From 384d87ef2c954fc58e6c5fd8253e4a1984f5fe02 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 4 Sep 2020 10:58:52 +0200 Subject: block: Do not discard buffers under a mounted filesystem Discarding blocks and buffers under a mounted filesystem is hardly anything admin wants to do. Usually it will confuse the filesystem and sometimes the loss of buffer_head state (including b_private field) can even cause crashes like: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 PGD 0 P4D 0 Oops: 0002 [#1] SMP PTI CPU: 4 PID: 203778 Comm: jbd2/dm-3-8 Kdump: loaded Tainted: G O --------- - - 4.18.0-147.5.0.5.h126.eulerosv2r9.x86_64 #1 Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 1.57 08/11/2015 RIP: 0010:jbd2_journal_grab_journal_head+0x1b/0x40 [jbd2] ... Call Trace: __jbd2_journal_insert_checkpoint+0x23/0x70 [jbd2] jbd2_journal_commit_transaction+0x155f/0x1b60 [jbd2] kjournald2+0xbd/0x270 [jbd2] So if we don't have block device open with O_EXCL already, claim the block device while we truncate buffer cache. This makes sure any exclusive block device user (such as filesystem) cannot operate on the device while we are discarding buffer cache. Reported-by: Ye Bin Signed-off-by: Jan Kara Reviewed-by: Christoph Hellwig [axboe: fix !CONFIG_BLOCK error in truncate_bdev_range()] Signed-off-by: Jens Axboe --- fs/block_dev.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-) (limited to 'fs') diff --git a/fs/block_dev.c b/fs/block_dev.c index 9cb205405f9d..c70c41ecba48 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -103,6 +103,35 @@ void invalidate_bdev(struct block_device *bdev) } EXPORT_SYMBOL(invalidate_bdev); +/* + * Drop all buffers & page cache for given bdev range. This function bails + * with error if bdev has other exclusive owner (such as filesystem). + */ +int truncate_bdev_range(struct block_device *bdev, fmode_t mode, + loff_t lstart, loff_t lend) +{ + struct block_device *claimed_bdev = NULL; + int err; + + /* + * If we don't hold exclusive handle for the device, upgrade to it + * while we discard the buffer cache to avoid discarding buffers + * under live filesystem. + */ + if (!(mode & FMODE_EXCL)) { + claimed_bdev = bdev->bd_contains; + err = bd_prepare_to_claim(bdev, claimed_bdev, + truncate_bdev_range); + if (err) + return err; + } + truncate_inode_pages_range(bdev->bd_inode->i_mapping, lstart, lend); + if (claimed_bdev) + bd_abort_claiming(bdev, claimed_bdev, truncate_bdev_range); + return 0; +} +EXPORT_SYMBOL(truncate_bdev_range); + static void set_init_blocksize(struct block_device *bdev) { bdev->bd_inode->i_blkbits = blksize_bits(bdev_logical_block_size(bdev)); @@ -1968,7 +1997,6 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start, loff_t len) { struct block_device *bdev = I_BDEV(bdev_file_inode(file)); - struct address_space *mapping; loff_t end = start + len - 1; loff_t isize; int error; @@ -1996,8 +2024,9 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start, return -EINVAL; /* Invalidate the page cache, including dirty pages. */ - mapping = bdev->bd_inode->i_mapping; - truncate_inode_pages_range(mapping, start, end); + error = truncate_bdev_range(bdev, file->f_mode, start, end); + if (error) + return error; switch (mode) { case FALLOC_FL_ZERO_RANGE: @@ -2024,7 +2053,7 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start, * the caller will be given -EBUSY. The third argument is * inclusive, so the rounding here is safe. */ - return invalidate_inode_pages2_range(mapping, + return invalidate_inode_pages2_range(bdev->bd_inode->i_mapping, start >> PAGE_SHIFT, end >> PAGE_SHIFT); } -- cgit v1.2.3