Hi,
在 2023/12/06 22:58, Matthew Wilcox 写道:
On Tue, Dec 05, 2023 at 08:37:15PM +0800, Yu Kuai wrote:
+struct folio *bdev_read_folio(struct block_device *bdev, pgoff_t index)
+{
+ return read_mapping_folio(bdev->bd_inode->i_mapping, index, NULL);
+}
+EXPORT_SYMBOL_GPL(bdev_read_folio);
I'm coming to the opinion that 'index' is the wrong parameter here.
Looking through all the callers of bdev_read_folio() in this patchset,
they all have a position in bytes, and they all convert it to
index for this call. The API should probably be:
struct folio *bdev_read_folio(struct block_device *bdev, loff_t pos)
{
return read_mapping_folio(bdev->bd_inode->i_mapping,
pos / PAGE_SIZE, NULL);
}
Thanks for reviewing this patchset! Okay, I'll convert to pass in "pos"
in v2.
... and at some point, we'll get round to converting read_mapping_folio()
to take its argument in loff_t.
Similiarly for these two APIs:
+struct folio *bdev_read_folio_gfp(struct block_device *bdev, pgoff_t index,
+ gfp_t gfp)
+struct folio *bdev_get_folio(struct block_device *bdev, pgoff_t index)
+struct folio *bdev_find_or_create_folio(struct block_device *bdev,
+ pgoff_t index, gfp_t gfp)
+{
+ return __filemap_get_folio(bdev->bd_inode->i_mapping, index,
+ FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
+}
+EXPORT_SYMBOL_GPL(bdev_find_or_create_folio);
This one probably shouldn't exist. I've been converting callers of
find_or_create_page() to call __filemap_get_folio; I suspect we
should expose a __bdev_get_folio and have the callers use the FGP
arguments directly, but I'm open to other opinions here.
If nobody against this, I will expose single __bdev_get_folio() to use
in v2.
+void bdev_sync_readahead(struct block_device *bdev, struct file_ra_state *ra,
+ struct file *file, pgoff_t index,
+ unsigned long req_count)
+{
+ struct file_ra_state tmp_ra = {};
+
+ if (!ra) {
+ ra = &tmp_ra;
+ file_ra_state_init(ra, bdev->bd_inode->i_mapping);
+ }
+ page_cache_sync_readahead(bdev->bd_inode->i_mapping, ra, file, index,
+ req_count);
+}
I think the caller should always be passing in a valid file_ra_state.
It's only cramfs that doesn't have one, and it really should!
Not entirely sure about the arguments here; part of me says "bytes",
but this is weird enough to maybe take arguments in pages.
In fact, bdev_sync_readahead() is only called for cramfs and ext4.
For ext4 it's used in ext4_readdir() so there is valid file_ra_state.
Hoever, for cramfs it's used in cramfs_read(), and cramfs_read() is used
for:
1) cramfs_read_folio
2) cramfs_readdir
3) cramfs_lookup
4) cramfs_read_super
Looks like it's easy to pass in valid file_ra_state() for 1) and 2),
however, I don't see an easy way to do this for 3) and 4).
Thanks,
Kuai
.
