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kill-the-BKL/reiserfs: release the write lock inside get_neighbors()

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get_neighbors() is used to get the left and/or right blocks
against a given one in order to balance a tree.

sb_bread() is used to read the buffer of these neighors blocks and
while it waits for this operation, it might sleep.

The bkl was released at this point, and then we can also release
the write lock before calling sb_bread().

This is safe because if the filesystem is changed after this
lock release, the function returns REPEAT_SEARCH (aka SCHEDULE_OCCURRED
in the function header comments) in order to repeat the neighbhor
research.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker 2009-05-01 01:10:52 +02:00
parent 5e69e3a449
commit 148d3504c1
1 changed files with 4 additions and 0 deletions
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4
fs/reiserfs/fix_node.c
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@ -1971,7 +1971,9 @@ static int get_neighbors(struct tree_balance *tb, int h)
tb->FL[h]) ? tb->lkey[h] : B_NR_ITEMS(tb->
FL[h]);
son_number = B_N_CHILD_NUM(tb->FL[h], child_position);
reiserfs_write_unlock(sb);
bh = sb_bread(sb, son_number);
reiserfs_write_lock(sb);
if (!bh)
return IO_ERROR;
if (FILESYSTEM_CHANGED_TB(tb)) {
@ -2009,7 +2011,9 @@ static int get_neighbors(struct tree_balance *tb, int h)
child_position =
(bh == tb->FR[h]) ? tb->rkey[h] + 1 : 0;
son_number = B_N_CHILD_NUM(tb->FR[h], child_position);
reiserfs_write_unlock(sb);
bh = sb_bread(sb, son_number);
reiserfs_write_lock(sb);
if (!bh)
return IO_ERROR;
if (FILESYSTEM_CHANGED_TB(tb)) {