From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH 4/4] Btrfs: honor extent thresh during defragmentation Date: Fri, 02 Sep 2011 15:57:07 +0800 Message-ID: <4E608C53.9040304@cn.fujitsu.com> References: <4E608C29.10307@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: "linux-btrfs@vger.kernel.org" Return-path: In-Reply-To: <4E608C29.10307@cn.fujitsu.com> List-ID: We won't defrag an extent, if it's bigger than the threshold we specified and there's no small extent before it, but actually the code doesn't work this way. There are three bugs: - When should_defrag_range() decides we should keep on defragmenting an extent, last_len is not incremented. (old bug) - The length that passes to should_defrag_range() is not the length we're going to defrag. (new bug) - We always defrag 256K bytes data, and a big extent can be part of this range. (new bug) For a file with 4 extents: | 4K | 4K | 256K | 256K | The result of defrag with (the default) 256K extent thresh should be: | 264K | 256K | but with those bugs, we'll get: | 520K | Signed-off-by: Li Zefan --- fs/btrfs/ioctl.c | 37 ++++++++++++++++++++++++++----------- 1 files changed, 26 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 57aa5b7..90d7904 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -760,7 +760,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len, int ret = 1; /* - * make sure that once we start defragging and extent, we keep on + * make sure that once we start defragging an extent, we keep on * defragging it */ if (start < *defrag_end) @@ -805,7 +805,6 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len, * extent will force at least part of that big extent to be defragged. */ if (ret) { - *last_len += len; *defrag_end = extent_map_end(em); } else { *last_len = 0; @@ -978,13 +977,14 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, u64 skip = 0; u64 defrag_end = 0; u64 newer_off = range->start; - int newer_left = 0; unsigned long i; + unsigned long ra_index = 0; int ret; int defrag_count = 0; int compress_type = BTRFS_COMPRESS_ZLIB; int extent_thresh = range->extent_thresh; - int newer_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT; + int max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT; + int cluster = max_cluster; u64 new_align = ~((u64)128 * 1024 - 1); struct page **pages = NULL; @@ -1014,7 +1014,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, ra = &file->f_ra; } - pages = kmalloc(sizeof(struct page *) * newer_cluster, + pages = kmalloc(sizeof(struct page *) * max_cluster, GFP_NOFS); if (!pages) { ret = -ENOMEM; @@ -1039,7 +1039,6 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, * the extents in the file evenly spaced */ i = (newer_off & new_align) >> PAGE_CACHE_SHIFT; - newer_left = newer_cluster; } else goto out_ra; } else { @@ -1071,12 +1070,26 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, i = max(i + 1, next); continue; } + + if (!newer_than) { + cluster = (PAGE_CACHE_ALIGN(defrag_end) >> + PAGE_CACHE_SHIFT) - i; + cluster = min(cluster, max_cluster); + } else { + cluster = max_cluster; + } + if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS) BTRFS_I(inode)->force_compress = compress_type; - btrfs_force_ra(inode->i_mapping, ra, file, i, newer_cluster); + if (i + cluster > ra_index) { + ra_index = max(i, ra_index); + btrfs_force_ra(inode->i_mapping, ra, file, ra_index, + cluster); + ra_index += max_cluster; + } - ret = cluster_pages_for_defrag(inode, pages, i, newer_cluster); + ret = cluster_pages_for_defrag(inode, pages, i, cluster); if (ret < 0) goto out_ra; @@ -1096,15 +1109,17 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, if (!ret) { range->start = newer_off; i = (newer_off & new_align) >> PAGE_CACHE_SHIFT; - newer_left = newer_cluster; } else { break; } } else { - if (ret > 0) + if (ret > 0) { i += ret; - else + last_len += ret << PAGE_CACHE_SHIFT; + } else { i++; + last_len = 0; + } } } -- 1.7.3.1