Hi Alex,
Aneesh Kumar K.V wrote:
I checked the logs today for the fsstress run i found this in my dmesg
log. The
same stack trace is repeated for many times
uh! busy PA
Call Trace:
[c0000000efa72fc0] [c00000000000fe30] .show_stack+0x6c/0x1a0 (unreliable)
[c0000000efa73060] [c0000000001954a0]
.ext4_mb_discard_group_preallocations+0x208/0x4fc
[c0000000efa73180] [c0000000001957c8]
.ext4_mb_discard_preallocations+0x34/0x94
[c0000000efa73220] [c000000000197fc8] .ext4_mb_new_blocks+0x1fc/0x2c0
[c0000000efa733a0] [c00000000018dfb4] .ext4_ext_get_blocks+0x540/0x6f8
[c0000000efa734d0] [c00000000017bfe8] .ext4_get_block+0x12c/0x1b4
[c0000000efa73580] [c000000000109104] .__blockdev_direct_IO+0x554/0xb94
[c0000000efa736b0] [c000000000179b28] .ext4_direct_IO+0x138/0x208
[c0000000efa73790] [c00000000009a314] .generic_file_direct_IO+0x134/0x1a0
[c0000000efa73840] [c00000000009a404] .generic_file_direct_write+0x84/0x150
[c0000000efa73900] [c00000000009bf54]
.__generic_file_aio_write_nolock+0x2c4/0x3d4
[c0000000efa73a00] [c00000000009c0e4] .generic_file_aio_write+0x80/0x114
[c0000000efa73ac0] [c000000000175c90] .ext4_file_write+0x2c/0xd4
[c0000000efa73b50] [c0000000000d0cf4] .do_sync_write+0xc4/0x124
[c0000000efa73cf0] [c0000000000d16bc] .vfs_write+0x120/0x1f4
[c0000000efa73d90] [c0000000000d21a8] .sys_write+0x4c/0x8c
[c0000000efa73e30] [c00000000000852c] syscall_exit+0x0/0x40
uh! busy PA
I think we can remove from the code this dump_stack.
list_for_each_entry_safe(pa, tmp,
&grp->bb_prealloc_list, pa_group_list) {
spin_lock(&pa->pa_lock);
if (atomic_read(&pa->pa_count)) {
spin_unlock(&pa->pa_lock);
printk(KERN_ERR "uh! busy PA\n");
dump_stack();
busy = 1;
continue;
}
This happens during ext4_mb_discard_group_prealloction. It is quiet possible that
during the discard operation some other CPUs can use the preallocated space right ?
Infact down the code we see if we have skipped some of the PA (busy == 1 )and the
free space retrieved is not enough they we loop again
Can you let me know why we marked the dump_stack there ?
-aneesh
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