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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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24
drivers/md/dm.c
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@@ -672,13 +672,19 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
return clone;
}
static void __clone_and_map(struct clone_info *ci)
static int __clone_and_map(struct clone_info *ci)
{
struct bio *clone, *bio = ci->bio;
struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
struct dm_target *ti;
sector_t len = 0, max;
struct dm_target_io *tio;
ti = dm_table_find_target(ci->map, ci->sector);
if (!dm_target_is_valid(ti))
return -EIO;
max = max_io_len(ci->md, ci->sector, ti);
/*
* Allocate a target io object.
*/
@@ -736,6 +742,9 @@ static void __clone_and_map(struct clone_info *ci)
do {
if (offset) {
ti = dm_table_find_target(ci->map, ci->sector);
if (!dm_target_is_valid(ti))
return -EIO;
max = max_io_len(ci->md, ci->sector, ti);
tio = alloc_tio(ci->md);
@@ -759,6 +768,8 @@ static void __clone_and_map(struct clone_info *ci)
ci->idx++;
}
return 0;
}
/*
@@ -767,6 +778,7 @@ static void __clone_and_map(struct clone_info *ci)
static int __split_bio(struct mapped_device *md, struct bio *bio)
{
struct clone_info ci;
int error = 0;
ci.map = dm_get_table(md);
if (unlikely(!ci.map))
@@ -784,11 +796,11 @@ static int __split_bio(struct mapped_device *md, struct bio *bio)
ci.idx = bio->bi_idx;
start_io_acct(ci.io);
while (ci.sector_count)
__clone_and_map(&ci);
while (ci.sector_count && !error)
error = __clone_and_map(&ci);
/* drop the extra reference count */
dec_pending(ci.io, 0);
dec_pending(ci.io, error);
dm_table_put(ci.map);
return 0;