zonefs: Provide a splice-read wrapper

Provide a splice_read wrapper for zonefs.  This does some checks before
proceeding and locks the inode across the call to filemap_splice_read() and
a size check in case of truncation.  Splicing from direct I/O is handled by
the caller.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Darrick J. Wong <djwong@kernel.org>
cc: linux-xfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-mm@kvack.org
Acked-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230522135018.2742245-26-dhowells@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
index 132f01d..65d4c4f 100644 (file)
--- a/fs/zonefs/file.c
+++ b/fs/zonefs/file.c
@@ -752,6 +752,44 @@ inode_unlock:
        return ret;
 }
 
+static ssize_t zonefs_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 zonefs_inode_info *zi = ZONEFS_I(inode);
+       struct zonefs_zone *z = zonefs_inode_zone(inode);
+       loff_t isize;
+       ssize_t ret = 0;
+
+       /* Offline zones cannot be read */
+       if (unlikely(IS_IMMUTABLE(inode) && !(inode->i_mode & 0777)))
+               return -EPERM;
+
+       if (*ppos >= z->z_capacity)
+               return 0;
+
+       inode_lock_shared(inode);
+
+       /* Limit read operations to written data */
+       mutex_lock(&zi->i_truncate_mutex);
+       isize = i_size_read(inode);
+       if (*ppos >= isize)
+               len = 0;
+       else
+               len = min_t(loff_t, len, isize - *ppos);
+       mutex_unlock(&zi->i_truncate_mutex);
+
+       if (len > 0) {
+               ret = filemap_splice_read(in, ppos, pipe, len, flags);
+               if (ret == -EIO)
+                       zonefs_io_error(inode, false);
+       }
+
+       inode_unlock_shared(inode);
+       return ret;
+}
+
 /*
  * Write open accounting is done only for sequential files.
  */
@@ -896,7 +934,7 @@ const struct file_operations zonefs_file_operations = {
        .llseek         = zonefs_file_llseek,
        .read_iter      = zonefs_file_read_iter,
        .write_iter     = zonefs_file_write_iter,
-       .splice_read    = generic_file_splice_read,
+       .splice_read    = zonefs_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .iopoll         = iocb_bio_iopoll,
 };