On Sat, Feb 01, 2020 at 07:12:28AM -0800, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <[email protected]>
>
> I would particularly value feedback on this from the gfs2 and ocfs2
> maintainers. They have non-trivial changes, and a review on patch 5
> would be greatly appreciated.
>
> This series adds a readahead address_space operation to eventually
> replace the readpages operation. The key difference is that
> pages are added to the page cache as they are allocated (and
> then looked up by the filesystem) instead of passing them on a
> list to the readpages operation and having the filesystem add
> them to the page cache. It's a net reduction in code for each
> implementation, more efficient than walking a list, and solves
> the direct-write vs buffered-read problem reported by yu kuai at
> https://lore.kernel.org/linux-fsdevel/[email protected]/
>
> v4:
> - Rebase on current Linus (a62aa6f7f50a ("Merge tag 'gfs2-for-5.6'"))
I've tried to test the patchset but haven't got very far, it crashes at boot
ritht after VFS mounts the root. The patches are from mailinglist, applied on
current master, bug I saw the same crash with the git branch in your
repo (probably v1).
(gdb) l *(ext4_mpage_readpages+0x1da/0xc20)
0xffffffff813753f0 is in ext4_mpage_readpages (fs/ext4/readpage.c:226).
221 return i_size_read(inode);
222 }
223
224 int ext4_mpage_readpages(struct address_space *mapping, pgoff_t start,
225 struct page *page, unsigned nr_pages, bool is_readahead)
226 {
227 struct bio *bio = NULL;
228 sector_t last_block_in_bio = 0;
229
230 struct inode *inode = mapping->host;
[ 8.008531] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 8.011482] #PF: supervisor read access in kernel mode
[ 8.014121] #PF: error_code(0x0000) - not-present page
[ 8.016767] PGD 0 P4D 0
[ 8.018352] Oops: 0000 [#1] SMP
[ 8.019716] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.5.0-default+ #955
[ 8.021746] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
[ 8.025244] RIP: 0010:ext4_mpage_readpages+0x1da/0xc20
[ 8.026817] Code: 7c 24 4e 00 0f 85 23 04 00 00 44 29 74 24 3c 83 6c 24 48 01 0f 84 4d 04 00 00 80 7c 24 4e 00 0f 85 fc 05 00 00 48 8b 4c 24 18 <48> 8b 01 f6 c4 20 75 89 4c 8b 69 20 b9 0c 00 00 00 2b 4c 24 38 83
[ 8.031957] RSP: 0000:ffffb34f40013988 EFLAGS: 00010292
[ 8.033691] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 8.035533] RDX: 0000000000000001 RSI: ffffffff960934c0 RDI: ffffffff9681a080
[ 8.036900] RBP: 0000000000000001 R08: ffffb34f40013a68 R09: 0000000000000000
[ 8.038461] R10: 0000000000000038 R11: 0000000000000000 R12: 0000000000000004
[ 8.040698] R13: ffff9668ba4e18e0 R14: 0000000000000001 R15: 0000000000000000
[ 8.042805] FS: 0000000000000000(0000) GS:ffff9668bda00000(0000) knlGS:0000000000000000
[ 8.045396] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 8.047233] CR2: 0000000000000000 CR3: 000000002e011001 CR4: 0000000000160ee0
[ 8.049337] Call Trace:
[ 8.050435] ? __lock_acquire+0xee0/0x1320
[ 8.051833] ? release_pages+0x310/0x380
[ 8.053265] ? mark_held_locks+0x50/0x80
[ 8.054468] ext4_readahead+0x3b/0x50
[ 8.055877] read_pages+0x65/0x1a0
[ 8.057167] ? put_pages_list+0x90/0x90
[ 8.058689] __do_page_cache_readahead+0x24b/0x2a0
[ 8.060394] generic_file_buffered_read+0x7cf/0x9f0
[ 8.062137] ? sched_clock+0x5/0x10
[ 8.063451] ? up_read+0x18/0x240
[ 8.064774] ? ext4_xattr_get+0x97/0x2c0
[ 8.066178] new_sync_read+0x111/0x1a0
[ 8.067423] vfs_read+0xc5/0x180
[ 8.068572] kernel_read+0x2c/0x40
[ 8.069788] prepare_binprm+0x171/0x1b0
[ 8.071311] load_script+0x1c1/0x250
[ 8.072643] search_binary_handler+0x5f/0x210
[ 8.074135] exec_binprm+0xd7/0x290
[ 8.075463] __do_execve_file.isra.0+0x570/0x800
[ 8.077400] ? rest_init+0x2f1/0x2f5
[ 8.078979] do_execve+0x21/0x30
[ 8.080420] kernel_init+0xa4/0x11b
[ 8.081856] ? rest_init+0x2f5/0x2f5
[ 8.083173] ret_from_fork+0x24/0x30
[ 8.084695] Modules linked in:
[ 8.086055] CR2: 0000000000000000
[ 8.087572] ---[ end trace 0890c371a706b34a ]---
[ 8.089417] RIP: 0010:ext4_mpage_readpages+0x1da/0xc20
[ 8.116836] BUG: sleeping function called from invalid context at include/linux/percpu-rwsem.h:38
[ 8.119626] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0
[ 8.122392] INFO: lockdep is turned off.
[ 8.123694] irq event stamp: 18341344
[ 8.124735] hardirqs last enabled at (18341343): [<ffffffff95230c42>] free_unref_page_list+0x232/0x270
[ 8.127918] hardirqs last disabled at (18341344): [<ffffffff95002b4b>] trace_hardirqs_off_thunk+0x1a/0x1c
[ 8.131145] softirqs last enabled at (18341250): [<ffffffff95a00358>] __do_softirq+0x358/0x52b
[ 8.143060] softirqs last disabled at (18341243): [<ffffffff9508ae3d>] irq_exit+0x9d/0xb0
[ 8.145603] CPU: 2 PID: 1 Comm: swapper/0 Tainted: G D 5.5.0-default+ #955
[ 8.148474] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
[ 8.152440] Call Trace:
[ 8.153747] dump_stack+0x71/0xa0
[ 8.155238] ___might_sleep.cold+0xa6/0xf9
[ 8.156903] exit_signals+0x31/0x310
[ 8.158431] ? __do_execve_file.isra.0+0x570/0x800
[ 8.160179] do_exit+0xa8/0xd60
[ 8.161632] ? rest_init+0x2f1/0x2f5
[ 8.163204] rewind_stack_do_exit+0x17/0x20
[ 8.164931] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
[ 8.167575] Kernel Offset: 0x14000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
On Tue, Feb 04, 2020 at 04:32:27PM +0100, David Sterba wrote:
> On Sat, Feb 01, 2020 at 07:12:28AM -0800, Matthew Wilcox wrote:
> > From: "Matthew Wilcox (Oracle)" <[email protected]>
> >
> > I would particularly value feedback on this from the gfs2 and ocfs2
> > maintainers. They have non-trivial changes, and a review on patch 5
> > would be greatly appreciated.
> >
> > This series adds a readahead address_space operation to eventually
> > replace the readpages operation. The key difference is that
> > pages are added to the page cache as they are allocated (and
> > then looked up by the filesystem) instead of passing them on a
> > list to the readpages operation and having the filesystem add
> > them to the page cache. It's a net reduction in code for each
> > implementation, more efficient than walking a list, and solves
> > the direct-write vs buffered-read problem reported by yu kuai at
> > https://lore.kernel.org/linux-fsdevel/[email protected]/
> >
> > v4:
> > - Rebase on current Linus (a62aa6f7f50a ("Merge tag 'gfs2-for-5.6'"))
>
> I've tried to test the patchset but haven't got very far, it crashes at boot
> ritht after VFS mounts the root. The patches are from mailinglist, applied on
> current master, bug I saw the same crash with the git branch in your
> repo (probably v1).
Yeah, I wasn't able to test at the time due to what turned out to be
the hpet bug in Linus' tree. Now that's fixed, I've found & fixed a
couple more bugs. There'll be a v5 once I fix the remaining problem
(looks like a missing page unlock somewhere).