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kill-the-bkl/reiserfs: lock only once on reiserfs_get_block() 

reiserfs_get_block() is one of these sites where the write lock might
be acquired recursively.

It's a particular problem because this function is called very often.
It's a hot spot which needs to reschedule() periodically while converting
direct items to indirect ones because it can take some time.

Then if we are applying the write lock release/reacquire pattern on
schedule() here, it may not produce the desired effect since we may have
locked in more than one depth.

The solution is to use reiserfs_write_lock_once() which won't try
to reacquire the lock recursively. Then the lock will be *really*
released before schedule().

Also, we only release the lock if TIF_NEED_RESCHED is set to not
create wasteful numerous contentions.

[ Impact: fix a too long holded lock case in reiserfs_get_block() ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2009-05-07 23:48:44 +02:00
parent d663af807d
commit 26931309a4
1 changed files with 11 additions and 8 deletions
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19
fs/reiserfs/inode.c
View File

@ -605,6 +605,7 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
__le32 *item;
int done;
int fs_gen;
int lock_depth;
struct reiserfs_transaction_handle *th = NULL;
/* space reserved in transaction batch:
. 3 balancings in direct->indirect conversion
@ -620,11 +621,11 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
loff_t new_offset =
(((loff_t) block) << inode->i_sb->s_blocksize_bits) + 1;
reiserfs_write_lock(inode->i_sb);
lock_depth = reiserfs_write_lock_once(inode->i_sb);
version = get_inode_item_key_version(inode);
if (!file_capable(inode, block)) {
reiserfs_write_unlock(inode->i_sb);
reiserfs_write_unlock_once(inode->i_sb, lock_depth);
return -EFBIG;
}
@ -636,7 +637,7 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
/* find number of block-th logical block of the file */
ret = _get_block_create_0(inode, block, bh_result,
create | GET_BLOCK_READ_DIRECT);
reiserfs_write_unlock(inode->i_sb);
reiserfs_write_unlock_once(inode->i_sb, lock_depth);
return ret;
}
/*
@ -754,7 +755,7 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
if (!dangle && th)
retval = reiserfs_end_persistent_transaction(th);
reiserfs_write_unlock(inode->i_sb);
reiserfs_write_unlock_once(inode->i_sb, lock_depth);
/* the item was found, so new blocks were not added to the file
** there is no need to make sure the inode is updated with this
@ -1005,9 +1006,11 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
* long time. reschedule if needed and also release the write
* lock for others.
*/
reiserfs_write_unlock(inode->i_sb);
cond_resched();
reiserfs_write_lock(inode->i_sb);
if (need_resched()) {
reiserfs_write_unlock_once(inode->i_sb, lock_depth);
schedule();
lock_depth = reiserfs_write_lock_once(inode->i_sb);
}
retval = search_for_position_by_key(inode->i_sb, &key, &path);
if (retval == IO_ERROR) {
@ -1042,7 +1045,7 @@ int reiserfs_get_block(struct inode *inode, sector_t block,
retval = err;
}
reiserfs_write_unlock(inode->i_sb);
reiserfs_write_unlock_once(inode->i_sb, lock_depth);
reiserfs_check_path(&path);
return retval;
}