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ext4: Properly initialize the buffer_head state

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These struct buffer_heads are allocated on the stack (and hence are
initialized with stack garbage).  They are only used to call a
get_blocks() function, so that's mostly OK, but b_state must be
initialized to be 0 so we don't have any unexpected BH_* flags set by
accident, such as BH_Unwritten or BH_Delay.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Aneesh Kumar K.V
2009-05-13 15:13:42 -04:00
committed by Theodore Ts'o
parent 9fa7eb283c
commit 79ffab3439
3 changed files with 19 additions and 3 deletions
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15
fs/ext4/inode.c
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@@ -2055,7 +2055,20 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
if ((mpd->b_state & (1 << BH_Mapped)) &&
!(mpd->b_state & (1 << BH_Delay)))
return 0;
new.b_state = mpd->b_state;
/*
* We need to make sure the BH_Delay flag is passed down to
* ext4_da_get_block_write(), since it calls
* ext4_get_blocks_wrap() with the EXT4_DELALLOC_RSVED flag.
* This flag causes ext4_get_blocks_wrap() to call
* ext4_da_update_reserve_space() if the passed buffer head
* has the BH_Delay flag set. In the future, once we clean up
* the interfaces to ext4_get_blocks_wrap(), we should pass in
* a separate flag which requests that the delayed allocation
* statistics should be updated, instead of depending on the
* state information getting passed down via the map_bh's
* state bitmasks plus the magic EXT4_DELALLOC_RSVED flag.
*/
new.b_state = mpd->b_state & (1 << BH_Delay);
new.b_blocknr = 0;
new.b_size = mpd->b_size;
next = mpd->b_blocknr;