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authorDavid Howells <dhowells@redhat.com>2022-01-24 21:13:24 +0000
committerSteve French <stfrench@microsoft.com>2023-02-20 18:36:02 -0600
commitd08089f649a0cfb2099c8551ac47eef0cc23fdf2 (patch)
tree1165d72f35311d1017bf84c417cee6c37b3c01d9 /fs/cifs/fscache.h
parent16541195c6d9bcad568b7c6afbf855ddc3a856aa (diff)
cifs: Change the I/O paths to use an iterator rather than a page list
Currently, the cifs I/O paths hand lists of pages from the VM interface routines at the top all the way through the intervening layers to the socket interface at the bottom. This is a problem, however, for interfacing with netfslib which passes an iterator through to the ->issue_read() method (and will pass an iterator through to the ->issue_write() method in future). Netfslib takes over bounce buffering for direct I/O, async I/O and encrypted content, so cifs doesn't need to do that. Netfslib also converts IOVEC-type iterators into BVEC-type iterators if necessary. Further, cifs needs foliating - and folios may come in a variety of sizes, so a page list pointing to an array of heterogeneous pages may cause problems in places such as where crypto is done. Change the cifs I/O paths to hand iov_iter iterators all the way through instead. Notes: (1) Some old routines are #if'd out to be removed in a follow up patch so as to avoid confusing diff, thereby making the diff output easier to follow. I've removed functions that don't overlap with anything added. (2) struct smb_rqst loses rq_pages, rq_offset, rq_npages, rq_pagesz and rq_tailsz which describe the pages forming the buffer; instead there's an rq_iter describing the source buffer and an rq_buffer which is used to hold the buffer for encryption. (3) struct cifs_readdata and cifs_writedata are similarly modified to smb_rqst. The ->read_into_pages() and ->copy_into_pages() are then replaced with passing the iterator directly to the socket. The iterators are stored in these structs so that they are persistent and don't get deallocated when the function returns (unlike if they were stack variables). (4) Buffered writeback is overhauled, borrowing the code from the afs filesystem to gather up contiguous runs of folios. The XARRAY-type iterator is then used to refer directly to the pagecache and can be passed to the socket to transmit data directly from there. This includes: cifs_extend_writeback() cifs_write_back_from_locked_folio() cifs_writepages_region() cifs_writepages() (5) Pages are converted to folios. (6) Direct I/O uses netfs_extract_user_iter() to create a BVEC-type iterator from an IOBUF/UBUF-type source iterator. (7) smb2_get_aead_req() uses netfs_extract_iter_to_sg() to extract page fragments from the iterator into the scatterlists that the crypto layer prefers. (8) smb2_init_transform_rq() attached pages to smb_rqst::rq_buffer, an xarray, to use as a bounce buffer for encryption. An XARRAY-type iterator can then be used to pass the bounce buffer to lower layers. Signed-off-by: David Howells <dhowells@redhat.com> cc: Steve French <sfrench@samba.org> cc: Shyam Prasad N <nspmangalore@gmail.com> cc: Rohith Surabattula <rohiths.msft@gmail.com> cc: Paulo Alcantara <pc@cjr.nz> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cifs@vger.kernel.org Link: https://lore.kernel.org/r/164311907995.2806745.400147335497304099.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/164928620163.457102.11602306234438271112.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165211420279.3154751.15923591172438186144.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165348880385.2106726.3220789453472800240.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/165364827111.3334034.934805882842932881.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/166126396180.708021.271013668175370826.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/166697259595.61150.5982032408321852414.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166732031756.3186319.12528413619888902872.stgit@warthog.procyon.org.uk/ # rfc Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs/fscache.h')
-rw-r--r--fs/cifs/fscache.h10
1 files changed, 5 insertions, 5 deletions
diff --git a/fs/cifs/fscache.h b/fs/cifs/fscache.h
index 67b601041f0a..173999610997 100644
--- a/fs/cifs/fscache.h
+++ b/fs/cifs/fscache.h
@@ -90,7 +90,7 @@ static inline int cifs_fscache_query_occupancy(struct inode *inode,
}
extern int __cifs_readpage_from_fscache(struct inode *pinode, struct page *ppage);
-extern void __cifs_readpage_to_fscache(struct inode *pinode, struct page *ppage);
+extern void __cifs_readahead_to_fscache(struct inode *pinode, loff_t pos, size_t len);
static inline int cifs_readpage_from_fscache(struct inode *inode,
@@ -101,11 +101,11 @@ static inline int cifs_readpage_from_fscache(struct inode *inode,
return -ENOBUFS;
}
-static inline void cifs_readpage_to_fscache(struct inode *inode,
- struct page *page)
+static inline void cifs_readahead_to_fscache(struct inode *inode,
+ loff_t pos, size_t len)
{
if (cifs_inode_cookie(inode))
- __cifs_readpage_to_fscache(inode, page);
+ __cifs_readahead_to_fscache(inode, pos, len);
}
#else /* CONFIG_CIFS_FSCACHE */
@@ -141,7 +141,7 @@ cifs_readpage_from_fscache(struct inode *inode, struct page *page)
}
static inline
-void cifs_readpage_to_fscache(struct inode *inode, struct page *page) {}
+void cifs_readahead_to_fscache(struct inode *inode, loff_t pos, size_t len) {}
#endif /* CONFIG_CIFS_FSCACHE */