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btrfs: Factor out write portion of btrfs_get_blocks_direct
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Now that the read side is extracted into its own function, do the same
to the write side. This leaves btrfs_get_blocks_direct_write with the
sole purpose of handling common locking required. Also flip the
condition in btrfs_get_blocks_direct_write so that the write case
comes first and we check for if (Create) rather than if (!create). This
is purely subjective but I believe makes reading a bit more "linear".
No functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Nikolay Borisov authored and David Sterba committed May 30, 2018
1 parent 1c8d017 commit c5794e5
Showing 1 changed file with 108 additions and 99 deletions.
207 changes: 108 additions & 99 deletions fs/btrfs/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7561,6 +7561,104 @@ static int btrfs_get_blocks_direct_read(struct extent_map *em,
return 0;
}

static int btrfs_get_blocks_direct_write(struct extent_map **map,
struct buffer_head *bh_result,
struct inode *inode,
struct btrfs_dio_data *dio_data,
u64 start, u64 len)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct extent_map *em = *map;
int ret = 0;

/*
* We don't allocate a new extent in the following cases
*
* 1) The inode is marked as NODATACOW. In this case we'll just use the
* existing extent.
* 2) The extent is marked as PREALLOC. We're good to go here and can
* just use the extent.
*
*/
if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
em->block_start != EXTENT_MAP_HOLE)) {
int type;
u64 block_start, orig_start, orig_block_len, ram_bytes;

if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
type = BTRFS_ORDERED_PREALLOC;
else
type = BTRFS_ORDERED_NOCOW;
len = min(len, em->len - (start - em->start));
block_start = em->block_start + (start - em->start);

if (can_nocow_extent(inode, start, &len, &orig_start,
&orig_block_len, &ram_bytes) == 1 &&
btrfs_inc_nocow_writers(fs_info, block_start)) {
struct extent_map *em2;

em2 = btrfs_create_dio_extent(inode, start, len,
orig_start, block_start,
len, orig_block_len,
ram_bytes, type);
btrfs_dec_nocow_writers(fs_info, block_start);
if (type == BTRFS_ORDERED_PREALLOC) {
free_extent_map(em);
*map = em = em2;
}

if (em2 && IS_ERR(em2)) {
ret = PTR_ERR(em2);
goto out;
}
/*
* For inode marked NODATACOW or extent marked PREALLOC,
* use the existing or preallocated extent, so does not
* need to adjust btrfs_space_info's bytes_may_use.
*/
btrfs_free_reserved_data_space_noquota(inode, start,
len);
goto skip_cow;
}
}

/* this will cow the extent */
len = bh_result->b_size;
free_extent_map(em);
*map = em = btrfs_new_extent_direct(inode, start, len);
if (IS_ERR(em)) {
ret = PTR_ERR(em);
goto out;
}

len = min(len, em->len - (start - em->start));

skip_cow:
bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
inode->i_blkbits;
bh_result->b_size = len;
bh_result->b_bdev = em->bdev;
set_buffer_mapped(bh_result);

if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
set_buffer_new(bh_result);

/*
* Need to update the i_size under the extent lock so buffered
* readers will get the updated i_size when we unlock.
*/
if (!dio_data->overwrite && start + len > i_size_read(inode))
i_size_write(inode, start + len);

WARN_ON(dio_data->reserve < len);
dio_data->reserve -= len;
dio_data->unsubmitted_oe_range_end = start + len;
current->journal_info = dio_data;
out:
return ret;
}

static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
Expand Down Expand Up @@ -7629,7 +7727,16 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
goto unlock_err;
}

if (!create) {
if (create) {
ret = btrfs_get_blocks_direct_write(&em, bh_result, inode,
dio_data, start, len);
if (ret < 0)
goto unlock_err;

/* clear and unlock the entire range */
clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
unlock_bits, 1, 0, &cached_state);
} else {
ret = btrfs_get_blocks_direct_read(em, bh_result, inode,
start, len);
/* Can be negative only if we read from a hole */
Expand All @@ -7650,106 +7757,8 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
} else {
free_extent_state(cached_state);
}
free_extent_map(em);
return 0;
}

/*
* We don't allocate a new extent in the following cases
*
* 1) The inode is marked as NODATACOW. In this case we'll just use the
* existing extent.
* 2) The extent is marked as PREALLOC. We're good to go here and can
* just use the extent.
*
*/
if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
em->block_start != EXTENT_MAP_HOLE)) {
int type;
u64 block_start, orig_start, orig_block_len, ram_bytes;

if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
type = BTRFS_ORDERED_PREALLOC;
else
type = BTRFS_ORDERED_NOCOW;
len = min(len, em->len - (start - em->start));
block_start = em->block_start + (start - em->start);

if (can_nocow_extent(inode, start, &len, &orig_start,
&orig_block_len, &ram_bytes) == 1 &&
btrfs_inc_nocow_writers(fs_info, block_start)) {
struct extent_map *em2;

em2 = btrfs_create_dio_extent(inode, start, len,
orig_start, block_start,
len, orig_block_len,
ram_bytes, type);
btrfs_dec_nocow_writers(fs_info, block_start);
if (type == BTRFS_ORDERED_PREALLOC) {
free_extent_map(em);
em = em2;
}
if (em2 && IS_ERR(em2)) {
ret = PTR_ERR(em2);
goto unlock_err;
}
/*
* For inode marked NODATACOW or extent marked PREALLOC,
* use the existing or preallocated extent, so does not
* need to adjust btrfs_space_info's bytes_may_use.
*/
btrfs_free_reserved_data_space_noquota(inode,
start, len);
goto unlock;
}
}

/*
* this will cow the extent, reset the len in case we changed
* it above
*/
len = bh_result->b_size;
free_extent_map(em);
em = btrfs_new_extent_direct(inode, start, len);
if (IS_ERR(em)) {
ret = PTR_ERR(em);
goto unlock_err;
}
len = min(len, em->len - (start - em->start));
unlock:
bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
inode->i_blkbits;
bh_result->b_size = len;
bh_result->b_bdev = em->bdev;
set_buffer_mapped(bh_result);
if (create) {
if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
set_buffer_new(bh_result);

/*
* Need to update the i_size under the extent lock so buffered
* readers will get the updated i_size when we unlock.
*/
if (!dio_data->overwrite && start + len > i_size_read(inode))
i_size_write(inode, start + len);

WARN_ON(dio_data->reserve < len);
dio_data->reserve -= len;
dio_data->unsubmitted_oe_range_end = start + len;
current->journal_info = dio_data;
}

/*
* In the case of write we need to clear and unlock the entire range,
* in the case of read we need to unlock only the end area that we
* aren't using if there is any left over space.
*/
if (lockstart < lockend) {
clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
lockend, unlock_bits, 1, 0,
&cached_state);
}
free_extent_map(em);

return 0;
Expand Down

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