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authorLinus Torvalds <torvalds@linux-foundation.org>2023-06-26 21:52:12 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2023-06-26 21:52:12 +0300
commit3eccc0c886b1796f95a289c9d127c8ca1a254bd5 (patch)
tree021761894d246df22d53e1c64810f6cbf3ece716 /mm
parentcc423f6337d0a5ff1906f3b3d465d28c0d1705f6 (diff)
parent9eee8bd81421c5e961cbb1a3c3fa1a06fad545e8 (diff)
downloadlinux-3eccc0c886b1796f95a289c9d127c8ca1a254bd5.tar.xz
Merge tag 'for-6.5/splice-2023-06-23' of git://git.kernel.dk/linux
Pull splice updates from Jens Axboe: "This kills off ITER_PIPE to avoid a race between truncate, iov_iter_revert() on the pipe and an as-yet incomplete DMA to a bio with unpinned/unref'ed pages from an O_DIRECT splice read. This causes memory corruption. Instead, we either use (a) filemap_splice_read(), which invokes the buffered file reading code and splices from the pagecache into the pipe; (b) copy_splice_read(), which bulk-allocates a buffer, reads into it and then pushes the filled pages into the pipe; or (c) handle it in filesystem-specific code. Summary: - Rename direct_splice_read() to copy_splice_read() - Simplify the calculations for the number of pages to be reclaimed in copy_splice_read() - Turn do_splice_to() into a helper, vfs_splice_read(), so that it can be used by overlayfs and coda to perform the checks on the lower fs - Make vfs_splice_read() jump to copy_splice_read() to handle direct-I/O and DAX - Provide shmem with its own splice_read to handle non-existent pages in the pagecache. We don't want a ->read_folio() as we don't want to populate holes, but filemap_get_pages() requires it - Provide overlayfs with its own splice_read to call down to a lower layer as overlayfs doesn't provide ->read_folio() - Provide coda with its own splice_read to call down to a lower layer as coda doesn't provide ->read_folio() - Direct ->splice_read to copy_splice_read() in tty, procfs, kernfs and random files as they just copy to the output buffer and don't splice pages - Provide wrappers for afs, ceph, ecryptfs, ext4, f2fs, nfs, ntfs3, ocfs2, orangefs, xfs and zonefs to do locking and/or revalidation - Make cifs use filemap_splice_read() - Replace pointers to generic_file_splice_read() with pointers to filemap_splice_read() as DIO and DAX are handled in the caller; filesystems can still provide their own alternate ->splice_read() op - Remove generic_file_splice_read() - Remove ITER_PIPE and its paraphernalia as generic_file_splice_read was the only user" * tag 'for-6.5/splice-2023-06-23' of git://git.kernel.dk/linux: (31 commits) splice: kdoc for filemap_splice_read() and copy_splice_read() iov_iter: Kill ITER_PIPE splice: Remove generic_file_splice_read() splice: Use filemap_splice_read() instead of generic_file_splice_read() cifs: Use filemap_splice_read() trace: Convert trace/seq to use copy_splice_read() zonefs: Provide a splice-read wrapper xfs: Provide a splice-read wrapper orangefs: Provide a splice-read wrapper ocfs2: Provide a splice-read wrapper ntfs3: Provide a splice-read wrapper nfs: Provide a splice-read wrapper f2fs: Provide a splice-read wrapper ext4: Provide a splice-read wrapper ecryptfs: Provide a splice-read wrapper ceph: Provide a splice-read wrapper afs: Provide a splice-read wrapper 9p: Add splice_read wrapper net: Make sock_splice_read() use copy_splice_read() by default tty, proc, kernfs, random: Use copy_splice_read() ...
Diffstat (limited to 'mm')
-rw-r--r--mm/filemap.c31
-rw-r--r--mm/shmem.c134
2 files changed, 157 insertions, 8 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 83dda76d1fc3..00f01d8ead47 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2693,8 +2693,7 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(iocb->ki_pos >= i_size_read(inode)))
break;
- error = filemap_get_pages(iocb, iter->count, &fbatch,
- iov_iter_is_pipe(iter));
+ error = filemap_get_pages(iocb, iter->count, &fbatch, false);
if (error < 0)
break;
@@ -2878,9 +2877,24 @@ size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
return spliced;
}
-/*
- * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into
- * a pipe.
+/**
+ * filemap_splice_read - Splice data from a file's pagecache into a pipe
+ * @in: The file to read from
+ * @ppos: Pointer to the file position to read from
+ * @pipe: The pipe to splice into
+ * @len: The amount to splice
+ * @flags: The SPLICE_F_* flags
+ *
+ * This function gets folios from a file's pagecache and splices them into the
+ * pipe. Readahead will be called as necessary to fill more folios. This may
+ * be used for blockdevs also.
+ *
+ * Return: On success, the number of bytes read will be returned and *@ppos
+ * will be updated if appropriate; 0 will be returned if there is no more data
+ * to be read; -EAGAIN will be returned if the pipe had no space, and some
+ * other negative error code will be returned on error. A short read may occur
+ * if the pipe has insufficient space, we reach the end of the data or we hit a
+ * hole.
*/
ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe,
@@ -2893,6 +2907,9 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
bool writably_mapped;
int i, error = 0;
+ if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
+ return 0;
+
init_sync_kiocb(&iocb, in);
iocb.ki_pos = *ppos;
@@ -2906,7 +2923,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
do {
cond_resched();
- if (*ppos >= i_size_read(file_inode(in)))
+ if (*ppos >= i_size_read(in->f_mapping->host))
break;
iocb.ki_pos = *ppos;
@@ -2922,7 +2939,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
* part of the page is not copied back to userspace (unless
* another truncate extends the file - this is desired though).
*/
- isize = i_size_read(file_inode(in));
+ isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
break;
end_offset = min_t(loff_t, isize, *ppos + len);
diff --git a/mm/shmem.c b/mm/shmem.c
index e40a08c5c6d7..1f504ed982cf 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2731,6 +2731,138 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
return retval ? retval : error;
}
+static bool zero_pipe_buf_get(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return true;
+}
+
+static void zero_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+}
+
+static bool zero_pipe_buf_try_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return false;
+}
+
+static const struct pipe_buf_operations zero_pipe_buf_ops = {
+ .release = zero_pipe_buf_release,
+ .try_steal = zero_pipe_buf_try_steal,
+ .get = zero_pipe_buf_get,
+};
+
+static size_t splice_zeropage_into_pipe(struct pipe_inode_info *pipe,
+ loff_t fpos, size_t size)
+{
+ size_t offset = fpos & ~PAGE_MASK;
+
+ size = min_t(size_t, size, PAGE_SIZE - offset);
+
+ if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
+ struct pipe_buffer *buf = pipe_head_buf(pipe);
+
+ *buf = (struct pipe_buffer) {
+ .ops = &zero_pipe_buf_ops,
+ .page = ZERO_PAGE(0),
+ .offset = offset,
+ .len = size,
+ };
+ pipe->head++;
+ }
+
+ return size;
+}
+
+static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe,
+ size_t len, unsigned int flags)
+{
+ struct inode *inode = file_inode(in);
+ struct address_space *mapping = inode->i_mapping;
+ struct folio *folio = NULL;
+ size_t total_spliced = 0, used, npages, n, part;
+ loff_t isize;
+ int error = 0;
+
+ /* Work out how much data we can actually add into the pipe */
+ used = pipe_occupancy(pipe->head, pipe->tail);
+ npages = max_t(ssize_t, pipe->max_usage - used, 0);
+ len = min_t(size_t, len, npages * PAGE_SIZE);
+
+ do {
+ if (*ppos >= i_size_read(inode))
+ break;
+
+ error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio, SGP_READ);
+ if (error) {
+ if (error == -EINVAL)
+ error = 0;
+ break;
+ }
+ if (folio) {
+ folio_unlock(folio);
+
+ if (folio_test_hwpoison(folio)) {
+ error = -EIO;
+ break;
+ }
+ }
+
+ /*
+ * i_size must be checked after we know the pages are Uptodate.
+ *
+ * Checking i_size after the check allows us to calculate
+ * the correct value for "nr", which means the zero-filled
+ * part of the page is not copied back to userspace (unless
+ * another truncate extends the file - this is desired though).
+ */
+ isize = i_size_read(inode);
+ if (unlikely(*ppos >= isize))
+ break;
+ part = min_t(loff_t, isize - *ppos, len);
+
+ if (folio) {
+ /*
+ * If users can be writing to this page using arbitrary
+ * virtual addresses, take care about potential aliasing
+ * before reading the page on the kernel side.
+ */
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_folio(folio);
+ folio_mark_accessed(folio);
+ /*
+ * Ok, we have the page, and it's up-to-date, so we can
+ * now splice it into the pipe.
+ */
+ n = splice_folio_into_pipe(pipe, folio, *ppos, part);
+ folio_put(folio);
+ folio = NULL;
+ } else {
+ n = splice_zeropage_into_pipe(pipe, *ppos, len);
+ }
+
+ if (!n)
+ break;
+ len -= n;
+ total_spliced += n;
+ *ppos += n;
+ in->f_ra.prev_pos = *ppos;
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ break;
+
+ cond_resched();
+ } while (len);
+
+ if (folio)
+ folio_put(folio);
+
+ file_accessed(in);
+ return total_spliced ? total_spliced : error;
+}
+
static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
{
struct address_space *mapping = file->f_mapping;
@@ -3971,7 +4103,7 @@ static const struct file_operations shmem_file_operations = {
.read_iter = shmem_file_read_iter,
.write_iter = generic_file_write_iter,
.fsync = noop_fsync,
- .splice_read = generic_file_splice_read,
+ .splice_read = shmem_file_splice_read,
.splice_write = iter_file_splice_write,
.fallocate = shmem_fallocate,
#endif