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UBIFS: split ubifs_rcvry_gc_commit 

Split the 'ubifs_rcvry_gc_commit()' function and introduce a 'grab_empty_leb()'
heler. This cleans 'ubifs_rcvry_gc_commit()' a little and makes it a bit less
of spagetti.

Also, add a commentary which explains why it is crucial to first search for an
empty LEB and then run commit.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit is contained in:
Artem Bityutskiy 2011-04-27 14:52:35 +03:00
parent ec06814265
commit 447442139c
1 changed files with 50 additions and 27 deletions
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77
fs/ubifs/recovery.c
View File

@ -1069,6 +1069,53 @@ int ubifs_clean_lebs(const struct ubifs_info *c, void *sbuf)
return 0;
}
/**
* grab_empty_leb - grab an empty LEB to use as GC LEB and run commit.
* @c: UBIFS file-system description object
*
* This is a helper function for 'ubifs_rcvry_gc_commit()' which grabs an empty
* LEB to be used as GC LEB (@c->gc_lnum), and then runs the commit. Returns
* zero in case of success and a negative error code in case of failure.
*/
static int grab_empty_leb(struct ubifs_info *c)
{
int lnum, err;
/*
* Note, it is very important to first search for an empty LEB and then
* run the commit, not vice-versa. The reason is that there might be
* only one empty LEB at the moment, the one which has been the
* @c->gc_lnum just before the power cut happened. During the regular
* UBIFS operation (not now) @c->gc_lnum is marked as "taken", so no
* one but GC can grab it. But at this moment this single empty LEB is
* not marked as taken, so if we run commit - what happens? Right, the
* commit will grab it and write the index there. Remember that the
* index always expands as long as there is free space, and it only
* starts consolidating when we run out of space.
*
* IOW, if we run commit now, we might not be able to find a free LEB
* after this.
*/
lnum = ubifs_find_free_leb_for_idx(c);
if (lnum < 0) {
dbg_err("could not find an empty LEB");
dbg_dump_lprops(c);
dbg_dump_budg(c, &c->bi);
return lnum;
}
/* Reset the index flag */
err = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
LPROPS_INDEX, 0);
if (err)
return err;
c->gc_lnum = lnum;
dbg_rcvry("found empty LEB %d, run commit", lnum);
return ubifs_run_commit(c);
}
/**
* ubifs_rcvry_gc_commit - recover the GC LEB number and run the commit.
* @c: UBIFS file-system description object
@ -1096,7 +1143,7 @@ int ubifs_rcvry_gc_commit(struct ubifs_info *c)
c->gc_lnum = -1;
if (wbuf->lnum == -1) {
dbg_rcvry("no GC head LEB");
goto find_free;
return grab_empty_leb(c);
}
/*
* See whether the used space in the dirtiest LEB fits in the GC head
@ -1104,7 +1151,7 @@ int ubifs_rcvry_gc_commit(struct ubifs_info *c)
*/
if (wbuf->offs == c->leb_size) {
dbg_rcvry("no room in GC head LEB");
goto find_free;
return grab_empty_leb(c);
}
err = ubifs_find_dirty_leb(c, &lp, wbuf->offs, 2);
if (err) {
@ -1121,7 +1168,7 @@ int ubifs_rcvry_gc_commit(struct ubifs_info *c)
*/
if (err == -ENOSPC) {
dbg_rcvry("could not find a dirty LEB");
goto find_free;
return grab_empty_leb(c);
}
return err;
}
@ -1167,30 +1214,6 @@ int ubifs_rcvry_gc_commit(struct ubifs_info *c)
return err;
dbg_rcvry("allocated LEB %d for GC", lnum);
return 0;
find_free:
/*
* There is no GC head LEB or the free space in the GC head LEB is too
* small, or there are not dirty LEBs. Allocate gc_lnum by calling
* 'ubifs_find_free_leb_for_idx()' so GC is not run.
*/
lnum = ubifs_find_free_leb_for_idx(c);
if (lnum < 0) {
dbg_err("could not find an empty LEB");
dbg_dump_lprops(c);
dbg_dump_budg(c, &c->bi);
return lnum;
}
/* And reset the index flag */
err = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
LPROPS_INDEX, 0);
if (err)
return err;
c->gc_lnum = lnum;
dbg_rcvry("allocated LEB %d for GC", lnum);
/* Run the commit */
dbg_rcvry("committing");
return ubifs_run_commit(c);
}
/**