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Date:	Fri, 14 Dec 2012 00:17:41 +0800
From:	Forrest Liu <forrestl@...ology.com>
To:	"Theodore Ts'o" <tytso@....edu>,
	Ashish Sangwan <ashishsangwan2@...il.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	"Synology/Forrest Liu" <forrestl@...ology.com>
Subject: Re: [PATCH] ext4: fix extent tree corruption that incurred by hole
 punch [V2]

Hi Ted,
   Your patch for fallocate is no problem, my mistake. Sorry~

-Forrest

2012/12/14 Forrest Liu <forrestl@...ology.com>:
> @Ashish
>    I have modified the patch with your suggestion, could you help to review.
>
> @Ted
>    I wrote a script to verify this problem.
>    This script needs tst_extents and fallocate executables from e2fsprogs, and
> fallocate needs your patch with bug fix to do hole punch.
>
>    Steps to run the script
> 1) assign variable blkdev to path of block device that filesystem mount on
> 2) cd to mount point
> 3) run script
>
> Thanks,
> Forrest
>
> # verify hole punch bug
> #
> blkdev=/dev/sda1
> file=punch_test
> cmdfile=cmds
> filesize=`expr 1024 \* 1024 \* 1024`
> blksize=`tst_extents -R "stats" $blkdev | grep "Block size" | cut -d
> ':'  -f 2 | tr -d ' '`
> maxlblks=`expr $filesize \/ $blksize`
>
> rm $file
> touch $file
> fallocate -l $filesize $file
> sync
>
> inode=`tst_extents -R "stat ${file}" $blkdev | grep Inode | cut -d ' ' -f 2`
> echo "Inode number: $inode"
>
> # punch every even blocks
> echo "Punch out every even blocks"
> i=0
> while [ "${i}" -lt "${maxlblks}" ]
> do
>         offset=`expr $i \* $blksize`
>         fallocate -p -o $offset -l $blksize $file
>         i=$(($i+2))
> done
>
> # get lblk from root->ns->down
> echo "inode <$inode>" > cmds
> echo "root" >> cmds
> echo "ns" >> cmds
>
> a=`tst_extents -f $cmdfile $blkdev`
> echo "down" >> cmds
> b=`tst_extents -f $cmdfile $blkdev`
>
> # get output form command "down"
> c=${b:${#a}}
> echo "Out put from command \"down\""
> echo $c
>
> a=`echo ${c#*lblk} | cut -d ',' -f 1`
> lblk_low=`echo $a | cut -d '-' -f 1`
> lblk_hi=`echo $a | cut -d '-' -f 3`
>
> echo ""
> echo "Punch out blocks $lblk_hi, ..., $lblk_low"
>
> i=$lblk_hi
> while [ $i -ge $lblk_low ]
> do
>         offset=`expr $i \* $blksize`
>         fallocate -p -o $offset -l $blksize $file
>         i=$(($i-1))
> done
>
> # verify logical start value is correct or not
> echo "inode <$inode>" > cmds
> echo "root" >> cmds
> a=`tst_extents -f $cmdfile $blkdev`
> echo "ns" >> cmds
> b=`tst_extents -f $cmdfile $blkdev`
>
> c=${b:${#a}}
> c=`echo ${c#*lblk} | cut -d ',' -f 1`
> lblk_start0=`echo $c | cut -d '-' -f 1`
>
> echo "down" >> cmds
> c=`tst_extents -f $cmdfile $blkdev`
> c=${c:${#b}}
> c=`echo ${c#*lblk} | cut -d ',' -f 1`
> lblk_start1=`echo $c | cut -d '-' -f 1`
>
> if [ $lblk_start0 -eq $lblk_start1 ]
> then
>         echo "logical start valie is consistency:$lblk_start0,$lblk_start1"
> else
>         echo "logical start valie is not consistency:$lblk_start0,$lblk_start1"
> fi
>
>
>
> diff --git a/contrib/fallocate.c b/contrib/fallocate.c
> index 0e8319f..c1c08e1 100644
> --- a/contrib/fallocate.c
> +++ b/contrib/fallocate.c
> @@ -35,10 +35,11 @@
>
>  // #include <linux/falloc.h>
>  #define FALLOC_FL_KEEP_SIZE    0x01
> +#define FALLOC_FL_PUNCH_HOLE   0x02 /* de-allocates range */
>
>  void usage(void)
>  {
> -       printf("Usage: fallocate [-nt] [-o offset] -l length filename\n");
> +       printf("Usage: fallocate [-npt] [-o offset] -l length filename\n");
>         exit(EXIT_FAILURE);
>  }
>
> @@ -56,6 +57,7 @@ cvtnum(char *s)
>         char            *sp;
>         int             c;
>
> +
>         i = strtoll(s, &sp, 0);
>         if (i == 0 && sp == s)
>                 return -1LL;
> @@ -94,12 +96,18 @@ int main(int argc, char **argv)
>         int     error;
>         int     tflag = 0;
>
> -       while ((opt = getopt(argc, argv, "nl:ot")) != -1) {
> +       while ((opt = getopt(argc, argv, "npl:o:t")) != -1) {
>                 switch(opt) {
>                 case 'n':
>                         /* do not change filesize */
>                         falloc_mode = FALLOC_FL_KEEP_SIZE;
>                         break;
> +               case 'p':
> +                       /* punch mode */
> +                       falloc_mode = (FALLOC_FL_PUNCH_HOLE |
> +                               FALLOC_FL_KEEP_SIZE);
> +                       break;
> +
>                 case 'l':
>                         length = cvtnum(optarg);
>                         break;
>
> 2012/12/13 Forrest Liu <forrestl@...ology.com>:
>> When depth of extent tree is greater than 1, logical start value
>> of interior node didn't updated correctly in ext4_ext_rm_idx.
>>
>> Signed-off-by: Forrest Liu <forrestl@...ology.com>
>> ---
>>  fs/ext4/extents.c |   22 ++++++++++++++++++----
>>  1 file changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index d3dd618..496952e 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -2190,13 +2190,14 @@ errout:
>>   * removes index from the index block.
>>   */
>>  static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
>> -                       struct ext4_ext_path *path)
>> +                       struct ext4_ext_path *path, int depth)
>>  {
>>         int err;
>>         ext4_fsblk_t leaf;
>>
>>         /* free index block */
>> -       path--;
>> +       depth--;
>> +       path = path + depth;
>>         leaf = ext4_idx_pblock(path->p_idx);
>>         if (unlikely(path->p_hdr->eh_entries == 0)) {
>>                 EXT4_ERROR_INODE(inode, "path->p_hdr->eh_entries == 0");
>> @@ -2221,6 +2222,19 @@ static int ext4_ext_rm_idx(handle_t *handle,
>> struct inode *inode,
>>
>>         ext4_free_blocks(handle, inode, NULL, leaf, 1,
>>                          EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
>> +
>> +       while (--depth >= 0) {
>> +               if (path->p_idx != EXT_FIRST_INDEX(path->p_hdr))
>> +                       break;
>> +               path--;
>> +               err = ext4_ext_get_access(handle, inode, path);
>> +               if (err)
>> +                       break;
>> +               path->p_idx->ei_block = (path+1)->p_idx->ei_block;
>> +               err = ext4_ext_dirty(handle, inode, path);
>> +               if (err)
>> +                       break;
>> +       }
>>         return err;
>>  }
>>
>> @@ -2557,7 +2571,7 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
>>         /* if this leaf is free, then we should
>>          * remove it from index block above */
>>         if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL)
>> -               err = ext4_ext_rm_idx(handle, inode, path + depth);
>> +               err = ext4_ext_rm_idx(handle, inode, path, depth);
>>
>>  out:
>>         return err;
>> @@ -2760,7 +2774,7 @@ again:
>>                                 /* index is empty, remove it;
>>                                  * handle must be already prepared by the
>>                                  * truncatei_leaf() */
>> -                               err = ext4_ext_rm_idx(handle, inode, path + i);
>> +                               err = ext4_ext_rm_idx(handle, inode, path, i);
>>                         }
>>                         /* root level has p_bh == NULL, brelse() eats this */
>>                         brelse(path[i].p_bh);
>> --
>> 1.7.9.5
--
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