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btrfs: use on-stack variable for block reserve in btrfs_truncate()

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We can avoid potential memory allocation failure in btrfs_truncate() as
the block reserve lifetime is limited to the scope of the function. This
requires +48 bytes on stack.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2025-06-04 11:29:25 +02:00
parent ec41c34547
commit 7ce22f62b2
1 changed files with 10 additions and 12 deletions
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22
fs/btrfs/inode.c
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@ -7606,7 +7606,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
};
struct btrfs_root *root = inode->root;
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_block_rsv *rsv;
struct btrfs_block_rsv rsv;
int ret;
struct btrfs_trans_handle *trans;
u64 mask = fs_info->sectorsize - 1;
@ -7648,11 +7648,9 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
* 2) fs_info->trans_block_rsv - this will have 1 items worth left for
* updating the inode.
*/
rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);
if (!rsv)
return -ENOMEM;
rsv->size = min_size;
rsv->failfast = true;
btrfs_init_metadata_block_rsv(fs_info, &rsv, BTRFS_BLOCK_RSV_TEMP);
rsv.size = min_size;
rsv.failfast = true;
/*
* 1 for the truncate slack space
@ -7665,7 +7663,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
}
/* Migrate the slack space for the truncate to our reserve */
ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,
ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, &rsv,
min_size, false);
/*
* We have reserved 2 metadata units when we started the transaction and
@ -7677,7 +7675,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
goto out;
}
trans->block_rsv = rsv;
trans->block_rsv = &rsv;
while (1) {
struct extent_state *cached_state = NULL;
@ -7720,9 +7718,9 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
break;
}
btrfs_block_rsv_release(fs_info, rsv, -1, NULL);
btrfs_block_rsv_release(fs_info, &rsv, -1, NULL);
ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,
rsv, min_size, false);
&rsv, min_size, false);
/*
* We have reserved 2 metadata units when we started the
* transaction and min_size matches 1 unit, so this should never
@ -7731,7 +7729,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
if (WARN_ON(ret))
break;
trans->block_rsv = rsv;
trans->block_rsv = &rsv;
}
/*
@ -7770,7 +7768,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback)
btrfs_btree_balance_dirty(fs_info);
}
out:
btrfs_free_block_rsv(fs_info, rsv);
btrfs_block_rsv_release(fs_info, &rsv, (u64)-1, NULL);
/*
* So if we truncate and then write and fsync we normally would just
* write the extents that changed, which is a problem if we need to