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); @@ -862,7 +896,7 @@ 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)) { @@ -904,7 +938,7 @@ 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) @@ -997,7 +1031,7 @@ 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);