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btrfs: simplify early error checking in btrfs_page_mkwrite()

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We have this entangled error checks early at btrfs_page_mkwrite():

1) Try to reserve delalloc space by calling btrfs_delalloc_reserve_space()
   and storing the return value in the ret2 variable;

2) If the reservation succeed, call file_update_time() and store the
   return value in ret2 and also set the local variable 'reserved' to
   true (1);

3) Then do an error check on ret2 to see if any of the previous calls
   failed and if so, jump either to the 'out' label or to the
   'out_noreserve' label, depending on whether 'reserved' is true or
   not.

This is unnecessarily complex. Instead change this to a simpler and
more straightforward approach:

1) Call btrfs_delalloc_reserve_space(), if that returns an error jump to
   the 'out_noreserve' label;

2) The call file_update_time() and if that returns an error jump to the
   'out' label.

Like this there's less nested if statements, no need to use a local
variable to track if space was reserved and if statements are used only
to check errors.

Also move the call to extent_changeset_free() out of the 'out_noreserve'
label and under the 'out' label  since the changeset is allocated only if
the call to reserve delalloc space succeeded.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2025-05-13 10:27:44 +01:00 committed by David Sterba
parent bf1c74ccba
commit a08625f825
1 changed files with 7 additions and 8 deletions
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15
fs/btrfs/file.c
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@ -1843,7 +1843,6 @@ static vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
size_t fsize = folio_size(folio);
vm_fault_t ret;
int ret2;
int reserved = 0;
u64 reserved_space;
u64 page_start;
u64 page_end;
@ -1866,17 +1865,17 @@ static vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
*/
ret2 = btrfs_delalloc_reserve_space(BTRFS_I(inode), &data_reserved,
page_start, reserved_space);
if (!ret2) {
ret2 = file_update_time(vmf->vma->vm_file);
reserved = 1;
}
if (ret2) {
ret = vmf_error(ret2);
if (reserved)
goto out;
goto out_noreserve;
}
ret2 = file_update_time(vmf->vma->vm_file);
if (ret2) {
ret = vmf_error(ret2);
goto out;
}
/* Make the VM retry the fault. */
ret = VM_FAULT_NOPAGE;
again:
@ -1972,9 +1971,9 @@ static vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
btrfs_delalloc_release_extents(BTRFS_I(inode), fsize);
btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved, page_start,
reserved_space, true);
extent_changeset_free(data_reserved);
out_noreserve:
sb_end_pagefault(inode->i_sb);
extent_changeset_free(data_reserved);
return ret;
}