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Date: Tue, 9 Jul 2019 23:03:43 +0200
From: Jan Kara <jack@...e.cz>
To: " Steven J. Magnani " <steve.magnani@...idescorp.com>
Cc: Jan Kara <jack@...e.com>,
"Steven J . Magnani" <steve@...idescorp.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] udf: Fix incorrect final NOT_ALLOCATED (hole) extent
length
On Sun 30-06-19 21:39:35, Steven J. Magnani wrote:
> In some cases, using the 'truncate' command to extend a UDF file results
> in a mismatch between the length of the file's extents (specifically, due
> to incorrect length of the final NOT_ALLOCATED extent) and the information
> (file) length. The discrepancy can prevent other operating systems
> (i.e., Windows 10) from opening the file.
>
> Two particular errors have been observed when extending a file:
>
> 1. The final extent is larger than it should be, having been rounded up
> to a multiple of the block size.
>
> B. The final extent is not shorter than it should be, due to not having
> been updated when the file's information length was increased.
>
> Change since v1:
> Simplified udf_do_extend_file() API, partially by factoring out its
> handling of the "extending within the last file block" corner case.
>
> Fixes: 2c948b3f86e5 ("udf: Avoid IO in udf_clear_inode")
> Signed-off-by: Steven J. Magnani <steve@...idescorp.com>
Thanks for the patch! I have added it with some small modifications to my
tree. Below are the changes I did.
> --- a/fs/udf/inode.c 2019-05-24 21:17:33.659704533 -0500
> +++ b/fs/udf/inode.c 2019-06-29 21:10:48.938562957 -0500
> @@ -470,13 +470,15 @@ static struct buffer_head *udf_getblk(st
> return NULL;
> }
>
> -/* Extend the file by 'blocks' blocks, return the number of extents added */
> +/* Extend the file with new blocks totaling 'new_block_bytes',
> + * return the number of extents added
> + */
> static int udf_do_extend_file(struct inode *inode,
> struct extent_position *last_pos,
> struct kernel_long_ad *last_ext,
> - sector_t blocks)
> + loff_t new_block_bytes)
> {
> - sector_t add;
> + unsigned long add;
I've changed the type here to uint32_t since that's what we usually use for
extent size.
> +/* Extend the final block of the file to final_block_len bytes */
> +static int udf_do_extend_final_block(struct inode *inode,
Changed return type to void since the function doesn't return anything
useful.
> + struct extent_position *last_pos,
> + struct kernel_long_ad *last_ext,
> + unsigned long final_block_len)
> +{
> + struct super_block *sb = inode->i_sb;
> + struct kernel_lb_addr tmploc;
> + uint32_t tmplen;
> + struct udf_inode_info *iinfo;
> + unsigned long added_bytes;
> +
> + iinfo = UDF_I(inode);
> +
> + added_bytes = final_block_len -
> + (last_ext->extLength & (sb->s_blocksize - 1));
> + last_ext->extLength += added_bytes;
> + iinfo->i_lenExtents += added_bytes;
> +
> + udf_write_aext(inode, last_pos, &last_ext->extLocation,
> + last_ext->extLength, 1);
> + /*
> + * We've rewritten the last extent but there may be empty
> + * indirect extent after it - enter it.
> + */
> + udf_next_aext(inode, last_pos, &tmploc, &tmplen, 0);
> +
> + /* last_pos should point to the last written extent... */
> + if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
> + last_pos->offset -= sizeof(struct short_ad);
> + else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)
> + last_pos->offset -= sizeof(struct long_ad);
> + else
> + return -EIO;
I've dropped the updates of last_pos here. This function is used from a
single place and passed epos isn't used in any way after the function
returns.
> +
> + return 0;
> +}
> +
> static int udf_extend_file(struct inode *inode, loff_t newsize)
> {
>
> @@ -605,10 +643,12 @@ static int udf_extend_file(struct inode
> int8_t etype;
> struct super_block *sb = inode->i_sb;
> sector_t first_block = newsize >> sb->s_blocksize_bits, offset;
> + unsigned long partial_final_block;
Again uint32_t here.
> @@ -643,7 +673,22 @@ static int udf_extend_file(struct inode
> &extent.extLength, 0);
> extent.extLength |= etype << 30;
> }
> - err = udf_do_extend_file(inode, &epos, &extent, offset);
> +
> + partial_final_block = newsize & (sb->s_blocksize - 1);
> +
> + /* File has extent covering the new size (could happen when extending
> + * inside a block)?
> + */
> + if (within_final_block) {
> + /* Extending file within the last file block */
> + err = udf_do_extend_final_block(inode, &epos, &extent,
> + partial_final_block);
> + } else {
> + loff_t add = (offset << sb->s_blocksize_bits) |
Typed 'offset' to loff_t before shifting. Otherwise the shift could
overflow for systems with 32-bit sector_t.
> + partial_final_block;
> + err = udf_do_extend_file(inode, &epos, &extent, add);
> + }
> +
> if (err < 0)
> goto out;
> err = 0;
...
> @@ -760,7 +806,8 @@ static sector_t inode_getblk(struct inod
> startnum = (offset > 0);
> }
> /* Create extents for the hole between EOF and offset */
> - ret = udf_do_extend_file(inode, &prev_epos, laarr, offset);
> + hole_len = offset << inode->i_sb->s_blocksize_bits;
The same as above.
> + ret = udf_do_extend_file(inode, &prev_epos, laarr, hole_len);
> if (ret < 0) {
> *err = ret;
> newblock = 0;
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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