linux-kernel - [PATCH 4/5] nilfs2: do not propagate ENOENT error from sufile during GC

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Message-Id: <20240821154627.11848-5-konishi.ryusuke@gmail.com>
Date: Thu, 22 Aug 2024 00:46:26 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-nilfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] nilfs2: do not propagate ENOENT error from sufile during GC

nilfs_sufile_freev(), which is used to free segments in GC, aborts with
-ENOENT if the target segment usage is on a hole block.

This error only occurs if one of the segment numbers to be freed passed
by the GC ioctl is invalid, so return -EINVAL instead.

To avoid impairing readability, introduce a wrapper function that
encapsulates error handling including the error code conversion (and
error message output).

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@...il.com>
---
 fs/nilfs2/segment.c | 64 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 56 insertions(+), 8 deletions(-)

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 871ec35ea8e8..765d55333a13 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1102,12 +1102,64 @@ static int nilfs_segctor_scan_file_dsync(struct nilfs_sc_info *sci,
 	return err;
 }
 
+/**
+ * nilfs_free_segments - free the segments given by an array of segment numbers
+ * @nilfs:   nilfs object
+ * @segnumv: array of segment numbers to be freed
+ * @nsegs:   number of segments to be freed in @segnumv
+ *
+ * nilfs_free_segments() wraps nilfs_sufile_freev() and
+ * nilfs_sufile_cancel_freev(), and edits the segment usage metadata file
+ * (sufile) to free all segments given by @segnumv and @nsegs at once.  If
+ * it fails midway, it cancels the changes so that none of the segments are
+ * freed.  If @nsegs is 0, this function does nothing.
+ *
+ * The freeing of segments is not finalized until the writing of a log with
+ * a super root block containing this sufile change is complete, and it can
+ * be canceled with nilfs_sufile_cancel_freev() until then.
+ *
+ * Return: 0 on success, or the following negative error code on failure.
+ * * %-EINVAL	- Invalid segment number.
+ * * %-EIO	- I/O error (including metadata corruption).
+ * * %-ENOMEM	- Insufficient memory available.
+ */
+static int nilfs_free_segments(struct the_nilfs *nilfs, __u64 *segnumv,
+			       size_t nsegs)
+{
+	size_t ndone;
+	int ret;
+
+	if (!nsegs)
+		return 0;
+
+	ret = nilfs_sufile_freev(nilfs->ns_sufile, segnumv, nsegs, &ndone);
+	if (unlikely(ret)) {
+		nilfs_sufile_cancel_freev(nilfs->ns_sufile, segnumv, ndone,
+					  NULL);
+		/*
+		 * If a segment usage of the segments to be freed is in a
+		 * hole block, nilfs_sufile_freev() will return -ENOENT.
+		 * In this case, -EINVAL should be returned to the caller
+		 * since there is something wrong with the given segment
+		 * number array.  This error can only occur during GC, so
+		 * there is no need to worry about it propagating to other
+		 * callers (such as fsync).
+		 */
+		if (ret == -ENOENT) {
+			nilfs_err(nilfs->ns_sb,
+				  "The segment usage entry %llu to be freed is invalid (in a hole)",
+				  (unsigned long long)segnumv[ndone]);
+			ret = -EINVAL;
+		}
+	}
+	return ret;
+}
+
 static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
 {
 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
 	struct list_head *head;
 	struct nilfs_inode_info *ii;
-	size_t ndone;
 	int err = 0;
 
 	switch (nilfs_sc_cstage_get(sci)) {
@@ -1201,14 +1253,10 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
 		nilfs_sc_cstage_inc(sci);
 		fallthrough;
 	case NILFS_ST_SUFILE:
-		err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
-					 sci->sc_nfreesegs, &ndone);
-		if (unlikely(err)) {
-			nilfs_sufile_cancel_freev(nilfs->ns_sufile,
-						  sci->sc_freesegs, ndone,
-						  NULL);
+		err = nilfs_free_segments(nilfs, sci->sc_freesegs,
+					  sci->sc_nfreesegs);
+		if (unlikely(err))
 			break;
-		}
 		sci->sc_stage.flags |= NILFS_CF_SUFREED;
 
 		err = nilfs_segctor_scan_file(sci, nilfs->ns_sufile,
-- 
2.34.1