/**
* run_gc - run garbage collector.
* @c: UBIFS file-system description object
*
* This function runs garbage collector to make some more free space. Returns
* zero if a free LEB has been produced, %-EAGAIN if commit is required, and a
* negative error code in case of failure.
*/
static int run_gc(struct ubifs_info *c)
{
int err, lnum;
/* Make some free space by garbage-collecting dirty space */
down_read(&c->commit_sem);
lnum = ubifs_garbage_collect(c, 1);
up_read(&c->commit_sem);
if (lnum < 0)
return lnum;
/* GC freed one LEB, return it to lprops */
dbg_budg("GC freed LEB %d", lnum);
err = ubifs_return_leb(c, lnum);
if (err)
return err;
return 0;
}
/**
* reserve_space - reserve space in the journal.
* @c: UBIFS file-system description object
* @jhead: journal head number
* @len: node length
*
* This function reserves space in journal head @head. If the reservation
* succeeded, the journal head stays locked and later has to be unlocked using
* 'release_head()'. 'write_node()' and 'write_head()' functions also unlock
* it. Returns zero in case of success, %-EAGAIN if commit has to be done, and
* other negative error codes in case of other failures.
*/
static int reserve_space(struct ubifs_info *c, int jhead, int len)
{
int err = 0, err1, retries = 0, avail, lnum, offs, free, squeeze;
struct ubifs_wbuf *wbuf = &c->jheads[jhead].wbuf;
/*
* Typically, the base head has smaller nodes written to it, so it is
* better to try to allocate space at the ends of eraseblocks. This is
* what the squeeze parameter does.
*/
squeeze = (jhead == BASEHD);
again:
mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
avail = c->leb_size - wbuf->offs - wbuf->used;
if (wbuf->lnum != -1 && avail >= len)
return 0;
/*
* Write buffer wasn't seek'ed or there is no enough space - look for an
* LEB with some empty space.
*/
lnum = ubifs_find_free_space(c, len, &free, squeeze);
if (lnum >= 0) {
/* Found an LEB, add it to the journal head */
offs = c->leb_size - free;
err = ubifs_add_bud_to_log(c, jhead, lnum, offs);
if (err)
goto out_return;
/* A new bud was successfully allocated and added to the log */
goto out;
}
err = lnum;
if (err != -ENOSPC)
goto out_unlock;
/*
* No free space, we have to run garbage collector to make
* some. But the write-buffer mutex has to be unlocked because
* GC have to sync write buffers, which may lead a deadlock.
*/
dbg_jrn("no free space jhead %d, run GC", jhead);
mutex_unlock(&wbuf->io_mutex);
lnum = ubifs_garbage_collect(c, 0);
if (lnum < 0) {
err = lnum;
if (err != -ENOSPC)
return err;
/*
* GC could not make a free LEB. But someone else may
* have allocated new bud for this journal head,
* because we dropped the 'io_mutex', so try once
* again.
*/
dbg_jrn("GC couldn't make a free LEB for jhead %d", jhead);
if (retries++ < 2) {
dbg_jrn("retry (%d)", retries);
goto again;
}
dbg_jrn("return -ENOSPC");
return err;
}
mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
dbg_jrn("got LEB %d for jhead %d", lnum, jhead);
avail = c->leb_size - wbuf->offs - wbuf->used;
if (wbuf->lnum != -1 && avail >= len) {
/*
* Someone else has switched the journal head and we have
* enough space now. This happens when more then one process is
* trying to write to the same journal head at the same time.
*/
dbg_jrn("return LEB %d back, already have LEB %d:%d",
lnum, wbuf->lnum, wbuf->offs + wbuf->used);
err = ubifs_return_leb(c, lnum);
if (err)
goto out_unlock;
return 0;
}
err = ubifs_add_bud_to_log(c, jhead, lnum, 0);
if (err)
goto out_return;
offs = 0;
out:
err = ubifs_wbuf_seek_nolock(wbuf, lnum, offs, UBI_SHORTTERM);
if (err)
goto out_unlock;
return 0;
out_unlock:
mutex_unlock(&wbuf->io_mutex);
return err;
out_return:
/* An error occurred and the LEB has to be returned to lprops */
ubifs_assert(err < 0);
err1 = ubifs_return_leb(c, lnum);
if (err1 && err == -EAGAIN)
/*
* Return original error code 'err' only if it is not
* '-EAGAIN', which is not really an error. Otherwise, return
* the error code of 'ubifs_return_leb()'.
*/
err = err1;
mutex_unlock(&wbuf->io_mutex);
return err;
}
