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Subject[PATCH 5.18 02/11] zonefs: fix zonefs_iomap_begin() for reads
Date
From: Damien Le Moal <damien.lemoal@opensource.wdc.com>

commit c1c1204c0d0c1dccc1310b9277fb2bd8b663d8fe upstream.

If a readahead is issued to a sequential zone file with an offset
exactly equal to the current file size, the iomap type is set to
IOMAP_UNWRITTEN, which will prevent an IO, but the iomap length is
calculated as 0. This causes a WARN_ON() in iomap_iter():

[17309.548939] WARNING: CPU: 3 PID: 2137 at fs/iomap/iter.c:34 iomap_iter+0x9cf/0xe80
[...]
[17309.650907] RIP: 0010:iomap_iter+0x9cf/0xe80
[...]
[17309.754560] Call Trace:
[17309.757078] <TASK>
[17309.759240] ? lock_is_held_type+0xd8/0x130
[17309.763531] iomap_readahead+0x1a8/0x870
[17309.767550] ? iomap_read_folio+0x4c0/0x4c0
[17309.771817] ? lockdep_hardirqs_on_prepare+0x400/0x400
[17309.778848] ? lock_release+0x370/0x750
[17309.784462] ? folio_add_lru+0x217/0x3f0
[17309.790220] ? reacquire_held_locks+0x4e0/0x4e0
[17309.796543] read_pages+0x17d/0xb60
[17309.801854] ? folio_add_lru+0x238/0x3f0
[17309.807573] ? readahead_expand+0x5f0/0x5f0
[17309.813554] ? policy_node+0xb5/0x140
[17309.819018] page_cache_ra_unbounded+0x27d/0x450
[17309.825439] filemap_get_pages+0x500/0x1450
[17309.831444] ? filemap_add_folio+0x140/0x140
[17309.837519] ? lock_is_held_type+0xd8/0x130
[17309.843509] filemap_read+0x28c/0x9f0
[17309.848953] ? zonefs_file_read_iter+0x1ea/0x4d0 [zonefs]
[17309.856162] ? trace_contention_end+0xd6/0x130
[17309.862416] ? __mutex_lock+0x221/0x1480
[17309.868151] ? zonefs_file_read_iter+0x166/0x4d0 [zonefs]
[17309.875364] ? filemap_get_pages+0x1450/0x1450
[17309.881647] ? __mutex_unlock_slowpath+0x15e/0x620
[17309.888248] ? wait_for_completion_io_timeout+0x20/0x20
[17309.895231] ? lock_is_held_type+0xd8/0x130
[17309.901115] ? lock_is_held_type+0xd8/0x130
[17309.906934] zonefs_file_read_iter+0x356/0x4d0 [zonefs]
[17309.913750] new_sync_read+0x2d8/0x520
[17309.919035] ? __x64_sys_lseek+0x1d0/0x1d0

Furthermore, this causes iomap_readahead() to loop forever as
iomap_readahead_iter() always returns 0, making no progress.

Fix this by treating reads after the file size as access to holes,
setting the iomap type to IOMAP_HOLE, the iomap addr to IOMAP_NULL_ADDR
and using the length argument as is for the iomap length. To simplify
the code with this change, zonefs_iomap_begin() is split into the read
variant, zonefs_read_iomap_begin() and zonefs_read_iomap_ops, and the
write variant, zonefs_write_iomap_begin() and zonefs_write_iomap_ops.

Reported-by: Jorgen Hansen <Jorgen.Hansen@wdc.com>
Fixes: 8dcc1a9d90c1 ("fs: New zonefs file system")
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Jorgen Hansen <Jorgen.Hansen@wdc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/zonefs/super.c | 94 ++++++++++++++++++++++++++++++++++++------------------
1 file changed, 64 insertions(+), 30 deletions(-)

--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -72,15 +72,51 @@ static inline void zonefs_i_size_write(s
zi->i_flags &= ~ZONEFS_ZONE_OPEN;
}

-static int zonefs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
- unsigned int flags, struct iomap *iomap,
- struct iomap *srcmap)
+static int zonefs_read_iomap_begin(struct inode *inode, loff_t offset,
+ loff_t length, unsigned int flags,
+ struct iomap *iomap, struct iomap *srcmap)
{
struct zonefs_inode_info *zi = ZONEFS_I(inode);
struct super_block *sb = inode->i_sb;
loff_t isize;

- /* All I/Os should always be within the file maximum size */
+ /*
+ * All blocks are always mapped below EOF. If reading past EOF,
+ * act as if there is a hole up to the file maximum size.
+ */
+ mutex_lock(&zi->i_truncate_mutex);
+ iomap->bdev = inode->i_sb->s_bdev;
+ iomap->offset = ALIGN_DOWN(offset, sb->s_blocksize);
+ isize = i_size_read(inode);
+ if (iomap->offset >= isize) {
+ iomap->type = IOMAP_HOLE;
+ iomap->addr = IOMAP_NULL_ADDR;
+ iomap->length = length;
+ } else {
+ iomap->type = IOMAP_MAPPED;
+ iomap->addr = (zi->i_zsector << SECTOR_SHIFT) + iomap->offset;
+ iomap->length = isize - iomap->offset;
+ }
+ mutex_unlock(&zi->i_truncate_mutex);
+
+ trace_zonefs_iomap_begin(inode, iomap);
+
+ return 0;
+}
+
+static const struct iomap_ops zonefs_read_iomap_ops = {
+ .iomap_begin = zonefs_read_iomap_begin,
+};
+
+static int zonefs_write_iomap_begin(struct inode *inode, loff_t offset,
+ loff_t length, unsigned int flags,
+ struct iomap *iomap, struct iomap *srcmap)
+{
+ struct zonefs_inode_info *zi = ZONEFS_I(inode);
+ struct super_block *sb = inode->i_sb;
+ loff_t isize;
+
+ /* All write I/Os should always be within the file maximum size */
if (WARN_ON_ONCE(offset + length > zi->i_max_size))
return -EIO;

@@ -90,7 +126,7 @@ static int zonefs_iomap_begin(struct ino
* operation.
*/
if (WARN_ON_ONCE(zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
- (flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT)))
+ !(flags & IOMAP_DIRECT)))
return -EIO;

/*
@@ -99,47 +135,44 @@ static int zonefs_iomap_begin(struct ino
* write pointer) and unwriten beyond.
*/
mutex_lock(&zi->i_truncate_mutex);
+ iomap->bdev = inode->i_sb->s_bdev;
+ iomap->offset = ALIGN_DOWN(offset, sb->s_blocksize);
+ iomap->addr = (zi->i_zsector << SECTOR_SHIFT) + iomap->offset;
isize = i_size_read(inode);
- if (offset >= isize)
+ if (iomap->offset >= isize) {
iomap->type = IOMAP_UNWRITTEN;
- else
+ iomap->length = zi->i_max_size - iomap->offset;
+ } else {
iomap->type = IOMAP_MAPPED;
- if (flags & IOMAP_WRITE)
- length = zi->i_max_size - offset;
- else
- length = min(length, isize - offset);
+ iomap->length = isize - iomap->offset;
+ }
mutex_unlock(&zi->i_truncate_mutex);

- iomap->offset = ALIGN_DOWN(offset, sb->s_blocksize);
- iomap->length = ALIGN(offset + length, sb->s_blocksize) - iomap->offset;
- iomap->bdev = inode->i_sb->s_bdev;
- iomap->addr = (zi->i_zsector << SECTOR_SHIFT) + iomap->offset;
-
trace_zonefs_iomap_begin(inode, iomap);

return 0;
}

-static const struct iomap_ops zonefs_iomap_ops = {
- .iomap_begin = zonefs_iomap_begin,
+static const struct iomap_ops zonefs_write_iomap_ops = {
+ .iomap_begin = zonefs_write_iomap_begin,
};

static int zonefs_readpage(struct file *unused, struct page *page)
{
- return iomap_readpage(page, &zonefs_iomap_ops);
+ return iomap_readpage(page, &zonefs_read_iomap_ops);
}

static void zonefs_readahead(struct readahead_control *rac)
{
- iomap_readahead(rac, &zonefs_iomap_ops);
+ iomap_readahead(rac, &zonefs_read_iomap_ops);
}

/*
* Map blocks for page writeback. This is used only on conventional zone files,
* which implies that the page range can only be within the fixed inode size.
*/
-static int zonefs_map_blocks(struct iomap_writepage_ctx *wpc,
- struct inode *inode, loff_t offset)
+static int zonefs_write_map_blocks(struct iomap_writepage_ctx *wpc,
+ struct inode *inode, loff_t offset)
{
struct zonefs_inode_info *zi = ZONEFS_I(inode);

@@ -153,12 +186,12 @@ static int zonefs_map_blocks(struct ioma
offset < wpc->iomap.offset + wpc->iomap.length)
return 0;

- return zonefs_iomap_begin(inode, offset, zi->i_max_size - offset,
- IOMAP_WRITE, &wpc->iomap, NULL);
+ return zonefs_write_iomap_begin(inode, offset, zi->i_max_size - offset,
+ IOMAP_WRITE, &wpc->iomap, NULL);
}

static const struct iomap_writeback_ops zonefs_writeback_ops = {
- .map_blocks = zonefs_map_blocks,
+ .map_blocks = zonefs_write_map_blocks,
};

static int zonefs_writepage(struct page *page, struct writeback_control *wbc)
@@ -188,7 +221,8 @@ static int zonefs_swap_activate(struct s
return -EINVAL;
}

- return iomap_swapfile_activate(sis, swap_file, span, &zonefs_iomap_ops);
+ return iomap_swapfile_activate(sis, swap_file, span,
+ &zonefs_read_iomap_ops);
}

static const struct address_space_operations zonefs_file_aops = {
@@ -607,7 +641,7 @@ static vm_fault_t zonefs_filemap_page_mk

/* Serialize against truncates */
filemap_invalidate_lock_shared(inode->i_mapping);
- ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
+ ret = iomap_page_mkwrite(vmf, &zonefs_write_iomap_ops);
filemap_invalidate_unlock_shared(inode->i_mapping);

sb_end_pagefault(inode->i_sb);
@@ -860,7 +894,7 @@ static ssize_t zonefs_file_dio_write(str
if (append)
ret = zonefs_file_dio_append(iocb, from);
else
- ret = iomap_dio_rw(iocb, from, &zonefs_iomap_ops,
+ ret = iomap_dio_rw(iocb, from, &zonefs_write_iomap_ops,
&zonefs_write_dio_ops, 0, 0);
if (zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
(ret > 0 || ret == -EIOCBQUEUED)) {
@@ -902,7 +936,7 @@ static ssize_t zonefs_file_buffered_writ
if (ret <= 0)
goto inode_unlock;

- ret = iomap_file_buffered_write(iocb, from, &zonefs_iomap_ops);
+ ret = iomap_file_buffered_write(iocb, from, &zonefs_write_iomap_ops);
if (ret > 0)
iocb->ki_pos += ret;
else if (ret == -EIO)
@@ -995,7 +1029,7 @@ static ssize_t zonefs_file_read_iter(str
goto inode_unlock;
}
file_accessed(iocb->ki_filp);
- ret = iomap_dio_rw(iocb, to, &zonefs_iomap_ops,
+ ret = iomap_dio_rw(iocb, to, &zonefs_read_iomap_ops,
&zonefs_read_dio_ops, 0, 0);
} else {
ret = generic_file_read_iter(iocb, to);

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