Re: [BUG?] invalidate_lock not held in read_cache_folio()

[Dev Jain <dev.jain@arm.com>]

On 08/06/26 5:49 pm, Matthew Wilcox wrote:
> On Mon, Jun 08, 2026 at 04:54:51PM +0530, Dev Jain wrote:
>> Hi,
>>
>> My understanding is that there are two ways we are serializing against concurrent
>> addition of a folio into the pagecache (see 730633f0b7f9).
>>
>> The kerneldoc of read_cache_folio() says:
>>
>> "Context: May sleep.  Expects mapping->invalidate_lock to be held."
>>
>> I put the following in __filemap_add_folio():
>>
>> +       BUG_ON(!inode_is_locked(mapping->host) &&
>> +              !rwsem_is_locked(&mapping->invalidate_lock));
>>
>>
>> And got the following trace:
>>
>>
>> [    0.115587] Call trace:
>> [    0.115686]  __filemap_add_folio+0x5dc/0x680 (P)
>> [    0.115871]  filemap_add_folio+0xec/0x2d0
>> [    0.116031]  do_read_cache_folio+0x144/0x2d8
>> [    0.116194]  read_cache_folio+0x1c/0x30
>> [    0.116344]  read_part_sector+0x4c/0xf0
>> [    0.116499]  read_lba+0xb0/0x1a0
>> [    0.116627]  efi_partition+0xa8/0x740
>> [    0.116769]  bdev_disk_changed+0x238/0x620
>> [    0.116939]  blkdev_get_whole+0xac/0x100
>> [    0.117090]  bdev_open+0x280/0x3c0
> 
> You can't truncate or holepunch a bdev

Yep, I realized that later, thanks : )

Just that the kerneldoc says "Expects mapping->invalidate_lock to be held"
so was wondering whether this comment is appropriate. Difficult for me to
reason about that since this goes into fs/block code.