[PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[Namjae Jeon]

From: Namjae Jeon <namjae.jeon@samsung.com>

Make the fibmap call the return the proper physical block number for any
offset request in the fallocated range.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
---
 fs/fat/cache.c |   13 ++++++++++---
 fs/fat/fat.h   |    3 +++
 fs/fat/inode.c |    3 +++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index a132666..d22c1a2 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -325,19 +325,26 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
 
 	last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
 	if (sector >= last_block) {
-		if (!create)
-			return 0;
-
 		/*
 		 * Both ->mmu_private and ->i_disksize can access
 		 * on only allocation path. (caller must hold ->i_mutex)
 		 */
 		last_block = (MSDOS_I(inode)->i_disksize + (blocksize - 1))
 			>> blocksize_bits;
+		if (!create) {
+			/* Map a block in fallocated region */
+			if (atomic_read(&MSDOS_I(inode)->beyond_isize))
+				if (sector < last_block)
+					goto out_map_cluster;
+
+			return 0;
+		}
+
 		if (sector >= last_block)
 			return 0;
 	}
 
+out_map_cluster:
 	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
 	offset  = sector & (sbi->sec_per_clus - 1);
 	cluster = fat_bmap_cluster(inode, cluster);
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 7b5851f..b884276 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -129,6 +129,9 @@ struct msdos_inode_info {
 	struct hlist_node i_dir_hash;	/* hash by i_logstart */
 	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
 	struct inode vfs_inode;
+
+	/* for getting block number beyond file size in case of fallocate */
+	atomic_t beyond_isize;
 };
 
 struct fat_slot_info {
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 3636617..1c3192b 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -256,7 +256,10 @@ static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
 
 	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
 	down_read(&MSDOS_I(mapping->host)->truncate_lock);
+	/* To get block number beyond file size in fallocated region */
+	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
 	blocknr = generic_block_bmap(mapping, block, fat_get_block);
+	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
 	up_read(&MSDOS_I(mapping->host)->truncate_lock);
 
 	return blocknr;
-- 
1.7.9.5

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[OGAWA Hirofumi]

Namjae Jeon <linkinjeon@gmail.com> writes:

> From: Namjae Jeon <namjae.jeon@samsung.com>
>
> Make the fibmap call the return the proper physical block number for any
> offset request in the fallocated range.
>
> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
> ---
>  fs/fat/cache.c |   13 ++++++++++---
>  fs/fat/fat.h   |    3 +++
>  fs/fat/inode.c |    3 +++
>  3 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/fs/fat/cache.c b/fs/fat/cache.c
> index a132666..d22c1a2 100644
> --- a/fs/fat/cache.c
> +++ b/fs/fat/cache.c
> @@ -325,19 +325,26 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
>  
>  	last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
>  	if (sector >= last_block) {
> -		if (!create)
> -			return 0;
> -
>  		/*
>  		 * Both ->mmu_private and ->i_disksize can access
>  		 * on only allocation path. (caller must hold ->i_mutex)
>  		 */
>  		last_block = (MSDOS_I(inode)->i_disksize + (blocksize - 1))
>  			>> blocksize_bits;
> +		if (!create) {
> +			/* Map a block in fallocated region */
> +			if (atomic_read(&MSDOS_I(inode)->beyond_isize))
> +				if (sector < last_block)
> +					goto out_map_cluster;
> +
> +			return 0;
> +		}
> +
>  		if (sector >= last_block)
>  			return 0;
>  	}
>  
> +out_map_cluster:
>  	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
>  	offset  = sector & (sbi->sec_per_clus - 1);
>  	cluster = fat_bmap_cluster(inode, cluster);
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index 7b5851f..b884276 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -129,6 +129,9 @@ struct msdos_inode_info {
>  	struct hlist_node i_dir_hash;	/* hash by i_logstart */
>  	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
>  	struct inode vfs_inode;
> +
> +	/* for getting block number beyond file size in case of fallocate */
> +	atomic_t beyond_isize;
>  };
>  
>  struct fat_slot_info {
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index 3636617..1c3192b 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -256,7 +256,10 @@ static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
>  
>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
> +	/* To get block number beyond file size in fallocated region */
> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);

This is racy. While user is using bmap, kernel can allocate new blocks.
We should use another function for this.

For example, something like

fat_get_block_bmap()
{
        [...]
	fat_get_block2(inode, iblock, &max_blocks, bh_result, create, bmap);
        [...]
}

blocknr = generic_block_bmap(mapping, block, fat_get_block_bmap);
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[Namjae Jeon]

2014-02-03, OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:
> Namjae Jeon <linkinjeon@gmail.com> writes:
>
>> From: Namjae Jeon <namjae.jeon@samsung.com>
>>
>> Make the fibmap call the return the proper physical block number for any
>> offset request in the fallocated range.
>>
>> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
>> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
>> ---
>>  fs/fat/cache.c |   13 ++++++++++---
>>  fs/fat/fat.h   |    3 +++
>>  fs/fat/inode.c |    3 +++
>>  3 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/fat/cache.c b/fs/fat/cache.c
>> index a132666..d22c1a2 100644
>> --- a/fs/fat/cache.c
>> +++ b/fs/fat/cache.c
>> @@ -325,19 +325,26 @@ int fat_bmap(struct inode *inode, sector_t sector,
>> sector_t *phys,
>>
>>  	last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
>>  	if (sector >= last_block) {
>> -		if (!create)
>> -			return 0;
>> -
>>  		/*
>>  		 * Both ->mmu_private and ->i_disksize can access
>>  		 * on only allocation path. (caller must hold ->i_mutex)
>>  		 */
>>  		last_block = (MSDOS_I(inode)->i_disksize + (blocksize - 1))
>>  			>> blocksize_bits;
>> +		if (!create) {
>> +			/* Map a block in fallocated region */
>> +			if (atomic_read(&MSDOS_I(inode)->beyond_isize))
>> +				if (sector < last_block)
>> +					goto out_map_cluster;
>> +
>> +			return 0;
>> +		}
>> +
>>  		if (sector >= last_block)
>>  			return 0;
>>  	}
>>
>> +out_map_cluster:
>>  	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
>>  	offset  = sector & (sbi->sec_per_clus - 1);
>>  	cluster = fat_bmap_cluster(inode, cluster);
>> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
>> index 7b5851f..b884276 100644
>> --- a/fs/fat/fat.h
>> +++ b/fs/fat/fat.h
>> @@ -129,6 +129,9 @@ struct msdos_inode_info {
>>  	struct hlist_node i_dir_hash;	/* hash by i_logstart */
>>  	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
>>  	struct inode vfs_inode;
>> +
>> +	/* for getting block number beyond file size in case of fallocate */
>> +	atomic_t beyond_isize;
>>  };
>>
>>  struct fat_slot_info {
>> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
>> index 3636617..1c3192b 100644
>> --- a/fs/fat/inode.c
>> +++ b/fs/fat/inode.c
>> @@ -256,7 +256,10 @@ static sector_t _fat_bmap(struct address_space
>> *mapping, sector_t block)
>>
>>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
>>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
>> +	/* To get block number beyond file size in fallocated region */
>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);
>
> This is racy. While user is using bmap, kernel can allocate new blocks.
> We should use another function for this.
I understand that fat can map fallocated blocks in read case while
user is using bmap.
But I can not find the case allocate new blocks.
If I am missing something, Could you please elaborate more ?
Is it a case of _bmap request returning the block number for block
allocated in parallel write path ?

Thanks.
>
> For example, something like
>
> fat_get_block_bmap()
> {
>         [...]
> 	fat_get_block2(inode, iblock, &max_blocks, bh_result, create, bmap);
>         [...]
> }
>
> blocknr = generic_block_bmap(mapping, block, fat_get_block_bmap);
> --
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[OGAWA Hirofumi]

Namjae Jeon <linkinjeon@gmail.com> writes:

>>>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
>>>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
>>> +	/* To get block number beyond file size in fallocated region */
>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>>>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>>>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);
>>
>> This is racy. While user is using bmap, kernel can allocate new blocks.
>> We should use another function for this.
> I understand that fat can map fallocated blocks in read case while
> user is using bmap.
> But I can not find the case allocate new blocks.
> If I am missing something, Could you please elaborate more ?
> Is it a case of _bmap request returning the block number for block
> allocated in parallel write path ?

->beyond_size is global for inode. So, write(2) path on same inode with
bmap() also can see 1 set by bmap() while another process is using bmap().
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[Namjae Jeon]

2014-02-04, OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:
> Namjae Jeon <linkinjeon@gmail.com> writes:
>
>>>>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated.
>>>> */
>>>>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>> +	/* To get block number beyond file size in fallocated region */
>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>>>>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>>>>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>
>>> This is racy. While user is using bmap, kernel can allocate new blocks.
>>> We should use another function for this.
>> I understand that fat can map fallocated blocks in read case while
>> user is using bmap.
>> But I can not find the case allocate new blocks.
>> If I am missing something, Could you please elaborate more ?
>> Is it a case of _bmap request returning the block number for block
>> allocated in parallel write path ?
>
> ->beyond_size is global for inode. So, write(2) path on same inode with
> bmap() also can see 1 set by bmap() while another process is using bmap().
'create' flag  will be 1 in write(2) path. ->beyond_isize will only be
checked when 'create' flag is 0. Is there any case to be racy by
beyond_isize in write(2) path ?

Thanks.
> --
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[OGAWA Hirofumi]

Namjae Jeon <linkinjeon@gmail.com> writes:

> 2014-02-04, OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:
>> Namjae Jeon <linkinjeon@gmail.com> writes:
>>
>>>>>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated.
>>>>> */
>>>>>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>>> +	/* To get block number beyond file size in fallocated region */
>>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>>>>>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
>>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>>>>>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>>
>>>> This is racy. While user is using bmap, kernel can allocate new blocks.
>>>> We should use another function for this.
>>> I understand that fat can map fallocated blocks in read case while
>>> user is using bmap.
>>> But I can not find the case allocate new blocks.
>>> If I am missing something, Could you please elaborate more ?
>>> Is it a case of _bmap request returning the block number for block
>>> allocated in parallel write path ?
>>
>> ->beyond_size is global for inode. So, write(2) path on same inode with
>> bmap() also can see 1 set by bmap() while another process is using bmap().
> 'create' flag  will be 1 in write(2) path. ->beyond_isize will only be
> checked when 'create' flag is 0. Is there any case to be racy by
> beyond_isize in write(2) path ?

Ah, so instead of write, it will assign physical address to buffers
beyond i_size for simple read if race?  In this case, it is still wrong.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

[Namjae Jeon]

2014-02-04, OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:
> Namjae Jeon <linkinjeon@gmail.com> writes:
>
>> 2014-02-04, OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:
>>> Namjae Jeon <linkinjeon@gmail.com> writes:
>>>
>>>>>>  	/* fat_get_cluster() assumes the requested blocknr isn't truncated.
>>>>>> */
>>>>>>  	down_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>>>> +	/* To get block number beyond file size in fallocated region */
>>>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
>>>>>>  	blocknr = generic_block_bmap(mapping, block, fat_get_block);
>>>>>> +	atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
>>>>>>  	up_read(&MSDOS_I(mapping->host)->truncate_lock);
>>>>>
>>>>> This is racy. While user is using bmap, kernel can allocate new
>>>>> blocks.
>>>>> We should use another function for this.
>>>> I understand that fat can map fallocated blocks in read case while
>>>> user is using bmap.
>>>> But I can not find the case allocate new blocks.
>>>> If I am missing something, Could you please elaborate more ?
>>>> Is it a case of _bmap request returning the block number for block
>>>> allocated in parallel write path ?
>>>
>>> ->beyond_size is global for inode. So, write(2) path on same inode with
>>> bmap() also can see 1 set by bmap() while another process is using
>>> bmap().
>> 'create' flag  will be 1 in write(2) path. ->beyond_isize will only be
>> checked when 'create' flag is 0. Is there any case to be racy by
>> beyond_isize in write(2) path ?
>
> Ah, so instead of write, it will assign physical address to buffers
> beyond i_size for simple read if race?  In this case, it is still wrong.
Right. I will fix this case.
Thanks for review!
> --
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>