Commit 7132de74 authored Jul 10, 2011 by Maxim Patlasov Committed by Theodore Ts'o Jul 10, 2011

ext4: fix i_blocks/quota accounting when extent insertion fails



The current implementation of ext4_free_blocks() always calls
dquot_free_block This looks quite sensible in the most cases: blocks
to be freed are associated with inode and were accounted in quota and
i_blocks some time ago.

However, there is a case when blocks to free were not accounted by the
time calling ext4_free_blocks() yet:

1. delalloc is on, write_begin pre-allocated some space in quota
2. write-back happens, ext4 allocates some blocks in ext4_ext_map_blocks()
3. then ext4_ext_map_blocks() gets an error (e.g.  ENOSPC) from
   ext4_ext_insert_extent() and calls ext4_free_blocks().

In this scenario, ext4_free_blocks() calls dquot_free_block() who, in
turn, decrements i_blocks for blocks which were not accounted yet (due
to delalloc) After clean umount, e2fsck reports something like:

> Inode 21, i_blocks is 5080, should be 5128.  Fix<y>?
because i_blocks was erroneously decremented as explained above.

The patch fixes the problem by passing the new flag
EXT4_FREE_BLOCKS_NO_QUOT_UPDATE to ext4_free_blocks(), to request
that the dquot_free_block() call be skipped.

Signed-off-by: Maxim Patlasov <maxim.patlasov@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

parent 275d3ba6

fs/ext4/ext4.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -526,6 +526,7 @@ struct ext4_new_group_data {
		#define EXT4_FREE_BLOCKS_METADATA 0x0001
		#define EXT4_FREE_BLOCKS_FORGET 0x0002
		#define EXT4_FREE_BLOCKS_VALIDATED 0x0004
		#define EXT4_FREE_BLOCKS_NO_QUOT_UPDATE 0x0008

		/*
		* ioctl commands

fs/ext4/extents.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -3565,12 +3565,14 @@ int ext4_ext_map_blocks(handle_t handle, struct inode inode,

		err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
		if (err) {
		int fb_flags = flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE ?
		EXT4_FREE_BLOCKS_NO_QUOT_UPDATE : 0;
		/* free data blocks we just allocated */
		/* not a good idea to call discard here directly,
		* but otherwise we'd need to call it every free() */
		ext4_discard_preallocations(inode);
		ext4_free_blocks(handle, inode, NULL, ext4_ext_pblock(&newex),
		ext4_ext_get_actual_len(&newex), 0);
		ext4_ext_get_actual_len(&newex), fb_flags);
		goto out2;
		}

fs/ext4/mballoc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -4637,7 +4637,7 @@ do_more:
		}
		ext4_mark_super_dirty(sb);
		error_return:
		if (freed)
		if (freed && !(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
		dquot_free_block(inode, freed);
		brelse(bitmap_bh);
		ext4_std_error(sb, err);

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