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Btrfs: optimize read_block_for_search 

This patch does two things, first it only does one call to
btrfs_buffer_uptodate() with the gen specified instead of once with 0 and then
again with gen specified.  The other thing is to call btrfs_read_buffer() on the
buffer we've found instead of dropping it and then calling read_tree_block().
This will keep us from doing yet another radix tree lookup for a buffer we've
already found.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
hifive-unleashed-5.1
Josef Bacik 2013-06-17 13:44:48 -04:00
parent fdf8e2ea3c
commit bdf7c00e8f
1 changed files with 21 additions and 28 deletions
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49
fs/btrfs/ctree.c
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@ -2359,35 +2359,28 @@ read_block_for_search(struct btrfs_trans_handle *trans,
tmp = btrfs_find_tree_block(root, blocknr, blocksize);
if (tmp) {
/* first we do an atomic uptodate check */
if (btrfs_buffer_uptodate(tmp, 0, 1) > 0) {
if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
/*
* we found an up to date block without
* sleeping, return
* right away
*/
*eb_ret = tmp;
return 0;
}
/* the pages were up to date, but we failed
* the generation number check. Do a full
* read for the generation number that is correct.
* We must do this without dropping locks so
* we can trust our generation number
*/
free_extent_buffer(tmp);
btrfs_set_path_blocking(p);
/* now we're allowed to do a blocking uptodate check */
tmp = read_tree_block(root, blocknr, blocksize, gen);
if (tmp && btrfs_buffer_uptodate(tmp, gen, 0) > 0) {
*eb_ret = tmp;
return 0;
}
free_extent_buffer(tmp);
btrfs_release_path(p);
return -EIO;
if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
*eb_ret = tmp;
return 0;
}
/* the pages were up to date, but we failed
* the generation number check. Do a full
* read for the generation number that is correct.
* We must do this without dropping locks so
* we can trust our generation number
*/
btrfs_set_path_blocking(p);
/* now we're allowed to do a blocking uptodate check */
ret = btrfs_read_buffer(tmp, gen);
if (!ret) {
*eb_ret = tmp;
return 0;
}
free_extent_buffer(tmp);
btrfs_release_path(p);
return -EIO;
}
/*