2013-05-08 (수), 14:24 +0800, Haicheng Li: > On Tue, May 07, 2013 at 07:33:59PM +0900, Jaegeuk Kim wrote: > > 2013-05-06 (월), 23:15 +0800, Haicheng Li: > > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > > > index 1fe3fe2..3136224 100644 > > > --- a/fs/f2fs/node.c > > > +++ b/fs/f2fs/node.c > > > @@ -1342,6 +1342,8 @@ static void build_free_nids(struct f2fs_sb_info *sbi) > > > if (nid >= nm_i->max_nid) > > > nid = 0; > > > > > > + if (nm_i->fcnt > 2 * MAX_FREE_NIDS) > > > + break; > > > > Could you explain when this can happen? > > I'm thinking of this possible scenario: > > as we don't hold any spinlock to protect the context, add_free_nid() could be > called by other thread anytime, e.g. by the gc_thread_func() in background. The gc_thread_func() is not a proper example here though, the buid_free_nids() is covered by nm_i->build_lock, so build_free_nids is entered only one at a time. In addtion, build_free_nids starts with checking if (nm_i->fcnt > NAT_ENTRY_PER_BLOCK) in order not to be conducted repeatedely. > > then nm_i->fcnt could be increased as 2 * MAX_FREE_NIDS while i < FREE_NID_PAGES. > Anything I misconsidered? Apart from the correctness of this behavior, I'm not sure why we should strictly manage this threshold value. Should we really need to do this? > > > IMO, this is an unnecessary condition check, since the below condition > > that includes FREE_NID_PAGES already limits the number of free nids. > > Thanks, > > hmm, the pros is that this check may possibly avoid some (< 4) unnecessary while-loop, > the cons is that too many checks of (nm_i->fcnt > 2 * MAX_FREE_NIDS) > would make the code looking messy and fragmentary... > > > > if (i++ == FREE_NID_PAGES) > > > break; > > > } > > > > -- > > Jaegeuk Kim > > Samsung > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Jaegeuk Kim Samsung
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