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f2fs: fix a race condition in next_free_nid

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The nm_i->fcnt checking is executed before spin_lock, so if another
thread delete the last free_nid from the list, the wrong nid may be
gotten.  So fix the race condition by moving the nm_i->fnct checking
into spin_lock.

Signed-off-by: Huang, Ying <ying.huang@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Huang Ying 2014-09-12 19:21:11 +08:00 committed by Jaegeuk Kim
parent 7704182387
commit c6e489305e
1 changed files with 4 additions and 2 deletions
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6
fs/f2fs/node.h
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@ -115,9 +115,11 @@ static inline int next_free_nid(struct f2fs_sb_info *sbi, nid_t *nid)
struct f2fs_nm_info *nm_i = NM_I(sbi);
struct free_nid *fnid;
if (nm_i->fcnt <= 0)
return -1;
spin_lock(&nm_i->free_nid_list_lock);
if (nm_i->fcnt <= 0) {
spin_unlock(&nm_i->free_nid_list_lock);
return -1;
}
fnid = list_entry(nm_i->free_nid_list.next, struct free_nid, list);
*nid = fnid->nid;
spin_unlock(&nm_i->free_nid_list_lock);