On 11/06/2024 10:41, Pankaj Raghav (Samsung) wrote:
8419fcc7..9f791db473e4 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1990,6 +1990,12 @@ EXPORT_SYMBOL_GPL(iomap_writepages);
static int __init iomap_init(void)
{
+ int ret;
+
+ ret = iomap_dio_init();
+ if (ret)
+ return ret;
+
return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
offsetof(struct iomap_ioend, io_bio),
BIOSET_NEED_BVECS);
I suppose that it does not matter that zero_fs_block is leaked if this fails
(or is it even leaked?), as I don't think that failing that bioset_init()
call is handled at all.
If bioset_init fails, then we have even more problems than just a leaked
64k memory? 😉
Right
> Do you have something like this in mind?
I wouldn't propose anything myself. AFAICS, we don't gracefully handle
bioset_init() failing and iomap_ioend_bioset not being initialized properly.
static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter,
struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf)
{
+
static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter,
struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf)
{
@@ -236,17 +253,22 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
loff_t pos, unsigned len)
{
struct inode *inode = file_inode(dio->iocb->ki_filp);
- struct page *page = ZERO_PAGE(0);
struct bio *bio;
+ /*
+ * Max block size supported is 64k
+ */
+ WARN_ON_ONCE(len > ZERO_FSB_SIZE);
JFYI, As mentioned inhttps://urldefense.com/v3/__https://lore.kernel.org/linux-xfs/20240429174746.2132161-1-john.g.garry@xxxxxxxxxx/T/*m5354e2b2531a5552a8b8acd4a95342ed4d7500f2__;Iw!!ACWV5N9M2RV99hQ!MTwVaC6oueHR_vgmDfOvgBX8bPdeTSRPcRcw5-CqtHnFEH-Ya1sUeZwaF-xrBF5XZ_8lJw5l-riq4t8IkfBhf2Q$ ,
we would like to support an arbitrary size. Maybe I will need to loop for
zeroing sizes > 64K.
The initial patches were looping with a ZERO_PAGE(0), but the initial
feedback was to use a huge zero page. But when I discussed that at LSF,
the people thought we will be using a lot of memory for sub-block
memory, especially on architectures with 64k base page size.
So for now a good tradeoff between memory usage and efficiency was to
use a 64k buffer as that is the maximum FSB we support.[1]
IIUC, you will be using this function also to zero out the extent and
not just a FSB?
Right. Or more specifically, the FS can ask for the zeroing size.
Typically it will be inode i_blocksize, but the FS can ask for a larger
size to zero out to extent alignment boundaries.
I think we could resort to looping until we have a way to request
arbitrary zero folios without having to allocate at it in
iomap_dio_alloc_bio() for every IO.
ok
[1]https://urldefense.com/v3/__https://lore.kernel.org/linux-xfs/20240529134509.120826-8-kernel@xxxxxxxxxxxxxxxx/__;!!ACWV5N9M2RV99hQ!MTwVaC6oueHR_vgmDfOvgBX8bPdeTSRPcRcw5-CqtHnFEH-Ya1sUeZwaF-xrBF5XZ_8lJw5l-riq4t8Ij2hl9yU$
Thanks,
John
