* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: > 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 ] This should also be safe because under the BKL we _already_ dropped the lock when sb_bread() blocked (which it really would in the normal case). There's one special case to consider though: sb_read() maps to __bread() which can return without sleeping if the bh is already uptodate. So if the filesystem _knows_ that the bh is already uptodate and holds a reference to it (this is common pattern in filesystems), it can have a locking assumption on that. No such assumption seems to be present here though. Ingo -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
