On 8/18/24 22:16, David Howells wrote:
Pankaj Raghav (Samsung) <kernel@xxxxxxxxxxxxxxxx> wrote:
I am no expert in network filesystems but are you sure there are no
PAGE_SIZE assumption when manipulating folios from the page cache in
AFS?
Note that I've removed the knowledge of the pagecache from 9p, afs and cifs to
netfslib and intend to do the same to ceph. The client filesystems just
provide read and write ops to netfslib and netfslib uses those to do ordinary
buffered I/O, unbuffered I/O (selectable by mount option on some filesystems)
and DIO.
That said, I'm not sure that I haven't made some PAGE_SIZE assumptions. I
don't *think* I have since netfslib is fully multipage folio capable, but I
can't guarantee it.
I guess you did:
static int afs_fill_super(struct super_block *sb, struct afs_fs_context
*ctx)
{
struct afs_super_info *as = AFS_FS_S(sb);
struct inode *inode = NULL;
int ret;
_enter("");
/* fill in the superblock */
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_magic = AFS_FS_MAGIC;
sb->s_op = &afs_super_ops;
IE you essentially nail AFS to use PAGE_SIZE.
Not sure how you would tell AFS to use a different block size;
maybe a mount option?
And there are several other places which will need to be modified;
eg afs_mntpt_set_params() is trying to read from a page which
won't fly with large blocks (converted to read_full_folio()?),
and, of course, the infamous AFS_DIR_BLOCKS_PER_PAGE which will
overflow for large blocks.
So some work is required, but everything looks doable.
Maybe I can find some time until LPC.
Mostly this was just a note to you that there might be an issue with your code
- but I haven't investigated it yet and it could well be in my code.
Hmm. I'd rather fix the obvious places in afs first; just do a quick
grep for 'PAGE_', that'll give you a good impression of places to look at.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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