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btrfs: introduce btrfs_write_check() 

btrfs_write_check() checks write parameters in one place before
beginning a write. This does away with inode_unlock() after every check.
In the later patches, it will help push inode_lock/unlock() in buffered
and direct write functions respectively.

generic_write_checks needs to be called before as it could truncate
iov_iter and its return used as count.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Goldwyn Rodrigues 2020-09-24 11:39:15 -05:00 committed by David Sterba
parent c86537a42f
commit b8d8e1fd57
1 changed files with 77 additions and 74 deletions
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151
fs/btrfs/file.c
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@ -1564,6 +1564,79 @@ void btrfs_check_nocow_unlock(struct btrfs_inode *inode)
btrfs_drew_write_unlock(&inode->root->snapshot_lock);
}
static void update_time_for_write(struct inode *inode)
{
struct timespec64 now;
if (IS_NOCMTIME(inode))
return;
now = current_time(inode);
if (!timespec64_equal(&inode->i_mtime, &now))
inode->i_mtime = now;
if (!timespec64_equal(&inode->i_ctime, &now))
inode->i_ctime = now;
if (IS_I_VERSION(inode))
inode_inc_iversion(inode);
}
static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
size_t count)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
loff_t pos = iocb->ki_pos;
int ret;
loff_t oldsize;
loff_t start_pos;
if (iocb->ki_flags & IOCB_NOWAIT) {
size_t nocow_bytes = count;
/* We will allocate space in case nodatacow is not set, so bail */
if (check_nocow_nolock(BTRFS_I(inode), pos, &nocow_bytes) <= 0)
return -EAGAIN;
/*
* There are holes in the range or parts of the range that must
* be COWed (shared extents, RO block groups, etc), so just bail
* out.
*/
if (nocow_bytes < count)
return -EAGAIN;
}
current->backing_dev_info = inode_to_bdi(inode);
ret = file_remove_privs(file);
if (ret)
return ret;
/*
* We reserve space for updating the inode when we reserve space for the
* extent we are going to write, so we will enospc out there. We don't
* need to start yet another transaction to update the inode as we will
* update the inode when we finish writing whatever data we write.
*/
update_time_for_write(inode);
start_pos = round_down(pos, fs_info->sectorsize);
oldsize = i_size_read(inode);
if (start_pos > oldsize) {
/* Expand hole size to cover write data, preventing empty gap */
loff_t end_pos = round_up(pos + count, fs_info->sectorsize);
ret = btrfs_cont_expand(inode, oldsize, end_pos);
if (ret) {
current->backing_dev_info = NULL;
return ret;
}
}
return 0;
}
static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
struct iov_iter *i)
{
@ -1873,24 +1946,6 @@ out:
return written ? written : err;
}
static void update_time_for_write(struct inode *inode)
{
struct timespec64 now;
if (IS_NOCMTIME(inode))
return;
now = current_time(inode);
if (!timespec64_equal(&inode->i_mtime, &now))
inode->i_mtime = now;
if (!timespec64_equal(&inode->i_ctime, &now))
inode->i_ctime = now;
if (IS_I_VERSION(inode))
inode_inc_iversion(inode);
}
static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
struct iov_iter *from)
{
@ -1898,14 +1953,9 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
struct inode *inode = file_inode(file);
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct btrfs_root *root = BTRFS_I(inode)->root;
u64 start_pos;
u64 end_pos;
ssize_t num_written = 0;
const bool sync = iocb->ki_flags & IOCB_DSYNC;
ssize_t err;
loff_t pos;
size_t count;
loff_t oldsize;
/*
* If the fs flips readonly due to some impossible error, although we
@ -1932,57 +1982,10 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
return err;
}
pos = iocb->ki_pos;
count = iov_iter_count(from);
if (iocb->ki_flags & IOCB_NOWAIT) {
size_t nocow_bytes = count;
/*
* We will allocate space in case nodatacow is not set,
* so bail
*/
if (check_nocow_nolock(BTRFS_I(inode), pos, &nocow_bytes)
<= 0) {
inode_unlock(inode);
return -EAGAIN;
}
/*
* There are holes in the range or parts of the range that must
* be COWed (shared extents, RO block groups, etc), so just bail
* out.
*/
if (nocow_bytes < count) {
inode_unlock(inode);
return -EAGAIN;
}
}
current->backing_dev_info = inode_to_bdi(inode);
err = file_remove_privs(file);
if (err) {
err = btrfs_write_check(iocb, from, err);
if (err < 0) {
inode_unlock(inode);
goto out;
}
/*
* We reserve space for updating the inode when we reserve space for the
* extent we are going to write, so we will enospc out there. We don't
* need to start yet another transaction to update the inode as we will
* update the inode when we finish writing whatever data we write.
*/
update_time_for_write(inode);
start_pos = round_down(pos, fs_info->sectorsize);
oldsize = i_size_read(inode);
if (start_pos > oldsize) {
/* Expand hole size to cover write data, preventing empty gap */
end_pos = round_up(pos + count,
fs_info->sectorsize);
err = btrfs_cont_expand(inode, oldsize, end_pos);
if (err) {
inode_unlock(inode);
goto out;
}
return err;
}
if (sync)
@ -2042,7 +2045,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
if (sync)
atomic_dec(&BTRFS_I(inode)->sync_writers);
out:
current->backing_dev_info = NULL;
return num_written ? num_written : err;
}