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authorDavid Howells <dhowells@redhat.com>2022-11-01 14:52:47 +0000
committerSteve French <stfrench@microsoft.com>2023-02-20 17:25:43 -0600
commit4e260a8fd740aa0dcecafe79c4f9d3013a21f1ca (patch)
treee9f87533b77133aa0c1476a8abfa3fd804820f95
parent7c8e01ebf2361eb397f32cd1c8ee402dda48dce0 (diff)
cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE
Provide cifs_splice_read() to use a bvec rather than an pipe iterator as the latter cannot so easily be split and advanced, which is necessary to pass an iterator down to the bottom levels. Upstream cifs gets around this problem by using iov_iter_get_pages() to prefill the pipe and then passing the list of pages down. This is done by: (1) Bulk-allocate a bunch of pages to carry as much of the requested amount of data as possible, but without overrunning the available slots in the pipe and add them to an ITER_BVEC. (2) Synchronously call ->read_iter() to read into the buffer. (3) Discard any unused pages. (4) Load the remaining pages into the pipe in order and advance the head pointer. 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: Jeff Layton <jlayton@kernel.org> cc: Al Viro <viro@zeniv.linux.org.uk> cc: linux-cifs@vger.kernel.org Link: https://lore.kernel.org/r/166732028113.3186319.1793644937097301358.stgit@warthog.procyon.org.uk/ # rfc Signed-off-by: Steve French <stfrench@microsoft.com>
-rw-r--r--fs/cifs/cifsfs.c12
-rw-r--r--fs/cifs/cifsfs.h3
-rw-r--r--fs/cifs/file.c16
3 files changed, 25 insertions, 6 deletions
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 10e00c624922..4f1afcd3f8be 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1358,7 +1358,7 @@ const struct file_operations cifs_file_ops = {
.fsync = cifs_fsync,
.flush = cifs_flush,
.mmap = cifs_file_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = cifs_splice_read,
.splice_write = iter_file_splice_write,
.llseek = cifs_llseek,
.unlocked_ioctl = cifs_ioctl,
@@ -1378,7 +1378,7 @@ const struct file_operations cifs_file_strict_ops = {
.fsync = cifs_strict_fsync,
.flush = cifs_flush,
.mmap = cifs_file_strict_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = cifs_splice_read,
.splice_write = iter_file_splice_write,
.llseek = cifs_llseek,
.unlocked_ioctl = cifs_ioctl,
@@ -1398,7 +1398,7 @@ const struct file_operations cifs_file_direct_ops = {
.fsync = cifs_fsync,
.flush = cifs_flush,
.mmap = cifs_file_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = direct_splice_read,
.splice_write = iter_file_splice_write,
.unlocked_ioctl = cifs_ioctl,
.copy_file_range = cifs_copy_file_range,
@@ -1416,7 +1416,7 @@ const struct file_operations cifs_file_nobrl_ops = {
.fsync = cifs_fsync,
.flush = cifs_flush,
.mmap = cifs_file_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = cifs_splice_read,
.splice_write = iter_file_splice_write,
.llseek = cifs_llseek,
.unlocked_ioctl = cifs_ioctl,
@@ -1434,7 +1434,7 @@ const struct file_operations cifs_file_strict_nobrl_ops = {
.fsync = cifs_strict_fsync,
.flush = cifs_flush,
.mmap = cifs_file_strict_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = cifs_splice_read,
.splice_write = iter_file_splice_write,
.llseek = cifs_llseek,
.unlocked_ioctl = cifs_ioctl,
@@ -1452,7 +1452,7 @@ const struct file_operations cifs_file_direct_nobrl_ops = {
.fsync = cifs_fsync,
.flush = cifs_flush,
.mmap = cifs_file_mmap,
- .splice_read = generic_file_splice_read,
+ .splice_read = direct_splice_read,
.splice_write = iter_file_splice_write,
.unlocked_ioctl = cifs_ioctl,
.copy_file_range = cifs_copy_file_range,
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 63a0ac2b9355..25decebbc478 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -100,6 +100,9 @@ extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to);
extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from);
extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from);
extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from);
+extern ssize_t cifs_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags);
extern int cifs_flock(struct file *pfile, int cmd, struct file_lock *plock);
extern int cifs_lock(struct file *, int, struct file_lock *);
extern int cifs_fsync(struct file *, loff_t, loff_t, int);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e216bc9b7abf..ddf6f572af81 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -5275,3 +5275,19 @@ const struct address_space_operations cifs_addr_ops_smallbuf = {
.launder_folio = cifs_launder_folio,
.migrate_folio = filemap_migrate_folio,
};
+
+/*
+ * Splice data from a file into a pipe.
+ */
+ssize_t cifs_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes))
+ return 0;
+ if (unlikely(!len))
+ return 0;
+ if (in->f_flags & O_DIRECT)
+ return direct_splice_read(in, ppos, pipe, len, flags);
+ return filemap_splice_read(in, ppos, pipe, len, flags);
+}