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ext4: fix ext4_ext_fiemap_cb() to handle blocks before request range correctly 

To get delayed-extent information, ext4_ext_fiemap_cb() looks up
pagecache, it thus collects information starting from a page's
head block.

If blocksize < pagesize, the beginning blocks of a page may lies
before the request range. So ext4_ext_fiemap_cb() should proceed
ignoring them, because they has been handled before. If no mapped
buffer in the range is found in the 1st page, we need to look up
the 2nd page, otherwise delayed-extents after a hole will be ignored.

Without this patch, xfstests 225 will hung on ext4 with 1K block.

Reported-by: Amir Goldstein <amir73il@users.sourceforge.net>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Yongqiang Yang 2011-05-24 11:36:58 -04:00 committed by Theodore Ts'o
parent 072bd7ea74
commit b221349fa8
1 changed files with 35 additions and 14 deletions
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49
fs/ext4/extents.c
View File

@ -3688,6 +3688,7 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
pgoff_t last_offset;
pgoff_t offset;
pgoff_t index;
pgoff_t start_index = 0;
struct page **pages = NULL;
struct buffer_head *bh = NULL;
struct buffer_head *head = NULL;
@ -3714,39 +3715,57 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
kfree(pages);
return EXT_CONTINUE;
}
index = 0;
next_page:
/* Try to find the 1st mapped buffer. */
end = ((__u64)pages[0]->index << PAGE_SHIFT) >>
end = ((__u64)pages[index]->index << PAGE_SHIFT) >>
blksize_bits;
if (!page_has_buffers(pages[0]))
if (!page_has_buffers(pages[index]))
goto out;
head = page_buffers(pages[0]);
head = page_buffers(pages[index]);
if (!head)
goto out;
index++;
bh = head;
do {
if (buffer_mapped(bh)) {
if (end >= newex->ec_block +
newex->ec_len)
/* The buffer is out of
* the request range.
*/
goto out;
if (buffer_mapped(bh) &&
end >= newex->ec_block) {
start_index = index - 1;
/* get the 1st mapped buffer. */
if (end > newex->ec_block +
newex->ec_len)
/* The buffer is out of
* the request range.
*/
goto out;
goto found_mapped_buffer;
}
bh = bh->b_this_page;
end++;
} while (bh != head);
/* No mapped buffer found. */
goto out;
/* No mapped buffer in the range found in this page,
* We need to look up next page.
*/
if (index >= ret) {
/* There is no page left, but we need to limit
* newex->ec_len.
*/
newex->ec_len = end - newex->ec_block;
goto out;
}
goto next_page;
} else {
/*Find contiguous delayed buffers. */
if (ret > 0 && pages[0]->index == last_offset)
head = page_buffers(pages[0]);
bh = head;
index = 1;
start_index = 0;
}
found_mapped_buffer:
@ -3769,7 +3788,7 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
end++;
} while (bh != head);
for (index = 1; index < ret; index++) {
for (; index < ret; index++) {
if (!page_has_buffers(pages[index])) {
bh = NULL;
break;
@ -3779,8 +3798,10 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
bh = NULL;
break;
}
if (pages[index]->index !=
pages[0]->index + index) {
pages[start_index]->index + index
- start_index) {
/* Blocks are not contiguous. */
bh = NULL;
break;