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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22fc7544f81sm103624245ad.43.2025.05.14.14.01.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 May 2025 14:01:09 -0700 (PDT) Message-ID: Date: Thu, 15 May 2025 06:31:04 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] btrfs: simplify early error checking in btrfs_page_mkwrite() To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <401500c0e0108d519a4b5b5910c8678723885ed1.1747222631.git.fdmanana@suse.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <401500c0e0108d519a4b5b5910c8678723885ed1.1747222631.git.fdmanana@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/5/14 21:08, fdmanana@kernel.org 写道: > From: Filipe Manana > > 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 straighforward 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. > > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu> --- > fs/btrfs/file.c | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > index a2b1fc536fdd..9ecb9f3bd057 100644 > --- a/fs/btrfs/file.c > +++ b/fs/btrfs/file.c > @@ -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; > } >