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Btrfs: reduce extent_state lock contention for metadata 

For metadata buffers that don't straddle pages (all of them), btrfs
can safely use the page uptodate bits and extent_buffer uptodate bit
instead of needing to use the extent_state tree.

This greatly reduces contention on the state tree lock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2011-07-25 06:50:50 -04:00
parent 31533fb263
commit 19b6caf4ac
1 changed files with 41 additions and 14 deletions
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55
fs/btrfs/extent_io.c
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@ -3268,6 +3268,22 @@ int set_extent_buffer_dirty(struct extent_io_tree *tree,
return was_dirty;
}
static int __eb_straddles_pages(u64 start, u64 len)
{
if (len < PAGE_CACHE_SIZE)
return 1;
if (start & (PAGE_CACHE_SIZE - 1))
return 1;
if ((start + len) & (PAGE_CACHE_SIZE - 1))
return 1;
return 0;
}
static int eb_straddles_pages(struct extent_buffer *eb)
{
return __eb_straddles_pages(eb->start, eb->len);
}
int clear_extent_buffer_uptodate(struct extent_io_tree *tree,
struct extent_buffer *eb,
struct extent_state **cached_state)
@ -3279,8 +3295,10 @@ int clear_extent_buffer_uptodate(struct extent_io_tree *tree,
num_pages = num_extent_pages(eb->start, eb->len);
clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
clear_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
cached_state, GFP_NOFS);
if (eb_straddles_pages(eb)) {
clear_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
cached_state, GFP_NOFS);
}
for (i = 0; i < num_pages; i++) {
page = extent_buffer_page(eb, i);
if (page)
@ -3298,8 +3316,10 @@ int set_extent_buffer_uptodate(struct extent_io_tree *tree,
num_pages = num_extent_pages(eb->start, eb->len);
set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
NULL, GFP_NOFS);
if (eb_straddles_pages(eb)) {
set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
NULL, GFP_NOFS);
}
for (i = 0; i < num_pages; i++) {
page = extent_buffer_page(eb, i);
if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
@ -3322,9 +3342,12 @@ int extent_range_uptodate(struct extent_io_tree *tree,
int uptodate;
unsigned long index;
ret = test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL);
if (ret)
return 1;
if (__eb_straddles_pages(start, end - start + 1)) {
ret = test_range_bit(tree, start, end,
EXTENT_UPTODATE, 1, NULL);
if (ret)
return 1;
}
while (start <= end) {
index = start >> PAGE_CACHE_SHIFT;
page = find_get_page(tree->mapping, index);
@ -3352,10 +3375,12 @@ int extent_buffer_uptodate(struct extent_io_tree *tree,
if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
return 1;
ret = test_range_bit(tree, eb->start, eb->start + eb->len - 1,
EXTENT_UPTODATE, 1, cached_state);
if (ret)
return ret;
if (eb_straddles_pages(eb)) {
ret = test_range_bit(tree, eb->start, eb->start + eb->len - 1,
EXTENT_UPTODATE, 1, cached_state);
if (ret)
return ret;
}
num_pages = num_extent_pages(eb->start, eb->len);
for (i = 0; i < num_pages; i++) {
@ -3388,9 +3413,11 @@ int read_extent_buffer_pages(struct extent_io_tree *tree,
if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
return 0;
if (test_range_bit(tree, eb->start, eb->start + eb->len - 1,
EXTENT_UPTODATE, 1, NULL)) {
return 0;
if (eb_straddles_pages(eb)) {
if (test_range_bit(tree, eb->start, eb->start + eb->len - 1,
EXTENT_UPTODATE, 1, NULL)) {
return 0;
}
}
if (start) {