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Btrfs: switch extent_map to a rw lock

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There are two main users of the extent_map tree.  The
first is regular file inodes, where it is evenly spread
between readers and writers.

The second is the chunk allocation tree, which maps blocks from
logical addresses to phyiscal ones, and it is 99.99% reads.

The mapping tree is a point of lock contention during heavy IO
workloads, so this commit switches things to a rw lock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2009-09-02 16:24:52 -04:00
parent 57fd5a5ff8
commit 890871be85
10 changed files with 57 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
fs/btrfs/inode.c
View File

@ -612,9 +612,9 @@ static noinline int submit_compressed_extents(struct inode *inode,
set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
while (1) {
spin_lock(&em_tree->lock);
write_lock(&em_tree->lock);
ret = add_extent_mapping(em_tree, em);
spin_unlock(&em_tree->lock);
write_unlock(&em_tree->lock);
if (ret != -EEXIST) {
free_extent_map(em);
break;
@ -748,9 +748,9 @@ static noinline int cow_file_range(struct inode *inode,
set_bit(EXTENT_FLAG_PINNED, &em->flags);
while (1) {
spin_lock(&em_tree->lock);
write_lock(&em_tree->lock);
ret = add_extent_mapping(em_tree, em);
spin_unlock(&em_tree->lock);
write_unlock(&em_tree->lock);
if (ret != -EEXIST) {
free_extent_map(em);
break;
@ -1081,9 +1081,9 @@ out_check:
em->bdev = root->fs_info->fs_devices->latest_bdev;
set_bit(EXTENT_FLAG_PINNED, &em->flags);
while (1) {
spin_lock(&em_tree->lock);
write_lock(&em_tree->lock);
ret = add_extent_mapping(em_tree, em);
spin_unlock(&em_tree->lock);
write_unlock(&em_tree->lock);
if (ret != -EEXIST) {
free_extent_map(em);
break;
@ -1670,13 +1670,13 @@ static int btrfs_io_failed_hook(struct bio *failed_bio,
failrec->last_mirror = 0;
failrec->bio_flags = 0;
spin_lock(&em_tree->lock);
read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, start, failrec->len);
if (em->start > start || em->start + em->len < start) {
free_extent_map(em);
em = NULL;
}
spin_unlock(&em_tree->lock);
read_unlock(&em_tree->lock);
if (!em || IS_ERR(em)) {
kfree(failrec);
@ -4069,11 +4069,11 @@ struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
int compressed;
again:
spin_lock(&em_tree->lock);
read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, start, len);
if (em)
em->bdev = root->fs_info->fs_devices->latest_bdev;
spin_unlock(&em_tree->lock);
read_unlock(&em_tree->lock);
if (em) {
if (em->start > start || em->start + em->len <= start)
@ -4264,7 +4264,7 @@ insert:
}
err = 0;
spin_lock(&em_tree->lock);
write_lock(&em_tree->lock);
ret = add_extent_mapping(em_tree, em);
/* it is possible that someone inserted the extent into the tree
* while we had the lock dropped. It is also possible that
@ -4304,7 +4304,7 @@ insert:
err = 0;
}
}
spin_unlock(&em_tree->lock);
write_unlock(&em_tree->lock);
out:
if (path)
btrfs_free_path(path);