ext4: fix ext4_discard_allocated_blocks() if we can't allocate the pa struct (86f0afd4) · Commits · 戴 / test

If there is a failure while allocating the preallocation structure, a number of blocks can end up getting marked in the in-memory buddy bitmap, and then not getting released. This can result in the following corruption getting reported by the kernel: EXT4-fs error (device sda3): ext4_mb_generate_buddy:758: group 1126, 12793 clusters in bitmap, 12729 in gd In that case, we need to release the blocks using mb_free_blocks(). Tested: fs smoke test; also demonstrated that with injected errors, the file system is no longer getting corrupted Google-Bug-Id: 16657874 Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org

fs/ext4/mballoc.c

+20 −1

Original line number	Diff line number	Diff line
		@@ -3217,8 +3217,27 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
		static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac)
		{
		struct ext4_prealloc_space *pa = ac->ac_pa;
		struct ext4_buddy e4b;
		int err;

		if (pa && pa->pa_type == MB_INODE_PA)
		if (pa == NULL) {
		err = ext4_mb_load_buddy(ac->ac_sb, ac->ac_f_ex.fe_group, &e4b);
		if (err) {
		/*
		* This should never happen since we pin the
		* pages in the ext4_allocation_context so
		* ext4_mb_load_buddy() should never fail.
		*/
		WARN(1, "mb_load_buddy failed (%d)", err);
		return;
		}
		ext4_lock_group(ac->ac_sb, ac->ac_f_ex.fe_group);
		mb_free_blocks(ac->ac_inode, &e4b, ac->ac_f_ex.fe_start,
		ac->ac_f_ex.fe_len);
		ext4_unlock_group(ac->ac_sb, ac->ac_f_ex.fe_group);
		return;
		}
		if (pa->pa_type == MB_INODE_PA)
		pa->pa_free += ac->ac_b_ex.fe_len;
		}

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