Hi Bryn,
I'll also get the version on kernel.org updated - thanks for catching
this!
thanks very much for that quick patch - it works as expected and the kernel
oops went away!
since i want to use dm-loop for having a large number of loop-devices, i did
some more "hardcore testing". ;)
so, i wrote a little test script which created a lot of dummy-files and
turning them into a dm-loop target.
this worked very well - must have been around 3000 loop-targets when i got
this one:
# device-mapper: reload ioctl failed: not enough memory available
and in dmesg:
Jan 22 22:42:06 localhost device-mapper: loop: Finalized extent map of 56
bytes, 2 entries.
Jan 22 22:42:08 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:08 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:09 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:09 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:10 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:10 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:10 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:10 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:10 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:10 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:12 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:13 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:13 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:13 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:13 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
Jan 22 22:42:13 localhost dmlosetup: page allocation failure. order:4,
mode:0xd0
Jan 22 22:42:13 localhost [<c015e1a2>] __alloc_pages+0x272/0x2f0
this was on a system with 256 MB of ram.
i assume, that i ran out of some kernel-buffer memory.
ok, not a real problem for me since i don`t expect having that much number
of iso images on my cd-roms server to be loopback mounted, but - anyway -
could you probably give a comment on this ?
is this some "natural limitation" due to dm-loop or device mapper consuming
kernel-memory, or could this be another bug ?
regards
roland
----- Original Message -----
From: "Bryn M. Reeves" <breeves@xxxxxxxxxx>
To: <devzero@xxxxxx>
Cc: <agk@xxxxxxxxxx>; <dm-devel@xxxxxxxxxx>
Sent: Monday, January 22, 2007 11:00 AM
Subject: Re: bug in dm-loop? - was:Re: Re: device mapper integrated loops -
and one more year !
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
devzero@xxxxxx wrote:
i was doing some testing of dm-loop with latest dmsetup on a 2.6.20-rc5
system.
i did some basic test, which seems to work ok.
i can now map a file to become /dev/mapper/loop0
dmlosetup loop0 test.img
-> device-mapper: loop: Finalized extent map of 1232 bytes, 44 entries.
root@localhost ~ # ls -la /dev/mapper/loop0
brw------- 1 root root 252, 0 21. Jan 17:25 /dev/mapper/loop0
Great! Am glad this much is working for you!
while fiddling around a little bit, i accidentally tried to map that file
a second time - anyway, i would expect this is quite ok and should work.
dmlosetup loop1 test.img
this bails out with the following error, leaving trace in dmesg:
device-mapper: loop: file is already in use:
/root/device-mapper/dmsetup/test.dat
BUG: unable to handle kernel NULL pointer dereference at virtual address
00000000
printing eip:
d097589c
*pde = 00000000
Oops: 0000 [#1]
The dm-loop target only allows a file to be mapped once. That said, it
should just return the error, not oops the kernel!
This is fixed in my CVS copy of this patch - I'm attaching a patch that
you can apply on top of the one that you already have that includes this
fix plus a couple of other minor fixes/enhancements.
I'll also get the version on kernel.org updated - thanks for catching
this!
after this, if i do
dmlosetup -d loop1
dmlosetup -d loop0
i cannot "rmmod dm-loop" , now telling me "device is in use", but it
isn`t !
so, this looks like a bug to me, leaving dm-loop in an inconsitent state.
Unfortunately, after an oops in a kernel module you're pretty much
forced to reboot - the kernel terminates the code path that caused the
fault, leaving a hanging reference count on the module.
furthermore, one question about naming conventions :
dmlosetup testloop1 test.dat
dmlosetup: Could not parse loop_device testloop1
Usage:
losetup [-d|-a] [-e encryption] [-o offset] [-f|loop_device] [file]
Couldn't process command line.
so, it`s mandatory that loop_device needs to begin with "loop...." !?
It is at the moment :) The current command line parameters try to be as
faithful as possible to the nomrmal losetup, where devices are normally
named as (/dev/)loopN. We can't exactly match that without disrupting
users of the regular loop driver though, so this should probably be
relaxed.
Thanks for testing!
Bryn.
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--------------------------------------------------------------------------------
--- drivers/md/dm-loop.c.rel 2007-01-22 09:45:04.000000000 +0000
+++ drivers/md/dm-loop.c 2007-01-22 09:45:10.000000000 +0000
@@ -22,7 +22,7 @@
#include "dm-bio-record.h"
#define DM_MSG_PREFIX "loop"
-#define LOOP_MAX_EXTENTS 1024
+#define LOOP_MAX_EXTENTS 2048
#define DMLOOP_READONLY 0x01
#define DMLOOP_SYNC 0x02
@@ -69,7 +69,7 @@ struct loop_c {
};
#ifdef CONFIG_DM_DEBUG
-static void dump_extent(struct extent *e)
+static void dump_extent(unsigned i, struct extent *e)
{
const char types[] = { 'f', 'd' };
@@ -81,8 +81,8 @@ static void dump_extent(struct extent *e
return;
}
- DMDEBUG("start: %8llu len: %4llu %4c.rstart: %8llu",
- e->start, e->len, types[e->type],
+ DMDEBUG(" [%u] start: %8llu len: %4llu %4c.rstart: %8llu",
+ i, e->start, e->len, types[e->type],
(sector_t)e->data );
}
@@ -97,7 +97,7 @@ static void dump_extent_map(struct exten
map->nr_extents, map->cur_extent);
for (i = 0; i < map->nr_extents; i++)
- dump_extent(DMLOOP_EXTENT(i));
+ dump_extent(i, DMLOOP_EXTENT(i));
}
#else /* CONFIG_DM_DEBUG */
@@ -228,16 +228,25 @@ reprobe:
continue;
}
+ if (nr_extents == LOOP_MAX_EXTENTS && probe_block < last_block){
+ DMERR("Loopfile contains more than LOOP_MAX_EXTENTS (%d) fragments\n",
+ LOOP_MAX_EXTENTS);
+ goto out_free;
+ }
+
map->nr_extents = nr_extents;
map->cur_extent = 0;
DMDEBUG("created initial extent map, finalizing.");
map = finalize_map(map);
+ if (!map)
+ return -ENOMEM;
+
+ //dump_extent_map(map);
DMINFO("Finalized extent map of %u bytes, %d entries.",
(map->nr_extents * sizeof(struct extent)),
map->nr_extents);
- dump_extent_map(map);
lc->blkbits = blkbits;
lc->map = map;
@@ -408,7 +417,7 @@ static struct file *loop_get_file(char *
{
struct file *filp;
struct inode *inode;
- int r;
+ int r = 0;
filp = filp_open(loop_path,
((*flags & DMLOOP_READONLY) ? O_RDONLY : O_RDWR) |
@@ -434,6 +443,7 @@ static struct file *loop_get_file(char *
if (IS_SWAPFILE(inode)) {
DMERR("file is already in use: %s", loop_path);
+ r = -EBUSY;
goto out;
}
@@ -461,7 +471,7 @@ static int loop_setup_size(struct loop_c
lc->size = i_size_read(inode);
lc->blkbits = inode->i_blkbits;
- if (lc->offset & (1 << lc->blkbits - 1)) {
+ if (lc->offset & ((1 << lc->blkbits) - 1)) {
DMERR("Backing file offset of %lld bytes not a multiple of "
"filesystem blocksize (%d)", lc->offset,
1 << lc->blkbits);
@@ -565,8 +575,11 @@ static int loop_ctr(struct dm_target *ti
goto out_putf;
r = setup_loop_extents(lc);
- if (r) {
- ti->error = "Could not create extent map";
+ if (r == -EINVAL) {
+ ti->error = "Could not create extent map - invalid argument";
+ goto out_putf;
+ } else if (r == -ENOMEM) {
+ ti->error = "Could not allocate extent map";
goto out_putf;
}
--
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