster
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