xfs: enable discarding of folios backing an xfile

Create a new xfile function to discard the page cache that's backing
part of an xfile.  The next patch wil use this to drop parts of an xfile
that aren't needed anymore.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 8d05f2a..7d07912 100644 (file)
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -948,6 +948,7 @@ DEFINE_XFILE_EVENT(xfile_store);
 DEFINE_XFILE_EVENT(xfile_seek_data);
 DEFINE_XFILE_EVENT(xfile_get_folio);
 DEFINE_XFILE_EVENT(xfile_put_folio);
+DEFINE_XFILE_EVENT(xfile_discard);
 
 TRACE_EVENT(xfarray_create,
        TP_PROTO(struct xfarray *xfa, unsigned long long required_capacity),

diff --git a/fs/xfs/scrub/xfile.c b/fs/xfs/scrub/xfile.c
index 8cdd863..4e254a0 100644 (file)
--- a/fs/xfs/scrub/xfile.c
+++ b/fs/xfs/scrub/xfile.c
@@ -310,3 +310,15 @@ xfile_put_folio(
        folio_unlock(folio);
        folio_put(folio);
 }
+
+/* Discard the page cache that's backing a range of the xfile. */
+void
+xfile_discard(
+       struct xfile            *xf,
+       loff_t                  pos,
+       u64                     count)
+{
+       trace_xfile_discard(xf, pos, count);
+
+       shmem_truncate_range(file_inode(xf->file), pos, pos + count - 1);
+}

diff --git a/fs/xfs/scrub/xfile.h b/fs/xfs/scrub/xfile.h
index 76d78db..8dfbae1 100644 (file)
--- a/fs/xfs/scrub/xfile.h
+++ b/fs/xfs/scrub/xfile.h
@@ -17,6 +17,7 @@ int xfile_load(struct xfile *xf, void *buf, size_t count, loff_t pos);
 int xfile_store(struct xfile *xf, const void *buf, size_t count,
                loff_t pos);
 
+void xfile_discard(struct xfile *xf, loff_t pos, u64 count);
 loff_t xfile_seek_data(struct xfile *xf, loff_t pos);
 
 #define XFILE_MAX_FOLIO_SIZE   (PAGE_SIZE << MAX_PAGECACHE_ORDER)