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btrfs-progs: map-logical: Rework map-logical logics

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[BUG]
The original map-logical has the following problems:
1) Assert if we pass any tree root bytenr.
The problem is easy to trigger, here the number 29622272 is the bytenr of tree root:

 # btrfs-map-logical -l 29622272 /dev/sda6
 mirror 1 logical 29622272 physical 38010880 device /dev/sda6
 mirror 2 logical 29622272 physical 1111752704 device /dev/sda6
 extent_io.c:582: free_extent_buffer: Assertion `eb->refs < 0` failed.
 btrfs-map-logical[0x41c464]
 btrfs-map-logical(free_extent_buffer+0xc0)[0x41cf10]
 btrfs-map-logical(btrfs_release_all_roots+0x59)[0x40e649]
 btrfs-map-logical(close_ctree+0x1aa)[0x40f51a]
 btrfs-map-logical(main+0x387)[0x4077c7]
 /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7f80a5562790]
 btrfs-map-logical(_start+0x29)[0x4078f9]

The problem is that, btrfs-map-logical always use sectorsize as default
block size to call alloc_extent_buffer.
And when it failes to find the block with the same size, it will free
the extent buffer in a incorrect method(Free and create a new one with
refs == 1).

2) Will return map result for non-exist extent.

 # btrfs-map-logical -l 1 -b 123456 /dev/sda6
 mirror 1 logical 1 physical 1 device /dev/sda6
 mirror 1 logical 4097 physical 4097 device /dev/sda6
 mirror 1 logical 8193 physical 8193 device /dev/sda6
 ...

Normally, before bytenr 12582912, there should be no extent as that's
the mkfs time temp metadata/system chunk.

But map-logical will still map them out.

Not to mention the 1 offset among all results.

[FIX]
This patch will rework the whole map logical by the following methods:
1) Always do things inside a extent
Even under the following case, map logical will only return covered
range in existing extents.

	|<------ range given ------->|
|<-Extent A->|	|<-Extent B->|	|<---Extent C->|
Result:
	|<-->|	|<---------->|	|<-->|

So with this patch, we will search extent tree to ensure all operation
are inside a extent before we do some stupid things.

2) No direct call on alloc_extent_buffer function.

That low-level function shouldn't be called at such high level.
It's only designed for low-level tree operation.

So in this patch we will only use safe high level functions avoid such
problem.

[RESULT]
With this patch, no assert will be triggered and better handle on
non-exist extents.

 # btrfs-map-logical -l 29622272 /dev/sda6
 mirror 1 logical 29622272 physical 38010880 device /dev/sda6
 mirror 2 logical 29622272 physical 1111752704 device /dev/sda6

 # btrfs-map-logical -l 1 -b 123456 /dev/sda6
 No extent found at range [1,123457)

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Qu Wenruo 2015-06-17 15:49:04 +08:00 committed by David Sterba
parent 1bbd40a1bb
commit eb81f8d263
1 changed files with 69 additions and 83 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

152
btrfs-map-logical.c
View File

@ -190,69 +190,6 @@ static int write_extent_content(struct btrfs_fs_info *fs_info, int out_fd,
return ret;
}
static struct extent_buffer * debug_read_block(struct btrfs_root *root,
u64 bytenr, u32 blocksize, u64 copy)
{
int ret;
struct extent_buffer *eb;
u64 length;
struct btrfs_multi_bio *multi = NULL;
struct btrfs_device *device;
int num_copies;
int mirror_num = 1;
eb = btrfs_find_create_tree_block(root, bytenr, blocksize);
if (!eb)
return NULL;
length = blocksize;
while (1) {
ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
eb->start, &length, &multi,
mirror_num, NULL);
if (ret) {
fprintf(info_file,
"Error: fails to map mirror%d logical %llu: %s\n",
mirror_num, (unsigned long long)eb->start,
strerror(-ret));
free_extent_buffer(eb);
return NULL;
}
device = multi->stripes[0].dev;
eb->fd = device->fd;
device->total_ios++;
eb->dev_bytenr = multi->stripes[0].physical;
fprintf(info_file, "mirror %d logical %Lu physical %Lu "
"device %s\n", mirror_num, (unsigned long long)bytenr,
(unsigned long long)eb->dev_bytenr, device->name);
kfree(multi);
if (!copy || mirror_num == copy) {
ret = read_extent_from_disk(eb, 0, eb->len);
if (ret) {
fprintf(info_file,
"Error: failed to read extent: mirror %d logical %llu: %s\n",
mirror_num, (unsigned long long)eb->start,
strerror(-ret));
free_extent_buffer(eb);
eb = NULL;
break;
}
}
num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
eb->start, eb->len);
if (num_copies == 1)
break;
mirror_num++;
if (mirror_num > num_copies)
break;
}
return eb;
}
static void print_usage(void) __attribute__((noreturn));
static void print_usage(void)
{
@ -268,14 +205,16 @@ int main(int ac, char **av)
{
struct cache_tree root_cache;
struct btrfs_root *root;
struct extent_buffer *eb;
char *dev;
char *output_file = NULL;
u64 logical = 0;
int ret = 0;
u64 copy = 0;
u64 logical = 0;
u64 bytes = 0;
int out_fd = 0;
u64 cur_logical = 0;
u64 cur_len = 0;
int out_fd = -1;
int found = 0;
int ret = 0;
while(1) {
int c;
@ -346,30 +285,77 @@ int main(int ac, char **av)
}
if (bytes == 0)
bytes = root->sectorsize;
bytes = root->nodesize;
cur_logical = logical;
cur_len = bytes;
bytes = (bytes + root->sectorsize - 1) / root->sectorsize;
bytes *= root->sectorsize;
while (bytes > 0) {
eb = debug_read_block(root, logical, root->sectorsize, copy);
if (eb && output_file) {
ret = write(out_fd, eb->data, eb->len);
if (ret < 0 || ret != eb->len) {
ret = 1;
fprintf(stderr, "output file write failed\n");
goto out_close_fd;
}
/* First find the nearest extent */
ret = map_one_extent(root->fs_info, &cur_logical, &cur_len, 0);
if (ret < 0) {
fprintf(stderr, "Failed to find extent at [%llu,%llu): %s\n",
cur_logical, cur_logical + cur_len, strerror(-ret));
goto out_close_fd;
}
/*
* Normally, search backward should be OK, but for special case like
* given logical is quite small where no extents are before it,
* we need to search forward.
*/
if (ret > 0) {
ret = map_one_extent(root->fs_info, &cur_logical, &cur_len, 1);
if (ret < 0) {
fprintf(stderr,
"Failed to find extent at [%llu,%llu): %s\n",
cur_logical, cur_logical + cur_len,
strerror(-ret));
goto out_close_fd;
}
if (ret > 0) {
fprintf(stderr,
"Failed to find any extent at [%llu,%llu)\n",
cur_logical, cur_logical + cur_len);
goto out_close_fd;
}
free_extent_buffer(eb);
logical += root->sectorsize;
bytes -= root->sectorsize;
}
while (cur_logical + cur_len >= logical && cur_logical < logical +
bytes) {
u64 real_logical;
u64 real_len;
found = 1;
ret = map_one_extent(root->fs_info, &cur_logical, &cur_len, 1);
if (ret < 0)
goto out_close_fd;
if (ret > 0)
break;
real_logical = max(logical, cur_logical);
real_len = min(logical + bytes, cur_logical + cur_len) -
real_logical;
ret = print_mapping_info(root->fs_info, real_logical, real_len);
if (ret < 0)
goto out_close_fd;
if (output_file && out_fd != -1) {
ret = write_extent_content(root->fs_info, out_fd,
real_logical, real_len, copy);
if (ret < 0)
goto out_close_fd;
}
cur_logical += cur_len;
}
if (!found) {
fprintf(stderr, "No extent found at range [%llu,%llu)\n",
logical, logical + bytes);
}
out_close_fd:
if (output_file && out_fd != 1)
close(out_fd);
close:
close_ctree(root);
if (ret < 0)
ret = 1;
return ret;
}