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btrfs: simplify range tracking in cow_file_range()
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Simplify tracking of the range processed by using cur_alloc_size only to
store the reserved part that may fail to the allocated extent. Remove
the ram_size as well since it is always equal to cur_alloc_size in the
context. Advance the start in normal path until extent allocation
succeeds and keep the start unchanged in the error handling path.

Passed the fstest generic/475 test for a hundred times with quota
enabled. And a modified generic/475 test by removing the sleep time
for a hundred times. About one tenth of the tests do enter the error
handling path due to fail to reserve extent.

Suggested-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Haisu Wang <haisuwang@tencent.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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@kdave
Haisu Wang authored and kdave committed Nov 11, 2024
1 parent 7c855e1 commit 5599f39
Showing 1 changed file with 14 additions and 18 deletions.
32 changes: 14 additions & 18 deletions fs/btrfs/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1332,15 +1332,13 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
u64 alloc_hint = 0;
u64 orig_start = start;
u64 num_bytes;
unsigned long ram_size;
u64 cur_alloc_size = 0;
u64 min_alloc_size;
u64 blocksize = fs_info->sectorsize;
struct btrfs_key ins;
struct extent_map *em;
unsigned clear_bits;
unsigned long page_ops;
bool extent_reserved = false;
int ret = 0;

if (btrfs_is_free_space_inode(inode)) {
Expand Down Expand Up @@ -1394,8 +1392,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
struct btrfs_ordered_extent *ordered;
struct btrfs_file_extent file_extent;

cur_alloc_size = num_bytes;
ret = btrfs_reserve_extent(root, cur_alloc_size, cur_alloc_size,
ret = btrfs_reserve_extent(root, num_bytes, num_bytes,
min_alloc_size, 0, alloc_hint,
&ins, 1, 1);
if (ret == -EAGAIN) {
Expand Down Expand Up @@ -1426,24 +1423,22 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
if (ret < 0)
goto out_unlock;
cur_alloc_size = ins.offset;
extent_reserved = true;

ram_size = ins.offset;
file_extent.disk_bytenr = ins.objectid;
file_extent.disk_num_bytes = ins.offset;
file_extent.num_bytes = ins.offset;
file_extent.ram_bytes = ins.offset;
file_extent.offset = 0;
file_extent.compression = BTRFS_COMPRESS_NONE;

lock_extent(&inode->io_tree, start, start + ram_size - 1,
lock_extent(&inode->io_tree, start, start + cur_alloc_size - 1,
&cached);

em = btrfs_create_io_em(inode, start, &file_extent,
BTRFS_ORDERED_REGULAR);
if (IS_ERR(em)) {
unlock_extent(&inode->io_tree, start,
start + ram_size - 1, &cached);
start + cur_alloc_size - 1, &cached);
ret = PTR_ERR(em);
goto out_reserve;
}
Expand All @@ -1453,7 +1448,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
1 << BTRFS_ORDERED_REGULAR);
if (IS_ERR(ordered)) {
unlock_extent(&inode->io_tree, start,
start + ram_size - 1, &cached);
start + cur_alloc_size - 1, &cached);
ret = PTR_ERR(ordered);
goto out_drop_extent_cache;
}
Expand All @@ -1474,7 +1469,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
*/
if (ret)
btrfs_drop_extent_map_range(inode, start,
start + ram_size - 1,
start + cur_alloc_size - 1,
false);
}
btrfs_put_ordered_extent(ordered);
Expand All @@ -1492,7 +1487,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
page_ops = (keep_locked ? 0 : PAGE_UNLOCK);
page_ops |= PAGE_SET_ORDERED;

extent_clear_unlock_delalloc(inode, start, start + ram_size - 1,
extent_clear_unlock_delalloc(inode, start, start + cur_alloc_size - 1,
locked_folio, &cached,
EXTENT_LOCKED | EXTENT_DELALLOC,
page_ops);
Expand All @@ -1502,7 +1497,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
num_bytes -= cur_alloc_size;
alloc_hint = ins.objectid + ins.offset;
start += cur_alloc_size;
extent_reserved = false;
cur_alloc_size = 0;

/*
* btrfs_reloc_clone_csums() error, since start is increased
Expand All @@ -1518,7 +1513,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
return ret;

out_drop_extent_cache:
btrfs_drop_extent_map_range(inode, start, start + ram_size - 1, false);
btrfs_drop_extent_map_range(inode, start, start + cur_alloc_size - 1, false);
out_reserve:
btrfs_dec_block_group_reservations(fs_info, ins.objectid);
btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1);
Expand Down Expand Up @@ -1572,13 +1567,12 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
* to decrement again the data space_info's bytes_may_use counter,
* therefore we do not pass it the flag EXTENT_CLEAR_DATA_RESV.
*/
if (extent_reserved) {
if (cur_alloc_size) {
extent_clear_unlock_delalloc(inode, start,
start + cur_alloc_size - 1,
locked_folio, &cached, clear_bits,
page_ops);
btrfs_qgroup_free_data(inode, NULL, start, cur_alloc_size, NULL);
start += cur_alloc_size;
}

/*
Expand All @@ -1587,11 +1581,13 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
* space_info's bytes_may_use counter, reserved in
* btrfs_check_data_free_space().
*/
if (start < end) {
if (start + cur_alloc_size < end) {
clear_bits |= EXTENT_CLEAR_DATA_RESV;
extent_clear_unlock_delalloc(inode, start, end, locked_folio,
extent_clear_unlock_delalloc(inode, start + cur_alloc_size,
end, locked_folio,
&cached, clear_bits, page_ops);
btrfs_qgroup_free_data(inode, NULL, start, end - start + 1, NULL);
btrfs_qgroup_free_data(inode, NULL, start + cur_alloc_size,
end - start - cur_alloc_size + 1, NULL);
}
return ret;
}
Expand Down

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