New: Accraid / aptec / Microsemi / ext4 / larger then 16TB

https://bugzilla.kernel.org/show_bug.cgi?id=207367

Bug ID: 207367
Summary: Accraid / aptec / Microsemi / ext4 / larger then 16TB
Product: File System
Version: 2.5
Kernel Version: 5.7_rcx
Hardware: Intel
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
Assignee: [email protected]
Reporter: [email protected]
Regression: No

Can mout volume over 16TB ( 34TB ,40TB )

with controler accraid / hardware rais

btrfs runs , etx4 not

14 TB raid can mount

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

Christian Kujau ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #1 from Christian Kujau ([email protected]) ---
Walter, please provide way more information here: describe the setup, provide
the exact error messages, did it work before, what changed that it doesn't work
anymore, etc. Maybe report the bug to the ext4 mailing list before logging a
tracking bug here. See also: [How to report Linux kernel bugs](https://www.kernel.org/doc/html/latest/admin-guide/reporting-bugs.html#how-to-report-linux-kernel-bugs)

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #2 from walter59 ([email protected]) --- hi ,

bug on two servers , using kernel 5.6x no problems

with kernel 5.7 only volumes under 16TB can be mount.

testet also clear volume new partion , an make fs ext4 .

new created vloume dont mount . use btrfs not problem.

return to kernel 5.6 , there are no problems.

so me can say there are no hardware problems or lowlevel drivers--- btrfs works --- only ext4 not

You are receiving this mail because:
You are watching the assignee of the bug.

While this bug report is still missing details, I was able to reproduce this issue. Contrary to the subject line, it is not hardware related at all.

Linux 5.5 (Debian), creating a 17 TB sparse device (4 GB backing device):

 $ echo "0 36507222016 zero" | dmsetup create zero0
 $ echo "0 36507222016 snapshot /dev/mapper/zero0 /dev/vdb p 128" | \
   dmsetup create sparse0

 $ mkfs.ext4 -F /dev/mapper/sparse0
 Creating filesystem with 4563402752 4k blocks and 285212672 inodes
 Creating journal (262144 blocks): done

 $ mount -t ext4 /dev/mapper/sparse0 /mnt/disk/
 $ df -h /mnt/disk/
 Filesystem      Size  Used Avail Use% Mounted on
 /dev/mapper/sparse0   17T   24K   17T   1% /mnt/disk

The same fails on 5.7-rc2 (vanilla) with:

------------[ cut here ]------------
would truncate bmap result
WARNING: CPU: 0 PID: 640 at fs/iomap/fiemap.c:121 
iomap_bmap_actor+0x3a/0x40
Modules linked in: dm_zero 9p xhci_pci xhci_hcd virtio_balloon 
9pnet_virtio loop fuse sunrpc
CPU: 0 PID: 640 Comm: mount Not tainted 5.7.0-rc2 #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 
04/01/2014
RIP: 0010:iomap_bmap_actor+0x3a/0x40
Code: 70 08 0f b6 8f 86 00 00 00 49 03 30 48 d3 ee 48 81 fe ff ff ff 7f 77 
06 48 89 30 31 c0 c3 48 c7 c7 fa 71 56 a9 e8 04 f7 ea ff <0f> 0b 31 c0 c3 
cc 41 54 55 53 48 83 ec 08 48 8b 47 48 48 89 34 24
RSP: 0018:ffffb8fd8090bb80 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffffa9424bb0 RCX: 0000000000000000
RDX: ffff996abbc1ed40 RSI: ffff996abbc180c8 RDI: ffff996abbc180c8
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000277
R10: 0000000000000774 R11: ffffb8fd8090ba35 R12: 0000000000000000
R13: ffff996aafc6e9b8 R14: ffffb8fd8090bc70 R15: 0000000000001000
FS:  00007efc34fafc80(0000) GS:ffff996abbc00000(0000) 
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efc352f29a0 CR3: 000000016e074003 CR4: 0000000000360eb0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 iomap_apply+0xf4/0x1a0
 ? iomap_fiemap_actor+0x90/0x90
 iomap_bmap+0x70/0x90
 ? iomap_fiemap_actor+0x90/0x90
 bmap+0x1d/0x30
 jbd2_journal_init_inode+0x2b/0xe0
 ext4_fill_super+0x29c4/0x3300
 ? mount_bdev+0x171/0x1a0
 ? ext4_calculate_overhead+0x480/0x480
 mount_bdev+0x171/0x1a0
 ? ext4_calculate_overhead+0x480/0x480
 legacy_get_tree+0x22/0x40
 vfs_get_tree+0x1b/0x80
 ? ns_capable_common+0x29/0x50
 do_mount+0x713/0x9f0
 ? memdup_user+0x49/0x90
 __x64_sys_mount+0x89/0xc0
 do_syscall_64+0x60/0x3b0
 ? do_page_fault+0x243/0x4bb
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7efc351c7e1a
Code: 48 8b 0d 79 e0 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 

00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 46 e0 0b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe6e5bce18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000055d888f5cb00 RCX: 00007efc351c7e1a
RDX: 000055d888f5cd10 RSI: 000055d888f5ea30 RDI: 000055d888f5cd30
RBP: 00007efc35318204 R08: 0000000000000000 R09: 000055d888f5ee00
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000055d888f5cd30 R15: 000055d888f5cd10

---[ end trace 513dea1cc94aa289 ]---

jbd2_journal_init_inode: Cannot locate journal superblock EXT4-fs (dm-1): Could not load journal inode

HTH,
Christian.

BOFH excuse #306:

CPU-angle has to be adjusted because of vibrations coming from the nearby road

A git bisect run pointed to:

-------------------------------------------------------------------------
commit ac58e4fb03f9d111d733a4ad379d06eef3a24705
Author: Ritesh Harjani <[email protected]>
Date: Fri Feb 28 14:56:56 2020 +0530

ext4: move ext4 bmap to use iomap infrastructure

ext4_iomap_begin is already implemented which provides ext4_map_blocks, so just move the API from generic_block_bmap to iomap_bmap for iomap conversion.
--------------------------------------------------------------------------

With only this commit reverted, v5.7-rc2 is able mount (and access) large ext4 filesystems again.

Thanks to Walter Moeller for reporting this in the first place.

HTH,
Christian.

BOFH excuse #29:

It works the way the Wang did, what's the problem

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #3 from Christian Kujau ([email protected]) ---

While this bug report is still missing details, I was able to reproduce this issue. Contrary to the subject line, it is not hardware related at all.

Linux 5.5 (Debian), creating a 17 TB sparse device (4 GB backing device):

 $ echo "0 36507222016 zero" | dmsetup create zero0
 $ echo "0 36507222016 snapshot /dev/mapper/zero0 /dev/vdb p 128" | \
   dmsetup create sparse0

 $ mkfs.ext4 -F /dev/mapper/sparse0
 Creating filesystem with 4563402752 4k blocks and 285212672 inodes
 Creating journal (262144 blocks): done

 $ mount -t ext4 /dev/mapper/sparse0 /mnt/disk/
 $ df -h /mnt/disk/
 Filesystem      Size  Used Avail Use% Mounted on
 /dev/mapper/sparse0   17T   24K   17T   1% /mnt/disk

The same fails on 5.7-rc2 (vanilla) with:

------------[ cut here ]------------
would truncate bmap result
WARNING: CPU: 0 PID: 640 at fs/iomap/fiemap.c:121 
iomap_bmap_actor+0x3a/0x40
Modules linked in: dm_zero 9p xhci_pci xhci_hcd virtio_balloon 
9pnet_virtio loop fuse sunrpc
CPU: 0 PID: 640 Comm: mount Not tainted 5.7.0-rc2 #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 
04/01/2014
RIP: 0010:iomap_bmap_actor+0x3a/0x40
Code: 70 08 0f b6 8f 86 00 00 00 49 03 30 48 d3 ee 48 81 fe ff ff ff 7f 77 
06 48 89 30 31 c0 c3 48 c7 c7 fa 71 56 a9 e8 04 f7 ea ff <0f> 0b 31 c0 c3 
cc 41 54 55 53 48 83 ec 08 48 8b 47 48 48 89 34 24
RSP: 0018:ffffb8fd8090bb80 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffffa9424bb0 RCX: 0000000000000000
RDX: ffff996abbc1ed40 RSI: ffff996abbc180c8 RDI: ffff996abbc180c8
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000277
R10: 0000000000000774 R11: ffffb8fd8090ba35 R12: 0000000000000000
R13: ffff996aafc6e9b8 R14: ffffb8fd8090bc70 R15: 0000000000001000
FS:  00007efc34fafc80(0000) GS:ffff996abbc00000(0000) 
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efc352f29a0 CR3: 000000016e074003 CR4: 0000000000360eb0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 iomap_apply+0xf4/0x1a0
 ? iomap_fiemap_actor+0x90/0x90
 iomap_bmap+0x70/0x90
 ? iomap_fiemap_actor+0x90/0x90
 bmap+0x1d/0x30
 jbd2_journal_init_inode+0x2b/0xe0
 ext4_fill_super+0x29c4/0x3300
 ? mount_bdev+0x171/0x1a0
 ? ext4_calculate_overhead+0x480/0x480
 mount_bdev+0x171/0x1a0
 ? ext4_calculate_overhead+0x480/0x480
 legacy_get_tree+0x22/0x40
 vfs_get_tree+0x1b/0x80
 ? ns_capable_common+0x29/0x50
 do_mount+0x713/0x9f0
 ? memdup_user+0x49/0x90
 __x64_sys_mount+0x89/0xc0
 do_syscall_64+0x60/0x3b0
 ? do_page_fault+0x243/0x4bb
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7efc351c7e1a
Code: 48 8b 0d 79 e0 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 

00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 46 e0 0b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe6e5bce18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000055d888f5cb00 RCX: 00007efc351c7e1a
RDX: 000055d888f5cd10 RSI: 000055d888f5ea30 RDI: 000055d888f5cd30
RBP: 00007efc35318204 R08: 0000000000000000 R09: 000055d888f5ee00
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000055d888f5cd30 R15: 000055d888f5cd10

---[ end trace 513dea1cc94aa289 ]---

jbd2_journal_init_inode: Cannot locate journal superblock EXT4-fs (dm-1): Could not load journal inode

HTH,
Christian.

You are receiving this mail because:
You are watching the assignee of the bug.

Hello All,

Sorry about not seeing this through in the first place.

So the problem really is that the iomap_bmap() API gives WARNING and does't return the physical block address in case if the addr is > INT_MAX. (I guess this could be mostly since the ioctl_fibmap() passes a user integer pointer and users of iomap_bmap() may mostly be coming from ioctl path till now).

FYI - I do see that bmap() is also used by below APIs/subsystem. Not sure if any of subsystems mentioned below may still fail later if the underlying FS moved to iomap_bmap() interface or for any existing callers of iomap_bmap() :-

1. mm/page-io.c (generic_swapfile_activate() func)
2. fs/cachefiles/rdwr.c
3. fs/ecryptfs/mmap.c
4. fs/jbd2/journal.c

But the changes done in ext4 to move to iomap_bmap() interface resulted in this issue since jbd2 tries to find the block mapping of on disk journal inode of ext4 and on a larger filesystem this may fail given the design of iomap_bmap() to not return addr if > INT_MAX.

So as I see it there are 3 options from here. Wanted to put this on mailing list for discussion.

1. Make changes in iomap_bmap() to return the block address mapping. But I still would like to mention that iomap designers may not agree with this here Since the direction in general is to get rid of bmap() interface anyways.

2. Revert the patch series of "bmap & fiemap to move to iomap interface" (why fiemap too? - since if we decide to revert bmap anyways, then we better fix the performance numbers report too coming from fiemap. Also due to 3rd option below since if iomap_bmap() is not changed, then we better keep both of this interface as is until we get the solution like 3 below.)

3. To move to a new internal API like fiemap. But we need to change fiemap in a way that it should also be allowed to used by internal kernel APIs. Since as of now fiemap_extent struct is assumed to be a user pointer.

(But the 3rd option as I see, won't be possible given the time frame to fix this issue. Also note if we decide to revert the changes, then the long term path would be to work on making fiemap used by internal kernel APIs too).

struct fiemap_extent_info {
unsigned int fi_flags; /* Flags as passed from user */
unsigned int fi_extents_mapped; /* Number of mapped extents */
unsigned int fi_extents_max; /* Size of fiemap_extent array */
struct fiemap_extent __user *fi_extents_start; /* Start of
fiemap_extent array */
};

-ritesh

No, it's because bmap is fundamentally broken when it comes to block ranges > INT_MAX. The filesystem in question is a >16TB filesystem, so the block range for that filesystem is >32bits, and hence usage of bmap in the jbd2 code is broken.

Basically, jbd2 needs fixing to be able to map blocks that are at higher offsets than bmap can actually report.

Filesystems using iomap infrastructure should be providing aops->swap_activate() to map swapfile extents via iomap_swapfile_activate() (e.g. see xfs_iomap_swapfile_activate()), not using generic_swapfile_activate().

Known problem, work being done to stop using bmap() here

Just a wrapper to pass ->bmap calls through to the lower layer.

Broken on filesystems where the journal file might be placed beyond a 32 bit block number, iomap_bmap() just makes that obvious. Needs fixing.

You also missed f2fs copy-n-waste using it for internal swapfile mapping:

/* Copied from generic_swapfile_activate() to check any holes */

That needs fixing, too.

And you missed the MD bitmap code uses bmap() to map it's bitmap storage file, which means that is broken is the bitmap file is on a filesystem/block device > 16TB, too...

Nope. bmap() is broken. Get rid of it.

The use of bmap was broken prior to this conversion - shooting the messenger doesn't fix the problem. Get rid of bmap().

Fiemap cannot be used this way. It's a diagnostic interface that provides no guarantee of coherency or atomicity, so you can't use it in this way in userspace or the kernel.

IMO, the correct thing to do is for the caller to supply jbd with a block mapping callback. i.e. jbd2_journal_init_inode() gets called from both ext4 and ocfs2 with a callback that does the block mapping for that specific filesystem. Indeed, jbd2 will need to cache that callback, because it needs to call it to map journal blocks when committing transactions....

Cheers,

Dave.

Dave Chinner
[email protected]

Hello,

IIUC, what you meant is that bmap in general as a interface is broken because if some user tries to call this interface via an ioctl for a file which is placed beyond 32 bits on a filesystem, then it truncates the results (basically gives us wrong results). Also this means as a user interface this was not designed properly keeping the block addresses range in mind (that someday it will extent beyong 32 bits).

Due to above reason, we don't make iomap_bmap() API return the u64 addr in it's argument, even though it is capable of doing that. Is that the reason?
And this is because since the overall interface from userspace side is broken and so we want to get rid of that.

So what I would still like to understand is- that bmap() internal kernel function can definitely handle the sector_t block addresses, right? Isn't the bmap() kernel function was designed for this purpose in mind, to help internal kernel callers to provide with u64 block addresses?

But for e.g. here, when jbd2 calls for bmap(), it will eventually call for ext4_bmap() -> iomap_bmap(). Now even though this chain is capable of handling u64 addresses, but it's the iomap_bmap() which doesn't provide this. So the question simply is why?

Sorry about my query here, it is to only to understand more about this and to not force in anyway to change iomap_bmap() to just get this working.

Sure.

hmm. Yes, I guess even with FIEMAP_FLAG_SYNC what it mostly could provide is to make sure the dirty data goes and sit on disk. But I guess it won't provide guarantee that in case if the data is journalled then it is moved to it's right location on disk before the results are returned to user.
So I understood the coherency part. But why do you say atomicity? How does bmap() interface provides atomicity() ?

Sure thanks for this. Somehow I feel that the callback will be a similar API to what a_ops->bmap() does today.

So from jbd2 perspective will the new block mapping callback needs same level of coherency and atomicity guarantee?

Thanks
-ritesh

And we also need to eventually phase generic_swapfile_activate out, maybe by having a version with a get_blocks callback for the non-iomap case.

I think this wants to use iomap, as that would solve all the problems.

This probably needs to use the in-kernel direct I/O interface, just as it is planned for cachefiles.

Well, there are two problems with this - firstly, ocfs2 is also using jbd2 and it knows nothing about iomap. So that would have to be implemented. Secondly, you have to somehow pass iomap ops to jbd2 so it all boils down to passing some callback to jbd2 during journal init to map blocks anyway as Dave said. And then it is upto filesystem to do the mapping - usually directly using its internal block mapping function - so no need for iomap AFAICT.
Honza

Jan Kara <[email protected]>
SUSE Labs, CR

You'll need to describe the mapping some how. So why not reuse an existing mechanism instead of creating a new ad-hoc one?

Well, we could argue that bmap() is an "existing mechanism" --- again, bmap() returns a u64, so it's perfectly fine. It's FIBMAP which is "fundamentally broken", not bmap(). If the goal is to eventually eliminate bmap() and aops->bmap(), sure, then we should force march all file systems to use iomap_bmap(), including ocfs2.

Otherwise, if the goal alert users of FIBMAP when it's returning an corrutped block number, why not move the check if the block is larger than INT_MAX to ioctl_fibmap() in fs/ioctl.c, instead of in iomap_bmap()?

If we can't fix this, I'm beginning to think that switching to iomap for fiemap and bmap is actually a lose for ext4. It's causing performance regressions, and now we see it's causing functionality regressions. Sure, it's saving a bit of code size, but is it really worth it to use iomap for fiemap/bmap?

- Ted

https://bugzilla.kernel.org/show_bug.cgi?id=207367

Darrick J. Wong ([email protected]) changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #4 from Darrick J. Wong ([email protected]) --- Yikes, jbd2 really ought to be ported to a newer internal API than bmap...

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #5 from [email protected] ---
Hello All,

Sorry about not seeing this through in the first place.

So the problem really is that the iomap_bmap() API gives WARNING and does't return the physical block address in case if the addr is > INT_MAX. (I guess this could be mostly since the ioctl_fibmap() passes a user integer pointer and users of iomap_bmap() may mostly be coming from ioctl path till now).

FYI - I do see that bmap() is also used by below APIs/subsystem. Not sure if any of subsystems mentioned below may still fail later if the underlying FS moved to iomap_bmap() interface or for any existing callers of iomap_bmap() :-

1. mm/page-io.c (generic_swapfile_activate() func)
2. fs/cachefiles/rdwr.c
3. fs/ecryptfs/mmap.c
4. fs/jbd2/journal.c

But the changes done in ext4 to move to iomap_bmap() interface resulted in this issue since jbd2 tries to find the block mapping of on disk journal inode of ext4 and on a larger filesystem this may fail given the design of iomap_bmap() to not return addr if > INT_MAX.

So as I see it there are 3 options from here. Wanted to put this on mailing list for discussion.

1. Make changes in iomap_bmap() to return the block address mapping. But I still would like to mention that iomap designers may not agree with this here Since the direction in general is to get rid of bmap() interface anyways.

2. Revert the patch series of "bmap & fiemap to move to iomap interface" (why fiemap too? - since if we decide to revert bmap anyways, then we better fix the performance numbers report too coming from fiemap. Also due to 3rd option below since if iomap_bmap() is not changed, then we better keep both of this interface as is until we get the solution like 3 below.)

3. To move to a new internal API like fiemap. But we need to change fiemap in a way that it should also be allowed to used by internal kernel APIs. Since as of now fiemap_extent struct is assumed to be a user pointer.

(But the 3rd option as I see, won't be possible given the time frame to fix this issue. Also note if we decide to revert the changes, then the long term path would be to work on making fiemap used by internal kernel APIs too).

struct fiemap_extent_info {
unsigned int fi_flags; /* Flags as passed from user */
unsigned int fi_extents_mapped; /* Number of mapped extents */
unsigned int fi_extents_max; /* Size of fiemap_extent array */
struct fiemap_extent __user *fi_extents_start; /* Start of
fiemap_extent array */
};

-ritesh

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #6 from Dave Chinner ([email protected]) ---

No, it's because bmap is fundamentally broken when it comes to block ranges > INT_MAX. The filesystem in question is a >16TB filesystem, so the block range for that filesystem is >32bits, and hence usage of bmap in the jbd2 code is broken.

Basically, jbd2 needs fixing to be able to map blocks that are at higher offsets than bmap can actually report.

Filesystems using iomap infrastructure should be providing aops->swap_activate() to map swapfile extents via iomap_swapfile_activate() (e.g. see xfs_iomap_swapfile_activate()), not using generic_swapfile_activate().

Known problem, work being done to stop using bmap() here

Just a wrapper to pass ->bmap calls through to the lower layer.

Broken on filesystems where the journal file might be placed beyond a 32 bit block number, iomap_bmap() just makes that obvious. Needs fixing.

You also missed f2fs copy-n-waste using it for internal swapfile mapping:

/* Copied from generic_swapfile_activate() to check any holes */

That needs fixing, too.

And you missed the MD bitmap code uses bmap() to map it's bitmap storage file, which means that is broken is the bitmap file is on a filesystem/block device > 16TB, too...

Nope. bmap() is broken. Get rid of it.

The use of bmap was broken prior to this conversion - shooting the messenger doesn't fix the problem. Get rid of bmap().

Fiemap cannot be used this way. It's a diagnostic interface that provides no guarantee of coherency or atomicity, so you can't use it in this way in userspace or the kernel.

IMO, the correct thing to do is for the caller to supply jbd with a block mapping callback. i.e. jbd2_journal_init_inode() gets called from both ext4 and ocfs2 with a callback that does the block mapping for that specific filesystem. Indeed, jbd2 will need to cache that callback, because it needs to call it to map journal blocks when committing transactions....

Cheers,

Dave.

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #7 from [email protected] ---
Hello,

IIUC, what you meant is that bmap in general as a interface is broken because if some user tries to call this interface via an ioctl for a file which is placed beyond 32 bits on a filesystem, then it truncates the results (basically gives us wrong results). Also this means as a user interface this was not designed properly keeping the block addresses range in mind (that someday it will extent beyong 32 bits).

Due to above reason, we don't make iomap_bmap() API return the u64 addr in it's argument, even though it is capable of doing that. Is that the reason?
And this is because since the overall interface from userspace side is broken and so we want to get rid of that.

So what I would still like to understand is- that bmap() internal kernel function can definitely handle the sector_t block addresses, right? Isn't the bmap() kernel function was designed for this purpose in mind, to help internal kernel callers to provide with u64 block addresses?

But for e.g. here, when jbd2 calls for bmap(), it will eventually call for ext4_bmap() -> iomap_bmap(). Now even though this chain is capable of handling u64 addresses, but it's the iomap_bmap() which doesn't provide this. So the question simply is why?

Sorry about my query here, it is to only to understand more about this and to not force in anyway to change iomap_bmap() to just get this working.

Sure.

hmm. Yes, I guess even with FIEMAP_FLAG_SYNC what it mostly could provide is to make sure the dirty data goes and sit on disk. But I guess it won't provide guarantee that in case if the data is journalled then it is moved to it's right location on disk before the results are returned to user.
So I understood the coherency part. But why do you say atomicity? How does bmap() interface provides atomicity() ?

Sure thanks for this. Somehow I feel that the callback will be a similar API to what a_ops->bmap() does today.

So from jbd2 perspective will the new block mapping callback needs same level of coherency and atomicity guarantee?

Thanks
-ritesh

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #8 from [email protected] ---

And we also need to eventually phase generic_swapfile_activate out, maybe by having a version with a get_blocks callback for the non-iomap case.

I think this wants to use iomap, as that would solve all the problems.

This probably needs to use the in-kernel direct I/O interface, just as it is planned for cachefiles.

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #9 from walter59 ([email protected]) --- hey at all,

me use it at two servers, run without on 5.6

not at 5.7_rcx

over 16 TB vol. --- btrfs runs on same device -- so it only can be in ext4 subsys

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #10 from Jan Kara ([email protected]) ---

Well, there are two problems with this - firstly, ocfs2 is also using jbd2 and it knows nothing about iomap. So that would have to be implemented. Secondly, you have to somehow pass iomap ops to jbd2 so it all boils down to passing some callback to jbd2 during journal init to map blocks anyway as Dave said. And then it is upto filesystem to do the mapping - usually directly using its internal block mapping function - so no need for iomap AFAICT.
Honza

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #11 from [email protected] ---

You'll need to describe the mapping some how. So why not reuse an existing mechanism instead of creating a new ad-hoc one?

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #12 from walter59 ([email protected]) --- all about this why it is running on kernel 5.6 and before

You are receiving this mail because:
You are watching the assignee of the bug.

https://bugzilla.kernel.org/show_bug.cgi?id=207367

--- Comment #13 from Theodore Tso ([email protected]) ---

Well, we could argue that bmap() is an "existing mechanism" --- again, bmap() returns a u64, so it's perfectly fine. It's FIBMAP which is "fundamentally broken", not bmap(). If the goal is to eventually eliminate bmap() and aops->bmap(), sure, then we should force march all file systems to use iomap_bmap(), including ocfs2.

Otherwise, if the goal alert users of FIBMAP when it's returning an corrutped block number, why not move the check if the block is larger than INT_MAX to ioctl_fibmap() in fs/ioctl.c, instead of in iomap_bmap()?

If we can't fix this, I'm beginning to think that switching to iomap for fiemap and bmap is actually a lose for ext4. It's causing performance regressions, and now we see it's causing functionality regressions. Sure, it's saving a bit of code size, but is it really worth it to use iomap for fiemap/bmap?

- Ted

You are receiving this mail because:
You are watching the assignee of the bug.