[PATCH 1/2] zonefs: fix zone report size in __zonefs_io_error()

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

When an IO error occurs, the function __zonefs_io_error() is used to
issue a zone report to obtain the latest zone information from the
device. This function gets a zone report for all zones used as storage
for a file, which is always 1 zone except for files representing
aggregated conventional zones.

The number of zones of a zone report for a file is calculated in
__zonefs_io_error() by doing a bit-shift of the inode i_zone_size field,
which is equal to or larger than the device zone size. However, this
calculation does not take into account that the last zone of a zoned
device may be smaller than the zone size reported by bdev_zone_sectors()
(which is used to set the bit shift size). As a result, if an error
occurs for an IO targetting such last smaller zone, the zone report will
ask for 0 zones, leading to an invalid zone report.

Fix this by using the fact that all files require a 1 zone report,
except if the inode i_zone_size field indicates a zone size larger than
the device zone size. This exception case corresponds to aggregated
conventional zone files.

Fixes: e3c3155bc95a ("zonefs: add zone-capacity support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
---
 fs/zonefs/super.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 860f0b1032c6..f689bd3596cf 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -478,14 +478,22 @@ static void __zonefs_io_error(struct inode *inode, bool write)
 	struct super_block *sb = inode->i_sb;
 	struct zonefs_sb_info *sbi = ZONEFS_SB(sb);
 	unsigned int noio_flag;
-	unsigned int nr_zones =
-		zi->i_zone_size >> (sbi->s_zone_sectors_shift + SECTOR_SHIFT);
+	unsigned int nr_zones = 1;
 	struct zonefs_ioerr_data err = {
 		.inode = inode,
 		.write = write,
 	};
 	int ret;
 
+	/*
+	 * The only files that have more than one zone are conventional zone
+	 * files with aggregated conventional zones, for which the inode zone
+	 * size is always larger than the device zone size.
+	 */
+	if (zi->i_zone_size > bdev_zone_sectors(sb->s_bdev))
+		nr_zones = zi->i_zone_size >>
+			(sbi->s_zone_sectors_shift + SECTOR_SHIFT);
+
 	/*
 	 * Memory allocations in blkdev_report_zones() can trigger a memory
 	 * reclaim which may in turn cause a recursion into zonefs as well as
-- 
2.38.1