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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-739d97d2f2csm3929268b3a.29.2025.04.04.14.44.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Apr 2025 14:44:25 -0700 (PDT) Message-ID: Date: Sat, 5 Apr 2025 08:14:20 +1030 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 1/3] btrfs: remove unnecessary early exits in delalloc folio lock and unlock To: Filipe Manana Cc: linux-btrfs@vger.kernel.org References: <39d3966f896f04c3003eb9a954ce84ff33d51345.1743731232.git.wqu@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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/4/5 02:34, Filipe Manana 写道: > On Fri, Apr 4, 2025 at 2:48 AM Qu Wenruo wrote: >> >> Inside function unlock_delalloc_folio() and lock_delalloc_folios(), we > > function -> functions > >> have the following early exist: > > exist -> exit > >> >> if (index == locked_folio->index && end_index == index) >> return; >> >> This allows us to exist early if the range are inside the same locked > > exist -> exit > the range are inside -> the range is inside > >> folio. >> >> But even without the above early check, the existing code can handle it >> well, as both __process_folios_contig() and lock_delalloc_folios() will >> skip any folio page lock/unlock if it's on the locked folio. >> >> Just remove those unnecessary early exits. > > It looks good to me from a functional point of view. > > But without this early exits there's a bit of work done, from function > calls to initializing and releasing folio batches, calling > filemap_get_folios_contig() which > will search the mapping's xarray and always grab one folio and add it > to the batch, etc. > > It's not uncommon to do IO on a range not spanning more than one > folio, especially when supporting large folios, which will be more > likely. > I understand the goal here is to remove some code, but this code is > cheaper compared to all that unnecessary overhead. > > Have you considered that? Yes, but the main reason here is the usage of (folio->index == index) check. With large folios, such check is no longer reliable anyway, and initially I thought to just change it to folio_contains(), but it turns out that is not really needed either. So that's the main reason to get rid this of these early exits. Thanks, Qu > > Thanks. > >> >> Signed-off-by: Qu Wenruo >> --- >> fs/btrfs/extent_io.c | 8 -------- >> 1 file changed, 8 deletions(-) >> >> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c >> index 8b29eeac3884..013268f70621 100644 >> --- a/fs/btrfs/extent_io.c >> +++ b/fs/btrfs/extent_io.c >> @@ -224,12 +224,7 @@ static noinline void unlock_delalloc_folio(const struct inode *inode, >> const struct folio *locked_folio, >> u64 start, u64 end) >> { >> - unsigned long index = start >> PAGE_SHIFT; >> - unsigned long end_index = end >> PAGE_SHIFT; >> - >> ASSERT(locked_folio); >> - if (index == locked_folio->index && end_index == index) >> - return; >> >> __process_folios_contig(inode->i_mapping, locked_folio, start, end, >> PAGE_UNLOCK); >> @@ -246,9 +241,6 @@ static noinline int lock_delalloc_folios(struct inode *inode, >> u64 processed_end = start; >> struct folio_batch fbatch; >> >> - if (index == locked_folio->index && index == end_index) >> - return 0; >> - >> folio_batch_init(&fbatch); >> while (index <= end_index) { >> unsigned int found_folios, i; >> -- >> 2.49.0 >> >>