xfs: xfs_seek_hole() refinement with hole searching from page cache for unwritten extents (b686d1f7) · Commits · e / devices / android_kernel_oneplus_sm8150

fs/xfs/xfs_file.c

+67 −11

Original line number	Diff line number	Diff line
		@@ -1289,9 +1289,9 @@ xfs_seek_hole(
		struct xfs_inode *ip = XFS_I(inode);
		struct xfs_mount *mp = ip->i_mount;
		loff_t uninitialized_var(offset);
		loff_t holeoff;
		xfs_fsize_t isize;
		xfs_fileoff_t fsbno;
		xfs_filblks_t end;
		uint lock;
		int error;

		@@ -1307,21 +1307,77 @@ xfs_seek_hole(
		}

		fsbno = XFS_B_TO_FSBT(mp, start);
		error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);
		end = XFS_B_TO_FSB(mp, isize);

		for (;;) {
		struct xfs_bmbt_irec map[2];
		int nmap = 2;
		unsigned int i;

		error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
		XFS_BMAPI_ENTIRE);
		if (error)
		goto out_unlock;

		holeoff = XFS_FSB_TO_B(mp, fsbno);
		if (holeoff <= start)
		offset = start;
		else {
		/* No extents at given offset, must be beyond EOF */
		if (nmap == 0) {
		error = ENXIO;
		goto out_unlock;
		}

		for (i = 0; i < nmap; i++) {
		offset = max_t(loff_t, start,
		XFS_FSB_TO_B(mp, map[i].br_startoff));

		/* Landed in a hole */
		if (map[i].br_startblock == HOLESTARTBLOCK)
		goto out;

		/*
		* xfs_bmap_first_unused() could return a value bigger than
		* isize if there are no more holes past the supplied offset.
		* Landed in an unwritten extent, try to search hole
		* from page cache.
		*/
		offset = min_t(loff_t, holeoff, isize);
		if (map[i].br_state == XFS_EXT_UNWRITTEN) {
		if (xfs_find_get_desired_pgoff(inode, &map[i],
		HOLE_OFF, &offset))
		goto out;
		}
		}

		/*
		* map[0] contains data or its unwritten but contains
		* data in page cache, probably means that we are
		* reading after EOF. We should fix offset to point
		* to the end of the file(i.e., there is an implicit
		* hole at the end of any file).
		*/
		if (nmap == 1) {
		offset = isize;
		break;
		}

		ASSERT(i > 1);

		/*
		* Both mappings contains data, proceed to the next round of
		* search if the current reading offset not beyond or hit EOF.
		*/
		fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
		start = XFS_FSB_TO_B(mp, fsbno);
		if (start >= isize) {
		offset = isize;
		break;
		}
		}

		out:
		/*
		* At this point, we must have found a hole. However, the returned
		* offset may be bigger than the file size as it may be aligned to
		* page boundary for unwritten extents, we need to deal with this
		* situation in particular.
		*/
		offset = min_t(loff_t, offset, isize);
		if (offset != file->f_pos)
		file->f_pos = offset;