tmpfs: fix off-by-one in max_blocks checks

If you fill up a tmpfs, df was showing tmpfs 460800 - - - /tmp because of an off-by-one in the max_blocks checks. Fix it so df shows tmpfs 460800 460800 0 100% /tmp Signed-off-by: Hugh Dickins <[email protected]> Cc: Tim Chen <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
diverger · Apr 14, 2011 · fc5da22 · fc5da22
1 parent d00ebea
commit fc5da22
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/mm/shmem.c b/mm/shmem.c
@@ -421,7 +421,8 @@ static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long
 		 * a waste to allocate index if we cannot allocate data.
 		 */
 		if (sbinfo->max_blocks) {
-			if (percpu_counter_compare(&sbinfo->used_blocks, (sbinfo->max_blocks - 1)) > 0)
+			if (percpu_counter_compare(&sbinfo->used_blocks,
+						sbinfo->max_blocks - 1) >= 0)
 				return ERR_PTR(-ENOSPC);
 			percpu_counter_inc(&sbinfo->used_blocks);
 			spin_lock(&inode->i_lock);
@@ -1397,7 +1398,8 @@ static int shmem_getpage(struct inode *inode, unsigned long idx,
 		shmem_swp_unmap(entry);
 		sbinfo = SHMEM_SB(inode->i_sb);
 		if (sbinfo->max_blocks) {
-			if ((percpu_counter_compare(&sbinfo->used_blocks, sbinfo->max_blocks) > 0) ||
+			if (percpu_counter_compare(&sbinfo->used_blocks,
+						sbinfo->max_blocks) >= 0 ||
 			    shmem_acct_block(info->flags)) {
 				spin_unlock(&info->lock);
 				error = -ENOSPC;