From: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
This issue was revealed by modifying BTRFS_MAX_EXTENT_SIZE(128MB) to 64KB,
When modifying BTRFS_MAX_EXTENT_SIZE(128MB) to 64KB, fsstress test often
gets these warnings from btrfs_destroy_inode():
WARN_ON(BTRFS_I(inode)->outstanding_extents);
WARN_ON(BTRFS_I(inode)->reserved_extents);
Simple test program below can reproduce this issue steadily.
Note: you need to modify BTRFS_MAX_EXTENT_SIZE to 64KB to have test,
otherwise there won't be such WARNING.
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main(void)
{
int fd;
char buf[68 *1024];
memset(buf, 0, 68 * 1024);
fd = open("testfile", O_CREAT | O_EXCL | O_RDWR);
pwrite(fd, buf, 68 * 1024, 64 * 1024);
return;
}
When BTRFS_MAX_EXTENT_SIZE is 64KB, and buffered data range is:
64KB 128K 132KB
|-----------------------------------------------|---------------|
64 + 4KB
1) for above data range, btrfs_delalloc_reserve_metadata() will reserve
metadata and set BTRFS_I(inode)->outstanding_extents to 2.
(68KB + 64KB - 1) / 64KB == 2
Outstanding_extents: 2
2) then btrfs_dirty_page() will be called to dirty pages and set
EXTENT_DELALLOC flag. In this case, btrfs_set_bit_hook() will be called
twice.
The 1st set_bit_hook() call will set DEALLOC flag for the first 64K.
64KB 128KB
|-----------------------------------------------|
64KB DELALLOC
Outstanding_extents: 2
Set_bit_hooks() uses FIRST_DELALLOC flag to avoid re-increase
outstanding_extents counter.
So for 1st set_bit_hooks() call, it won't modify outstanding_extents,
it's still 2.
Then FIRST_DELALLOC flag is *CLEARED*.
3) 2nd btrfs_set_bit_hook() call.
Because FIRST_DELALLOC have been cleared by previous set_bit_hook(),
btrfs_set_bit_hook() will increase BTRFS_I(inode)->outstanding_extents by
one, so now BTRFS_I(inode)->outstanding_extents is 3.
64KB 128KB 132KB
|-----------------------------------------------|----------------|
64K DELALLOC 4K DELALLOC
Outstanding_extents: 3
But the correct outstanding_extents number should be 2, not 3.
The 2nd btrfs_set_bit_hook() call just screwed up this, and leads to the
WARN_ON().
Normally, we can solve it by only increasing outstanding_extents in
set_bit_hook().
But the problem is for delalloc_reserve/release_metadata(), we only have
a 'length' parameter, and calculate in-accurate outstanding_extents.
If we only rely on set_bit_hook() release_metadata() will crew things up
as it will decrease inaccurate number.
So the fix we use is:
1) Increase *INACCURATE* outstanding_extents at delalloc_reserve_meta
Just as a place holder.
2) Increase *accurate* outstanding_extents at set_bit_hooks()
This is the real increaser.
3) Decrease *INACCURATE* outstanding_extents before returning
This makes outstanding_extents to correct value.
For 128M BTRFS_MAX_EXTENT_SIZE, due to limitation of
__btrfs_buffered_write(), each iteration will only handle about 2MB
data.
So btrfs_dirty_pages() won't need to handle cases cross 2 extents.
Cc: Mark Fasheh <mfasheh@xxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxx>
Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/inode.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
fs/btrfs/ioctl.c | 6 ++---
3 files changed, 66 insertions(+), 10 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a513433..ec6b61b 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3094,6 +3094,8 @@ int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int delay_iput,
int nr);
int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
struct extent_state **cached_state);
+int btrfs_set_extent_defrag(struct inode *inode, u64 start, u64 end,
+ struct extent_state **cached_state);
int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
struct btrfs_root *new_root,
struct btrfs_root *parent_root,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b83e322..ff9f8a8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1729,11 +1729,15 @@ static void btrfs_split_extent_hook(struct inode *inode,
struct extent_state *orig, u64 split)
{
u64 size;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
/* not delalloc, ignore it */
if (!(orig->state & EXTENT_DELALLOC))
return;
+ if (root == root->fs_info->tree_root)
+ return;
+
size = orig->end - orig->start + 1;
if (size > BTRFS_MAX_EXTENT_SIZE) {
u64 num_extents;
@@ -1771,11 +1775,15 @@ static void btrfs_merge_extent_hook(struct inode *inode,
{
u64 new_size, old_size;
u64 num_extents;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
/* not delalloc, ignore it */
if (!(other->state & EXTENT_DELALLOC))
return;
+ if (root == root->fs_info->tree_root)
+ return;
+
if (new->start > other->start)
new_size = new->end - other->start + 1;
else
@@ -1882,13 +1890,16 @@ static void btrfs_set_bit_hook(struct inode *inode,
if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
struct btrfs_root *root = BTRFS_I(inode)->root;
u64 len = state->end + 1 - state->start;
+ u64 num_extents = div64_u64(len + BTRFS_MAX_EXTENT_SIZE - 1,
+ BTRFS_MAX_EXTENT_SIZE);
bool do_list = !btrfs_is_free_space_inode(inode);
- if (*bits & EXTENT_FIRST_DELALLOC) {
+ if (*bits & EXTENT_FIRST_DELALLOC)
*bits &= ~EXTENT_FIRST_DELALLOC;
- } else {
+
+ if (root != root->fs_info->tree_root) {
spin_lock(&BTRFS_I(inode)->lock);
- BTRFS_I(inode)->outstanding_extents++;
+ BTRFS_I(inode)->outstanding_extents += num_extents;
spin_unlock(&BTRFS_I(inode)->lock);
}
@@ -1936,7 +1947,7 @@ static void btrfs_clear_bit_hook(struct inode *inode,
if (*bits & EXTENT_FIRST_DELALLOC) {
*bits &= ~EXTENT_FIRST_DELALLOC;
- } else if (!(*bits & EXTENT_DO_ACCOUNTING)) {
+ } else if (!(*bits & EXTENT_DO_ACCOUNTING) && do_list) {
spin_lock(&BTRFS_I(inode)->lock);
BTRFS_I(inode)->outstanding_extents -= num_extents;
spin_unlock(&BTRFS_I(inode)->lock);
@@ -2129,9 +2140,54 @@ static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
struct extent_state **cached_state)
{
+ int ret;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ u64 num_extents = div64_u64(end - start + BTRFS_MAX_EXTENT_SIZE,
+ BTRFS_MAX_EXTENT_SIZE);
+
WARN_ON((end & (PAGE_SIZE - 1)) == 0);
- return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
- cached_state);
+ ret = set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
+ cached_state);
+
+ /*
+ * btrfs_delalloc_reserve_metadata() will first add number of
+ * outstanding extents according to data length, which is inaccurate
+ * for case like dirtying already dirty pages.
+ * so here we will decrease such inaccurate numbers, to make
+ * outstanding_extents only rely on the correct values added by
+ * set_bit_hook()
+ *
+ * Also, we skipped the metadata space reserve for space cache inodes,
+ * so don't modify the outstanding_extents value.
+ */
+ if (ret == 0 && root != root->fs_info->tree_root) {
+ spin_lock(&BTRFS_I(inode)->lock);
+ BTRFS_I(inode)->outstanding_extents -= num_extents;
+ spin_unlock(&BTRFS_I(inode)->lock);
+ }
+
+ return ret;
+}
+
+int btrfs_set_extent_defrag(struct inode *inode, u64 start, u64 end,
+ struct extent_state **cached_state)
+{
+ int ret;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ u64 num_extents = div64_u64(end - start + BTRFS_MAX_EXTENT_SIZE,
+ BTRFS_MAX_EXTENT_SIZE);
+
+ WARN_ON((end & (PAGE_SIZE - 1)) == 0);
+ ret = set_extent_defrag(&BTRFS_I(inode)->io_tree, start, end,
+ cached_state);
+
+ if (ret == 0 && root != root->fs_info->tree_root) {
+ spin_lock(&BTRFS_I(inode)->lock);
+ BTRFS_I(inode)->outstanding_extents -= num_extents;
+ spin_unlock(&BTRFS_I(inode)->lock);
+ }
+
+ return ret;
}
/* see btrfs_writepage_start_hook for details on why this is required */
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 74e2cef0..b9bc0de 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1236,10 +1236,8 @@ again:
(page_cnt - i_done) << PAGE_SHIFT);
}
-
- set_extent_defrag(&BTRFS_I(inode)->io_tree, page_start, page_end - 1,
- &cached_state);
-
+ btrfs_set_extent_defrag(inode, page_start,
+ page_end - 1, &cached_state);
unlock_extent_cached(&BTRFS_I(inode)->io_tree,
page_start, page_end - 1, &cached_state,
GFP_NOFS);
--
2.9.0
--
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