Btrfs: fix defrag regression
If a file has 3 small extents:
| ext1 | ext2 | ext3 |
Running "btrfs fi defrag" will only defrag the last two extents, if those
extent mappings hasn't been read into memory from disk.
This bug was introduced by commit 17ce6ef8d7
("Btrfs: add a check to decide if we should defrag the range")
The cause is, that commit looked into previous and next extents using
lookup_extent_mapping() only.
While at it, remove the code that checks the previous extent, since
it's sufficient to check the next extent.
Signed-off-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
101
fs/btrfs/ioctl.c
101
fs/btrfs/ioctl.c
@@ -786,48 +786,12 @@ none:
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return -ENOENT;
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return -ENOENT;
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}
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}
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/*
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static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
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* Validaty check of prev em and next em:
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* 1) no prev/next em
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* 2) prev/next em is an hole/inline extent
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*/
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static int check_adjacent_extents(struct inode *inode, struct extent_map *em)
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{
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{
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struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
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struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
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struct extent_map *prev = NULL, *next = NULL;
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int ret = 0;
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read_lock(&em_tree->lock);
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prev = lookup_extent_mapping(em_tree, em->start - 1, (u64)-1);
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next = lookup_extent_mapping(em_tree, em->start + em->len, (u64)-1);
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read_unlock(&em_tree->lock);
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if ((!prev || prev->block_start >= EXTENT_MAP_LAST_BYTE) &&
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(!next || next->block_start >= EXTENT_MAP_LAST_BYTE))
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ret = 1;
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free_extent_map(prev);
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free_extent_map(next);
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return ret;
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}
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static int should_defrag_range(struct inode *inode, u64 start, u64 len,
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int thresh, u64 *last_len, u64 *skip,
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u64 *defrag_end)
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{
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struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
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struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
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struct extent_map *em = NULL;
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struct extent_map *em;
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struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
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u64 len = PAGE_CACHE_SIZE;
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int ret = 1;
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/*
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* make sure that once we start defragging an extent, we keep on
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* defragging it
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*/
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if (start < *defrag_end)
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return 1;
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*skip = 0;
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/*
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/*
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* hopefully we have this extent in the tree already, try without
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* hopefully we have this extent in the tree already, try without
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@@ -844,27 +808,64 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
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unlock_extent(io_tree, start, start + len - 1);
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unlock_extent(io_tree, start, start + len - 1);
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if (IS_ERR(em))
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if (IS_ERR(em))
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return 0;
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return NULL;
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}
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}
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return em;
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}
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static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
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{
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struct extent_map *next;
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bool ret = true;
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/* this is the last extent */
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if (em->start + em->len >= i_size_read(inode))
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return false;
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next = defrag_lookup_extent(inode, em->start + em->len);
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if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
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ret = false;
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free_extent_map(next);
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return ret;
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}
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static int should_defrag_range(struct inode *inode, u64 start, int thresh,
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u64 *last_len, u64 *skip, u64 *defrag_end)
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{
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struct extent_map *em;
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int ret = 1;
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bool next_mergeable = true;
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/*
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* make sure that once we start defragging an extent, we keep on
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* defragging it
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*/
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if (start < *defrag_end)
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return 1;
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*skip = 0;
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em = defrag_lookup_extent(inode, start);
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if (!em)
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return 0;
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/* this will cover holes, and inline extents */
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/* this will cover holes, and inline extents */
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if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
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if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
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ret = 0;
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ret = 0;
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goto out;
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goto out;
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}
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}
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/* If we have nothing to merge with us, just skip. */
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next_mergeable = defrag_check_next_extent(inode, em);
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if (check_adjacent_extents(inode, em)) {
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ret = 0;
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goto out;
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}
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/*
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/*
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* we hit a real extent, if it is big don't bother defragging it again
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* we hit a real extent, if it is big or the next extent is not a
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* real extent, don't bother defragging it
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*/
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*/
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if ((*last_len == 0 || *last_len >= thresh) && em->len >= thresh)
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if ((*last_len == 0 || *last_len >= thresh) &&
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(em->len >= thresh || !next_mergeable))
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ret = 0;
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ret = 0;
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out:
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out:
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/*
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/*
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* last_len ends up being a counter of how many bytes we've defragged.
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* last_len ends up being a counter of how many bytes we've defragged.
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@@ -1143,8 +1144,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
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break;
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break;
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if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
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if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, extent_thresh,
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extent_thresh, &last_len, &skip,
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&last_len, &skip, &defrag_end)) {
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&defrag_end)) {
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unsigned long next;
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unsigned long next;
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/*
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/*
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* the should_defrag function tells us how much to skip
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* the should_defrag function tells us how much to skip
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