Hi,
> From: Leonard Michlmayr<leonard.michlmayr@xxxxxxxxx>
>
> ext4_fiemap() rounds the length of the requested range down to
> blocksize, which is is not the true number of blocks that cover the
> requested region. This problem is especially impressive if the user
> requests only the first byte of a file: not a single extent will be
> reported.
<snip>
> start_blk = start>> inode->i_sb->s_blocksize_bits;
> - len_blks = len>> inode->i_sb->s_blocksize_bits;
> + last_blk = (start + len - 1)>> inode->i_sb->s_blocksize_bits;
> + len_blks = last_blk - start_blk + 1;
In 1KB block size, the overflow occurs at above line.
Since last_blk is set 0xffffffff when len is equal to s_maxbytes.
Therefore ext4_fiemap() can not get correct extent information
with 0 length. How about adding this change?
Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
---
extents.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- linux-2.6.33-rc8-a/fs/ext4/extents.c 2010-03-03 14:53:49.000000000 +0900
+++ linux-2.6.33-rc8-b/fs/ext4/extents.c 2010-03-03 15:31:57.000000000 +0900
@@ -3912,7 +3912,8 @@ int ext4_fiemap(struct inode *inode, str
start_blk = start >> inode->i_sb->s_blocksize_bits;
last_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
- len_blks = last_blk - start_blk + 1;
+ len_blks = (loff_t)last_blk - start_blk + 1 < EXT_MAX_BLOCK ?
+ last_blk - start_blk + 1 : EXT_MAX_BLOCK;
/*
* Walk the extent tree gathering extent information.
(2010/03/03 3:18), Theodore Ts'o wrote:
From: Leonard Michlmayr<leonard.michlmayr@xxxxxxxxx>
ext4_fiemap() rounds the length of the requested range down to
blocksize, which is is not the true number of blocks that cover the
requested region. This problem is especially impressive if the user
requests only the first byte of a file: not a single extent will be
reported.
We fix this by calculating the last block of the region and then
subtract to find the number of blocks in the extents.
Signed-off-by: Leonard Michlmayr<leonard.michlmayr@xxxxxxxxx>
Signed-off-by: "Theodore Ts'o"<tytso@xxxxxxx>
---
fs/ext4/extents.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bd80891..bc9860f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3768,7 +3768,6 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len)
{
ext4_lblk_t start_blk;
- ext4_lblk_t len_blks;
int error = 0;
/* fallback to generic here if not in extents fmt */
@@ -3782,8 +3781,11 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
if (fieinfo->fi_flags& FIEMAP_FLAG_XATTR) {
error = ext4_xattr_fiemap(inode, fieinfo);
} else {
+ ext4_lblk_t last_blk, len_blks;
+
start_blk = start>> inode->i_sb->s_blocksize_bits;
- len_blks = len>> inode->i_sb->s_blocksize_bits;
+ last_blk = (start + len - 1)>> inode->i_sb->s_blocksize_bits;
+ len_blks = last_blk - start_blk + 1;
/*
* Walk the extent tree gathering extent information.
--
Akira Fujita <a-fujita@xxxxxxxxxxxxx>
The First Fundamental Software Development Group,
Software Development Division,
NEC Software Tohoku, Ltd.
--Separator@a-fujita@rs.jp.nec.com:
--
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