[[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@xxxxxxxxxxxxxx>
---
btrfs-map-logical.c | 148 ++++++++++++++++++++++++----------------------------
1 file changed, 67 insertions(+), 81 deletions(-)
diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c
index 1ee101c..a88e56e 100644
--- a/btrfs-map-logical.c
+++ b/btrfs-map-logical.c
@@ -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;
+
+ /* 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;
+ }
+ }
- bytes = (bytes + root->sectorsize - 1) / root->sectorsize;
- bytes *= root->sectorsize;
+ while (cur_logical + cur_len >= logical && cur_logical < logical +
+ bytes) {
+ u64 real_logical;
+ u64 real_len;
- 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");
+ 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;
- }
}
- free_extent_buffer(eb);
- logical += root->sectorsize;
- bytes -= root->sectorsize;
+
+ 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;
}
--
2.4.3
--
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