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btrfs: defrag: introduce helper to defrag a range 

A new helper, defrag_one_range(), is introduced to defrag one range.

This function will mostly prepare the needed pages and extent status for
defrag_one_locked_target().

As we can only have a consistent view of extent map with page and extent
bits locked, we need to re-check the range passed in to get a real
target list for defrag_one_locked_target().

Since defrag_collect_targets() will call defrag_lookup_extent() and lock
extent range, we also need to teach those two functions to skip extent
lock.  Thus new parameter, @locked, is introduced to skip extent lock if
the caller has already locked the range.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2021-08-06 16:12:38 +08:00 committed by David Sterba
parent 22b398eeee
commit e9eec72151
1 changed files with 93 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

103
fs/btrfs/ioctl.c
View File

@ -1087,7 +1087,8 @@ none:
return -ENOENT;
}
static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
bool locked)
{
struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
@ -1107,9 +1108,11 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
u64 end = start + sectorsize - 1;
/* get the big lock and read metadata off disk */
lock_extent_bits(io_tree, start, end, &cached);
if (!locked)
lock_extent_bits(io_tree, start, end, &cached);
em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, sectorsize);
unlock_extent_cached(io_tree, start, end, &cached);
if (!locked)
unlock_extent_cached(io_tree, start, end, &cached);
if (IS_ERR(em))
return NULL;
@ -1118,7 +1121,8 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
return em;
}
static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em,
bool locked)
{
struct extent_map *next;
bool ret = true;
@ -1127,7 +1131,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
if (em->start + em->len >= i_size_read(inode))
return false;
next = defrag_lookup_extent(inode, em->start + em->len);
next = defrag_lookup_extent(inode, em->start + em->len, locked);
if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
ret = false;
else if ((em->block_start + em->block_len == next->block_start) &&
@ -1156,7 +1160,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
*skip = 0;
em = defrag_lookup_extent(inode, start);
em = defrag_lookup_extent(inode, start, false);
if (!em)
return 0;
@ -1169,7 +1173,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
if (!*defrag_end)
prev_mergeable = false;
next_mergeable = defrag_check_next_extent(inode, em);
next_mergeable = defrag_check_next_extent(inode, em, false);
/*
* we hit a real extent, if it is big or the next extent is not a
* real extent, don't bother defragging it
@ -1449,12 +1453,13 @@ struct defrag_target_range {
* @do_compress: whether the defrag is doing compression
* if true, @extent_thresh will be ignored and all regular
* file extents meeting @newer_than will be targets.
* @locked: if the range has already held extent lock
* @target_list: list of targets file extents
*/
static int defrag_collect_targets(struct btrfs_inode *inode,
u64 start, u64 len, u32 extent_thresh,
u64 newer_than, bool do_compress,
struct list_head *target_list)
bool locked, struct list_head *target_list)
{
u64 cur = start;
int ret = 0;
@ -1465,7 +1470,7 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
bool next_mergeable = true;
u64 range_len;
em = defrag_lookup_extent(&inode->vfs_inode, cur);
em = defrag_lookup_extent(&inode->vfs_inode, cur, locked);
if (!em)
break;
@ -1489,7 +1494,8 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
if (em->len >= extent_thresh)
goto next;
next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em);
next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em,
locked);
if (!next_mergeable) {
struct defrag_target_range *last;
@ -1606,6 +1612,83 @@ static int defrag_one_locked_target(struct btrfs_inode *inode,
return ret;
}
static int defrag_one_range(struct btrfs_inode *inode, u64 start, u32 len,
u32 extent_thresh, u64 newer_than, bool do_compress)
{
struct extent_state *cached_state = NULL;
struct defrag_target_range *entry;
struct defrag_target_range *tmp;
LIST_HEAD(target_list);
struct page **pages;
const u32 sectorsize = inode->root->fs_info->sectorsize;
u64 last_index = (start + len - 1) >> PAGE_SHIFT;
u64 start_index = start >> PAGE_SHIFT;
unsigned int nr_pages = last_index - start_index + 1;
int ret = 0;
int i;
ASSERT(nr_pages <= CLUSTER_SIZE / PAGE_SIZE);
ASSERT(IS_ALIGNED(start, sectorsize) && IS_ALIGNED(len, sectorsize));
pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
if (!pages)
return -ENOMEM;
/* Prepare all pages */
for (i = 0; i < nr_pages; i++) {
pages[i] = defrag_prepare_one_page(inode, start_index + i);
if (IS_ERR(pages[i])) {
ret = PTR_ERR(pages[i]);
pages[i] = NULL;
goto free_pages;
}
}
for (i = 0; i < nr_pages; i++)
wait_on_page_writeback(pages[i]);
/* Lock the pages range */
lock_extent_bits(&inode->io_tree, start_index << PAGE_SHIFT,
(last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
&cached_state);
/*
* Now we have a consistent view about the extent map, re-check
* which range really needs to be defragged.
*
* And this time we have extent locked already, pass @locked = true
* so that we won't relock the extent range and cause deadlock.
*/
ret = defrag_collect_targets(inode, start, len, extent_thresh,
newer_than, do_compress, true,
&target_list);
if (ret < 0)
goto unlock_extent;
list_for_each_entry(entry, &target_list, list) {
ret = defrag_one_locked_target(inode, entry, pages, nr_pages,
&cached_state);
if (ret < 0)
break;
}
list_for_each_entry_safe(entry, tmp, &target_list, list) {
list_del_init(&entry->list);
kfree(entry);
}
unlock_extent:
unlock_extent_cached(&inode->io_tree, start_index << PAGE_SHIFT,
(last_index << PAGE_SHIFT) + PAGE_SIZE - 1,
&cached_state);
free_pages:
for (i = 0; i < nr_pages; i++) {
if (pages[i]) {
unlock_page(pages[i]);
put_page(pages[i]);
}
}
kfree(pages);
return ret;
}
/*
* Entry point to file defragmentation.
*