[PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()

[PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()

[Lukas Czerner]

The overflow might happen when passing blocknr into
ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
which might be smaller than uint64_t. This will most likely happen when
calling FITRIM with the default argument len = ULLONG_MAX.

Fix this by using "end" variable instead of "start+len" as it is easier
to get right and specifically check that the end is not beyond the end
of the file system, so we are sure that the result of
get_group_no_and_offset() will not overflow. Otherwise truncate it to
the size of the file system.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Jan Kara <jack@suse.cz>
---
v2: Squash the 'don't forget to discard last block in a group' into this one
    since this is the commit which reveals the bug.

 fs/ext3/balloc.c |   77 +++++++++++++++++++++++++++--------------------------
 1 files changed, 39 insertions(+), 38 deletions(-)

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index a203892..997da27 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1970,7 +1970,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
 	sbi = EXT3_SB(sb);
 
 	 /* Walk through the whole group */
-	while (start < max) {
+	while (start <= max) {
 		start = bitmap_search_next_usable_block(start, bitmap_bh, max);
 		if (start < 0)
 			break;
@@ -1980,7 +1980,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
 		 * Allocate contiguous free extents by setting bits in the
 		 * block bitmap
 		 */
-		while (next < max
+		while (next <= max
 			&& claim_block(sb_bgl_lock(sbi, group),
 					next, bitmap_bh)) {
 			next++;
@@ -2091,73 +2091,74 @@ err_out:
  */
 int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
 {
-	ext3_grpblk_t last_block, first_block, free_blocks;
-	unsigned long first_group, last_group;
-	unsigned long group, ngroups;
+	ext3_grpblk_t last_block, first_block;
+	unsigned long group, first_group, last_group;
 	struct ext3_group_desc *gdp;
 	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
-	uint64_t start, len, minlen, trimmed;
+	uint64_t start, minlen, end, trimmed = 0;
+	ext3_fsblk_t first_data_blk =
+			le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
 	ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
 	int ret = 0;
 
-	start = (range->start >> sb->s_blocksize_bits) +
-		le32_to_cpu(es->s_first_data_block);
-	len = range->len >> sb->s_blocksize_bits;
+	start = range->start >> sb->s_blocksize_bits;
+	end = start + (range->len >> sb->s_blocksize_bits) - 1;
 	minlen = range->minlen >> sb->s_blocksize_bits;
-	trimmed = 0;
 
-	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
+	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
+	    unlikely(start >= max_blks))
 		return -EINVAL;
-	if (start >= max_blks)
-		return -EINVAL;
-	if (start + len > max_blks)
-		len = max_blks - start;
+	if (end >= max_blks)
+		end = max_blks - 1;
+	if (end <= first_data_blk)
+		goto out;
+	if (start < first_data_blk)
+		start = first_data_blk;
 
-	ngroups = EXT3_SB(sb)->s_groups_count;
 	smp_rmb();
 
 	/* Determine first and last group to examine based on start and len */
 	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
 				     &first_group, &first_block);
-	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
+	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
 				     &last_group, &last_block);
-	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
-	last_block = EXT3_BLOCKS_PER_GROUP(sb);
 
-	if (first_group > last_group)
-		return -EINVAL;
+	/* end now represents the last block to discard in this group */
+	end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
 
 	for (group = first_group; group <= last_group; group++) {
 		gdp = ext3_get_group_desc(sb, group, NULL);
 		if (!gdp)
 			break;
 
-		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
-		if (free_blocks < minlen)
-			continue;
-
 		/*
 		 * For all the groups except the last one, last block will
-		 * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
-		 * change it for the last group in which case first_block +
-		 * len < EXT3_BLOCKS_PER_GROUP(sb).
+		 * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
+		 * change it for the last group, note that last_block is
+		 * already computed earlier by ext3_get_group_no_and_offset()
 		 */
-		if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
-			last_block = first_block + len;
-		len -= last_block - first_block;
+		if (group == last_group)
+			end = last_block;
 
-		ret = ext3_trim_all_free(sb, group, first_block,
-					last_block, minlen);
-		if (ret < 0)
-			break;
+		if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
+			ret = ext3_trim_all_free(sb, group, first_block,
+						 end, minlen);
+			if (ret < 0)
+				break;
+			trimmed += ret;
+		}
 
-		trimmed += ret;
+		/*
+		 * For every group except the first one, we are sure
+		 * that the first block to discard will be block #0.
+		 */
 		first_block = 0;
 	}
 
-	if (ret >= 0)
+	if (ret > 0)
 		ret = 0;
-	range->len = trimmed * sb->s_blocksize;
 
+out:
+	range->len = trimmed * sb->s_blocksize;
 	return ret;
 }
-- 
1.7.4.4

Re: [PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()

[Lukas Czerner]

On Fri, 2 Mar 2012, Lukas Czerner wrote:

> The overflow might happen when passing blocknr into
> ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
> which might be smaller than uint64_t. This will most likely happen when
> calling FITRIM with the default argument len = ULLONG_MAX.
> 
> Fix this by using "end" variable instead of "start+len" as it is easier
> to get right and specifically check that the end is not beyond the end
> of the file system, so we are sure that the result of
> get_group_no_and_offset() will not overflow. Otherwise truncate it to
> the size of the file system.

ping

> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> ---
> v2: Squash the 'don't forget to discard last block in a group' into this one
>     since this is the commit which reveals the bug.
> 
>  fs/ext3/balloc.c |   77 +++++++++++++++++++++++++++--------------------------
>  1 files changed, 39 insertions(+), 38 deletions(-)
> 
> diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> index a203892..997da27 100644
> --- a/fs/ext3/balloc.c
> +++ b/fs/ext3/balloc.c
> @@ -1970,7 +1970,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
>  	sbi = EXT3_SB(sb);
>  
>  	 /* Walk through the whole group */
> -	while (start < max) {
> +	while (start <= max) {
>  		start = bitmap_search_next_usable_block(start, bitmap_bh, max);
>  		if (start < 0)
>  			break;
> @@ -1980,7 +1980,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
>  		 * Allocate contiguous free extents by setting bits in the
>  		 * block bitmap
>  		 */
> -		while (next < max
> +		while (next <= max
>  			&& claim_block(sb_bgl_lock(sbi, group),
>  					next, bitmap_bh)) {
>  			next++;
> @@ -2091,73 +2091,74 @@ err_out:
>   */
>  int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
>  {
> -	ext3_grpblk_t last_block, first_block, free_blocks;
> -	unsigned long first_group, last_group;
> -	unsigned long group, ngroups;
> +	ext3_grpblk_t last_block, first_block;
> +	unsigned long group, first_group, last_group;
>  	struct ext3_group_desc *gdp;
>  	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
> -	uint64_t start, len, minlen, trimmed;
> +	uint64_t start, minlen, end, trimmed = 0;
> +	ext3_fsblk_t first_data_blk =
> +			le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
>  	ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
>  	int ret = 0;
>  
> -	start = (range->start >> sb->s_blocksize_bits) +
> -		le32_to_cpu(es->s_first_data_block);
> -	len = range->len >> sb->s_blocksize_bits;
> +	start = range->start >> sb->s_blocksize_bits;
> +	end = start + (range->len >> sb->s_blocksize_bits) - 1;
>  	minlen = range->minlen >> sb->s_blocksize_bits;
> -	trimmed = 0;
>  
> -	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
> +	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
> +	    unlikely(start >= max_blks))
>  		return -EINVAL;
> -	if (start >= max_blks)
> -		return -EINVAL;
> -	if (start + len > max_blks)
> -		len = max_blks - start;
> +	if (end >= max_blks)
> +		end = max_blks - 1;
> +	if (end <= first_data_blk)
> +		goto out;
> +	if (start < first_data_blk)
> +		start = first_data_blk;
>  
> -	ngroups = EXT3_SB(sb)->s_groups_count;
>  	smp_rmb();
>  
>  	/* Determine first and last group to examine based on start and len */
>  	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
>  				     &first_group, &first_block);
> -	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
> +	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
>  				     &last_group, &last_block);
> -	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
> -	last_block = EXT3_BLOCKS_PER_GROUP(sb);
>  
> -	if (first_group > last_group)
> -		return -EINVAL;
> +	/* end now represents the last block to discard in this group */
> +	end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
>  
>  	for (group = first_group; group <= last_group; group++) {
>  		gdp = ext3_get_group_desc(sb, group, NULL);
>  		if (!gdp)
>  			break;
>  
> -		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> -		if (free_blocks < minlen)
> -			continue;
> -
>  		/*
>  		 * For all the groups except the last one, last block will
> -		 * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
> -		 * change it for the last group in which case first_block +
> -		 * len < EXT3_BLOCKS_PER_GROUP(sb).
> +		 * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
> +		 * change it for the last group, note that last_block is
> +		 * already computed earlier by ext3_get_group_no_and_offset()
>  		 */
> -		if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
> -			last_block = first_block + len;
> -		len -= last_block - first_block;
> +		if (group == last_group)
> +			end = last_block;
>  
> -		ret = ext3_trim_all_free(sb, group, first_block,
> -					last_block, minlen);
> -		if (ret < 0)
> -			break;
> +		if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
> +			ret = ext3_trim_all_free(sb, group, first_block,
> +						 end, minlen);
> +			if (ret < 0)
> +				break;
> +			trimmed += ret;
> +		}
>  
> -		trimmed += ret;
> +		/*
> +		 * For every group except the first one, we are sure
> +		 * that the first block to discard will be block #0.
> +		 */
>  		first_block = 0;
>  	}
>  
> -	if (ret >= 0)
> +	if (ret > 0)
>  		ret = 0;
> -	range->len = trimmed * sb->s_blocksize;
>  
> +out:
> +	range->len = trimmed * sb->s_blocksize;
>  	return ret;
>  }
> 

-- 

Re: [PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()

[Jan Kara]

On Wed 21-03-12 13:54:12, Lukas Czerner wrote:
> On Fri, 2 Mar 2012, Lukas Czerner wrote:
> 
> > The overflow might happen when passing blocknr into
> > ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
> > which might be smaller than uint64_t. This will most likely happen when
> > calling FITRIM with the default argument len = ULLONG_MAX.
> > 
> > Fix this by using "end" variable instead of "start+len" as it is easier
> > to get right and specifically check that the end is not beyond the end
> > of the file system, so we are sure that the result of
> > get_group_no_and_offset() will not overflow. Otherwise truncate it to
> > the size of the file system.
> 
> ping
  Hmm, maybe I forgot to send email but the patch is in my for_next branch
and I'll send it to Linus in this merge window.

								Honza

> > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> > Cc: Jan Kara <jack@suse.cz>
> > ---
> > v2: Squash the 'don't forget to discard last block in a group' into this one
> >     since this is the commit which reveals the bug.
> > 
> >  fs/ext3/balloc.c |   77 +++++++++++++++++++++++++++--------------------------
> >  1 files changed, 39 insertions(+), 38 deletions(-)
> > 
> > diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> > index a203892..997da27 100644
> > --- a/fs/ext3/balloc.c
> > +++ b/fs/ext3/balloc.c
> > @@ -1970,7 +1970,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
> >  	sbi = EXT3_SB(sb);
> >  
> >  	 /* Walk through the whole group */
> > -	while (start < max) {
> > +	while (start <= max) {
> >  		start = bitmap_search_next_usable_block(start, bitmap_bh, max);
> >  		if (start < 0)
> >  			break;
> > @@ -1980,7 +1980,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
> >  		 * Allocate contiguous free extents by setting bits in the
> >  		 * block bitmap
> >  		 */
> > -		while (next < max
> > +		while (next <= max
> >  			&& claim_block(sb_bgl_lock(sbi, group),
> >  					next, bitmap_bh)) {
> >  			next++;
> > @@ -2091,73 +2091,74 @@ err_out:
> >   */
> >  int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
> >  {
> > -	ext3_grpblk_t last_block, first_block, free_blocks;
> > -	unsigned long first_group, last_group;
> > -	unsigned long group, ngroups;
> > +	ext3_grpblk_t last_block, first_block;
> > +	unsigned long group, first_group, last_group;
> >  	struct ext3_group_desc *gdp;
> >  	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
> > -	uint64_t start, len, minlen, trimmed;
> > +	uint64_t start, minlen, end, trimmed = 0;
> > +	ext3_fsblk_t first_data_blk =
> > +			le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
> >  	ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
> >  	int ret = 0;
> >  
> > -	start = (range->start >> sb->s_blocksize_bits) +
> > -		le32_to_cpu(es->s_first_data_block);
> > -	len = range->len >> sb->s_blocksize_bits;
> > +	start = range->start >> sb->s_blocksize_bits;
> > +	end = start + (range->len >> sb->s_blocksize_bits) - 1;
> >  	minlen = range->minlen >> sb->s_blocksize_bits;
> > -	trimmed = 0;
> >  
> > -	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
> > +	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
> > +	    unlikely(start >= max_blks))
> >  		return -EINVAL;
> > -	if (start >= max_blks)
> > -		return -EINVAL;
> > -	if (start + len > max_blks)
> > -		len = max_blks - start;
> > +	if (end >= max_blks)
> > +		end = max_blks - 1;
> > +	if (end <= first_data_blk)
> > +		goto out;
> > +	if (start < first_data_blk)
> > +		start = first_data_blk;
> >  
> > -	ngroups = EXT3_SB(sb)->s_groups_count;
> >  	smp_rmb();
> >  
> >  	/* Determine first and last group to examine based on start and len */
> >  	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
> >  				     &first_group, &first_block);
> > -	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
> > +	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
> >  				     &last_group, &last_block);
> > -	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
> > -	last_block = EXT3_BLOCKS_PER_GROUP(sb);
> >  
> > -	if (first_group > last_group)
> > -		return -EINVAL;
> > +	/* end now represents the last block to discard in this group */
> > +	end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
> >  
> >  	for (group = first_group; group <= last_group; group++) {
> >  		gdp = ext3_get_group_desc(sb, group, NULL);
> >  		if (!gdp)
> >  			break;
> >  
> > -		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> > -		if (free_blocks < minlen)
> > -			continue;
> > -
> >  		/*
> >  		 * For all the groups except the last one, last block will
> > -		 * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
> > -		 * change it for the last group in which case first_block +
> > -		 * len < EXT3_BLOCKS_PER_GROUP(sb).
> > +		 * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
> > +		 * change it for the last group, note that last_block is
> > +		 * already computed earlier by ext3_get_group_no_and_offset()
> >  		 */
> > -		if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
> > -			last_block = first_block + len;
> > -		len -= last_block - first_block;
> > +		if (group == last_group)
> > +			end = last_block;
> >  
> > -		ret = ext3_trim_all_free(sb, group, first_block,
> > -					last_block, minlen);
> > -		if (ret < 0)
> > -			break;
> > +		if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
> > +			ret = ext3_trim_all_free(sb, group, first_block,
> > +						 end, minlen);
> > +			if (ret < 0)
> > +				break;
> > +			trimmed += ret;
> > +		}
> >  
> > -		trimmed += ret;
> > +		/*
> > +		 * For every group except the first one, we are sure
> > +		 * that the first block to discard will be block #0.
> > +		 */
> >  		first_block = 0;
> >  	}
> >  
> > -	if (ret >= 0)
> > +	if (ret > 0)
> >  		ret = 0;
> > -	range->len = trimmed * sb->s_blocksize;
> >  
> > +out:
> > +	range->len = trimmed * sb->s_blocksize;
> >  	return ret;
> >  }
> > 
> 
> -- 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

Re: [PATCH v2] ext3: fix start and len arguments handling in ext3_trim_fs()

[Lukas Czerner]

On Wed, 21 Mar 2012, Jan Kara wrote:

> On Wed 21-03-12 13:54:12, Lukas Czerner wrote:
> > On Fri, 2 Mar 2012, Lukas Czerner wrote:
> > 
> > > The overflow might happen when passing blocknr into
> > > ext3_get_group_no_and_offset(), because it expects type ext3_fsblk_t
> > > which might be smaller than uint64_t. This will most likely happen when
> > > calling FITRIM with the default argument len = ULLONG_MAX.
> > > 
> > > Fix this by using "end" variable instead of "start+len" as it is easier
> > > to get right and specifically check that the end is not beyond the end
> > > of the file system, so we are sure that the result of
> > > get_group_no_and_offset() will not overflow. Otherwise truncate it to
> > > the size of the file system.
> > 
> > ping
>   Hmm, maybe I forgot to send email but the patch is in my for_next branch
> and I'll send it to Linus in this merge window.
> 
> 								Honza

Thanks Honzo

-Lukas

> 
> > > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> > > Cc: Jan Kara <jack@suse.cz>
> > > ---
> > > v2: Squash the 'don't forget to discard last block in a group' into this one
> > >     since this is the commit which reveals the bug.
> > > 
> > >  fs/ext3/balloc.c |   77 +++++++++++++++++++++++++++--------------------------
> > >  1 files changed, 39 insertions(+), 38 deletions(-)
> > > 
> > > diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> > > index a203892..997da27 100644
> > > --- a/fs/ext3/balloc.c
> > > +++ b/fs/ext3/balloc.c
> > > @@ -1970,7 +1970,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
> > >  	sbi = EXT3_SB(sb);
> > >  
> > >  	 /* Walk through the whole group */
> > > -	while (start < max) {
> > > +	while (start <= max) {
> > >  		start = bitmap_search_next_usable_block(start, bitmap_bh, max);
> > >  		if (start < 0)
> > >  			break;
> > > @@ -1980,7 +1980,7 @@ static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
> > >  		 * Allocate contiguous free extents by setting bits in the
> > >  		 * block bitmap
> > >  		 */
> > > -		while (next < max
> > > +		while (next <= max
> > >  			&& claim_block(sb_bgl_lock(sbi, group),
> > >  					next, bitmap_bh)) {
> > >  			next++;
> > > @@ -2091,73 +2091,74 @@ err_out:
> > >   */
> > >  int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
> > >  {
> > > -	ext3_grpblk_t last_block, first_block, free_blocks;
> > > -	unsigned long first_group, last_group;
> > > -	unsigned long group, ngroups;
> > > +	ext3_grpblk_t last_block, first_block;
> > > +	unsigned long group, first_group, last_group;
> > >  	struct ext3_group_desc *gdp;
> > >  	struct ext3_super_block *es = EXT3_SB(sb)->s_es;
> > > -	uint64_t start, len, minlen, trimmed;
> > > +	uint64_t start, minlen, end, trimmed = 0;
> > > +	ext3_fsblk_t first_data_blk =
> > > +			le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
> > >  	ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
> > >  	int ret = 0;
> > >  
> > > -	start = (range->start >> sb->s_blocksize_bits) +
> > > -		le32_to_cpu(es->s_first_data_block);
> > > -	len = range->len >> sb->s_blocksize_bits;
> > > +	start = range->start >> sb->s_blocksize_bits;
> > > +	end = start + (range->len >> sb->s_blocksize_bits) - 1;
> > >  	minlen = range->minlen >> sb->s_blocksize_bits;
> > > -	trimmed = 0;
> > >  
> > > -	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
> > > +	if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)) ||
> > > +	    unlikely(start >= max_blks))
> > >  		return -EINVAL;
> > > -	if (start >= max_blks)
> > > -		return -EINVAL;
> > > -	if (start + len > max_blks)
> > > -		len = max_blks - start;
> > > +	if (end >= max_blks)
> > > +		end = max_blks - 1;
> > > +	if (end <= first_data_blk)
> > > +		goto out;
> > > +	if (start < first_data_blk)
> > > +		start = first_data_blk;
> > >  
> > > -	ngroups = EXT3_SB(sb)->s_groups_count;
> > >  	smp_rmb();
> > >  
> > >  	/* Determine first and last group to examine based on start and len */
> > >  	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
> > >  				     &first_group, &first_block);
> > > -	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
> > > +	ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
> > >  				     &last_group, &last_block);
> > > -	last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
> > > -	last_block = EXT3_BLOCKS_PER_GROUP(sb);
> > >  
> > > -	if (first_group > last_group)
> > > -		return -EINVAL;
> > > +	/* end now represents the last block to discard in this group */
> > > +	end = EXT3_BLOCKS_PER_GROUP(sb) - 1;
> > >  
> > >  	for (group = first_group; group <= last_group; group++) {
> > >  		gdp = ext3_get_group_desc(sb, group, NULL);
> > >  		if (!gdp)
> > >  			break;
> > >  
> > > -		free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> > > -		if (free_blocks < minlen)
> > > -			continue;
> > > -
> > >  		/*
> > >  		 * For all the groups except the last one, last block will
> > > -		 * always be EXT3_BLOCKS_PER_GROUP(sb), so we only need to
> > > -		 * change it for the last group in which case first_block +
> > > -		 * len < EXT3_BLOCKS_PER_GROUP(sb).
> > > +		 * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
> > > +		 * change it for the last group, note that last_block is
> > > +		 * already computed earlier by ext3_get_group_no_and_offset()
> > >  		 */
> > > -		if (first_block + len < EXT3_BLOCKS_PER_GROUP(sb))
> > > -			last_block = first_block + len;
> > > -		len -= last_block - first_block;
> > > +		if (group == last_group)
> > > +			end = last_block;
> > >  
> > > -		ret = ext3_trim_all_free(sb, group, first_block,
> > > -					last_block, minlen);
> > > -		if (ret < 0)
> > > -			break;
> > > +		if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
> > > +			ret = ext3_trim_all_free(sb, group, first_block,
> > > +						 end, minlen);
> > > +			if (ret < 0)
> > > +				break;
> > > +			trimmed += ret;
> > > +		}
> > >  
> > > -		trimmed += ret;
> > > +		/*
> > > +		 * For every group except the first one, we are sure
> > > +		 * that the first block to discard will be block #0.
> > > +		 */
> > >  		first_block = 0;
> > >  	}
> > >  
> > > -	if (ret >= 0)
> > > +	if (ret > 0)
> > >  		ret = 0;
> > > -	range->len = trimmed * sb->s_blocksize;
> > >  
> > > +out:
> > > +	range->len = trimmed * sb->s_blocksize;
> > >  	return ret;
> > >  }
> > > 
> > 
> > -- 
> > --
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> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

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