Re: [PATCH -next RFC 01/14] block: add some bdev apis

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]



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);

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,

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

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).



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux ARM Kernel]     [Linux Filesystem Development]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux