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dm: table detect io beyond device

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This patch fixes a panic on shrinking a DM device if there is
outstanding I/O to the part of the device that is being removed.
(Normally this doesn't happen - a filesystem would be resized first,
for example.)

The bug is that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer.  It may fail if a bio arrives from the
block layer but its target sector is no longer included in the DM
btree.

This patch appends an empty entry to table->targets[] which will
be returned by a lookup beyond the end of the device.

After calling dm_table_find_target(), __clone_and_map() and target_message()
check for this condition using
dm_target_is_valid().

Sample test script to trigger oops:
This commit is contained in:
Jun'ichi Nomura
2007-12-13 14:15:25 +00:00
committed by Alasdair G Kergon
parent fbdcf18df7
commit 512875bd96
4 changed files with 32 additions and 14 deletions
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7
drivers/md/dm-table.c
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@ -189,8 +189,10 @@ static int alloc_targets(struct dm_table *t, unsigned int num)
/*
* Allocate both the target array and offset array at once.
* Append an empty entry to catch sectors beyond the end of
* the device.
*/
n_highs = (sector_t *) dm_vcalloc(num, sizeof(struct dm_target) +
n_highs = (sector_t *) dm_vcalloc(num + 1, sizeof(struct dm_target) +
sizeof(sector_t));
if (!n_highs)
return -ENOMEM;
@ -867,6 +869,9 @@ struct dm_target *dm_table_get_target(struct dm_table *t, unsigned int index)
/*
* Search the btree for the correct target.
*
* Caller should check returned pointer with dm_target_is_valid()
* to trap I/O beyond end of device.
*/
struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
{