On 5.09.23 11:59, Andrey Zhadchenko wrote:
Add new function for block_device_operations, which will be used
for SEEK_HOLE and SEEK_DATA llseek calls
Feature: dm: implement SEEK_HOLE for dm-qcow2 and dm-ploop
https://jira.vzint.dev/browse/PSBM-145746
Signed-off-by: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com>
---
v2: fix critical bug: do not (SEEK_HOLE | SEEK_DATA) as they are
rather continious enums
v3: add new helper to handle edge cases
block/fops.c | 38 ++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 1 +
2 files changed, 39 insertions(+)
diff --git a/block/fops.c b/block/fops.c
index 0d07e6f6b284..edd97923a7f1 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -424,6 +424,31 @@ const struct address_space_operations def_blk_aops = {
.is_dirty_writeback = buffer_check_dirty_writeback,
};
+static loff_t blkdev_llseek_wrapper(struct block_device *bdev, loff_t offset, int whence)
+{
+ loff_t retval, bd_size;
+
+ bd_size = i_size_read(bdev->bd_inode);
+ if (offset >= bd_size)
+ return -ENXIO;
+
+ retval = bdev->bd_disk->fops->llseek_hole(bdev, offset, whence);
+ if (retval < 0)
+ return retval;
+
+ if (retval < offset)
+ retval = offset;
+
+ if (retval >= bd_size) {
+ if (whence & SEEK_DATA)
+ retval = -ENXIO;
+ if (whence & SEEK_HOLE)
+ retval = bd_size;
+ }
+
+ return retval;
+}
+
/*
* for a block special file file_inode(file)->i_size is zero
* so we compute the size by hand (just as in block_read/write above)
@@ -431,11 +456,24 @@ const struct address_space_operations def_blk_aops = {
static loff_t blkdev_llseek(struct file *file, loff_t offset, int whence)
{
struct inode *bd_inode = bdev_file_inode(file);
+ struct block_device *bdev = I_BDEV(bd_inode);
+ bool is_llseek_hole;
loff_t retval;
+ is_llseek_hole = (whence == SEEK_HOLE || whence == SEEK_DATA);
+ if (is_llseek_hole && bdev->bd_disk->fops->llseek_hole) {
+ retval = blkdev_llseek_wrapper(bdev, offset, whence);
+ if (retval < 0)
+ return retval;
+
+ offset = retval;
+ whence = SEEK_SET;
+ }
+
inode_lock(bd_inode);
retval = fixed_size_llseek(file, offset, whence, i_size_read(bd_inode));
inode_unlock(bd_inode);
+
return retval;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8b82a63500fc..5c10935cb38e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1482,6 +1482,7 @@ struct block_device_operations {
int (*getgeo)(struct block_device *, struct hd_geometry *);
int (*set_read_only)(struct block_device *bdev, bool ro);
void (*free_disk)(struct gendisk *disk);
+ loff_t (*llseek_hole)(struct block_device *bdev, loff_t offset, int
whence);
/* this callback is with swap_lock and sometimes page table lock held */
void (*swap_slot_free_notify) (struct block_device *, unsigned long);
int (*report_zones)(struct gendisk *, sector_t sector,
LGTM
--
Regards,
Alexander Atanasov
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