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btrfs: make relocate_one_page() handle subpage case 

For subpage case, one page of data reloc inode can contain several file
extents, like this:

|<--- File extent A --->| FE B | FE C |<--- File extent D -->|
		|<--------- Page --------->|

We can no longer use PAGE_SIZE directly for various operations.

This patch will relocate_one_page() to handle subpage case by:
- Iterating through all extents of a cluster when marking pages
  When marking pages dirty and delalloc, we need to check the cluster
  extent boundary.
  Now we introduce a loop to go extent by extent of a page, until we
  either finished the last extent, or reach the page end.

  By this, regular sectorsize == PAGE_SIZE can still work as usual, since
  we will do that loop only once.

- Iteration start from max(page_start, extent_start)
  Since we can have the following case:
			| FE B | FE C |<--- File extent D -->|
		|<--------- Page --------->|
  Thus we can't always start from page_start, but do a
  max(page_start, extent_start)

- Iteration end when the cluster is exhausted
  Similar to previous case, the last file extent can end before the page
  end:
|<--- File extent A --->| FE B | FE C |
		|<--------- Page --------->|
  In this case, we need to manually exit the loop after we have finished
  the last extent of the cluster.

- Reserve metadata space for each extent range
  Since now we can hit multiple ranges in one page, we should reserve
  metadata for each range, not simply PAGE_SIZE.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2021-07-26 14:34:57 +08:00 committed by David Sterba
parent f47960f49e
commit c283289812
1 changed files with 78 additions and 30 deletions
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108
fs/btrfs/relocation.c
View File

@ -24,6 +24,7 @@
#include "block-group.h"
#include "backref.h"
#include "misc.h"
#include "subpage.h"
/*
* Relocation overview
@ -2886,6 +2887,17 @@ noinline int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
}
ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
static u64 get_cluster_boundary_end(struct file_extent_cluster *cluster,
int cluster_nr)
{
/* Last extent, use cluster end directly */
if (cluster_nr >= cluster->nr - 1)
return cluster->end;
/* Use next boundary start*/
return cluster->boundary[cluster_nr + 1] - 1;
}
static int relocate_one_page(struct inode *inode, struct file_ra_state *ra,
struct file_extent_cluster *cluster,
int *cluster_nr, unsigned long page_index)
@ -2897,22 +2909,17 @@ static int relocate_one_page(struct inode *inode, struct file_ra_state *ra,
struct page *page;
u64 page_start;
u64 page_end;
u64 cur;
int ret;
ASSERT(page_index <= last_index);
ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), PAGE_SIZE);
if (ret)
return ret;
page = find_lock_page(inode->i_mapping, page_index);
if (!page) {
page_cache_sync_readahead(inode->i_mapping, ra, NULL,
page_index, last_index + 1 - page_index);
page = find_or_create_page(inode->i_mapping, page_index, mask);
if (!page) {
ret = -ENOMEM;
goto release_delalloc;
}
if (!page)
return -ENOMEM;
}
ret = set_page_extent_mapped(page);
if (ret < 0)
@ -2934,30 +2941,74 @@ static int relocate_one_page(struct inode *inode, struct file_ra_state *ra,
page_start = page_offset(page);
page_end = page_start + PAGE_SIZE - 1;
lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
/*
* Start from the cluster, as for subpage case, the cluster can start
* inside the page.
*/
cur = max(page_start, cluster->boundary[*cluster_nr] - offset);
while (cur <= page_end) {
u64 extent_start = cluster->boundary[*cluster_nr] - offset;
u64 extent_end = get_cluster_boundary_end(cluster,
*cluster_nr) - offset;
u64 clamped_start = max(page_start, extent_start);
u64 clamped_end = min(page_end, extent_end);
u32 clamped_len = clamped_end + 1 - clamped_start;
if (*cluster_nr < cluster->nr &&
page_start + offset == cluster->boundary[*cluster_nr]) {
set_extent_bits(&BTRFS_I(inode)->io_tree, page_start, page_end,
EXTENT_BOUNDARY);
(*cluster_nr)++;
/* Reserve metadata for this range */
ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
clamped_len);
if (ret)
goto release_page;
/* Mark the range delalloc and dirty for later writeback */
lock_extent(&BTRFS_I(inode)->io_tree, clamped_start, clamped_end);
ret = btrfs_set_extent_delalloc(BTRFS_I(inode), clamped_start,
clamped_end, 0, NULL);
if (ret) {
clear_extent_bits(&BTRFS_I(inode)->io_tree,
clamped_start, clamped_end,
EXTENT_LOCKED | EXTENT_BOUNDARY);
btrfs_delalloc_release_metadata(BTRFS_I(inode),
clamped_len, true);
btrfs_delalloc_release_extents(BTRFS_I(inode),
clamped_len);
goto release_page;
}
btrfs_page_set_dirty(fs_info, page, clamped_start, clamped_len);
/*
* Set the boundary if it's inside the page.
* Data relocation requires the destination extents to have the
* same size as the source.
* EXTENT_BOUNDARY bit prevents current extent from being merged
* with previous extent.
*/
if (in_range(cluster->boundary[*cluster_nr] - offset,
page_start, PAGE_SIZE)) {
u64 boundary_start = cluster->boundary[*cluster_nr] -
offset;
u64 boundary_end = boundary_start +
fs_info->sectorsize - 1;
set_extent_bits(&BTRFS_I(inode)->io_tree,
boundary_start, boundary_end,
EXTENT_BOUNDARY);
}
unlock_extent(&BTRFS_I(inode)->io_tree, clamped_start, clamped_end);
btrfs_delalloc_release_extents(BTRFS_I(inode), clamped_len);
cur += clamped_len;
/* Crossed extent end, go to next extent */
if (cur >= extent_end) {
(*cluster_nr)++;
/* Just finished the last extent of the cluster, exit. */
if (*cluster_nr >= cluster->nr)
break;
}
}
ret = btrfs_set_extent_delalloc(BTRFS_I(inode), page_start, page_end,
0, NULL);
if (ret) {
clear_extent_bits(&BTRFS_I(inode)->io_tree, page_start,
page_end, EXTENT_LOCKED | EXTENT_BOUNDARY);
goto release_page;
}
set_page_dirty(page);
unlock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
unlock_page(page);
put_page(page);
btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
balance_dirty_pages_ratelimited(inode->i_mapping);
btrfs_throttle(fs_info);
if (btrfs_should_cancel_balance(fs_info))
@ -2967,9 +3018,6 @@ static int relocate_one_page(struct inode *inode, struct file_ra_state *ra,
release_page:
unlock_page(page);
put_page(page);
release_delalloc:
btrfs_delalloc_release_metadata(BTRFS_I(inode), PAGE_SIZE, true);
btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
return ret;
}