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b=RtkwtDPA5zNK7X9fng3o5Z0AbVRyNRYkIWBdIP27cDWFoo9q5cVei7/drfUUt7542fOUa+QVg9eRX6nE86wFLJnEhmiq0Tw2/TmW2mvLzhA9S1cpzMnS8kbyPoU8k0NlpzXwIHodBX8300kPAYoS+Zp5+6Eq6U5HtfxFsJpFOgA= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WHH-UDB_1729073378 cluster:ay36) by smtp.aliyun-inc.com; Wed, 16 Oct 2024 18:09:39 +0800 From: Baolin Wang To: akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, david@redhat.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mm: shmem: update iocb->ki_pos directly to simplify tmpfs read logic Date: Wed, 16 Oct 2024 18:09:29 +0800 Message-Id: X-Mailer: git-send-email 2.39.3 In-Reply-To: References: MIME-Version: 1.0 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 165F9140004 X-Stat-Signature: x39ffcecbhe7yoxobrcdkomspp4syu41 X-Rspam-User: X-HE-Tag: 1729073377-545575 X-HE-Meta: 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 tC6n8DNH F4UDClhLqeIB2mygF8aLaOlCqg59eQkSIgjNzlMB2Din24sNC67eg5+pF5I11a9ct2Pu49OpEhheZvSSWF5aH22M8YkOOUDM6uyfxGRK93kjjAU/rtmjzqQMsRiQgXPJqKr02deGI/XfeCQqvW5IGXPRk/Je2h4ekXDn2D1ZqrHGniCs3aauJj+GWXnKemh8NYOqo4ZfZY6EkZl4+Tl4sfPztizKqeFEzT2wlu+fxn/G0TEVySZoLHRNKK9+Kz+2Orv7L1YXxtdRpLAt2mSHcjtFzhBQ1XDChPY5756dVNNZ4rJ8ZQYE0bjZGhX2s2jEUmvZVSWGFLGC92ZiaooGbqR4cAvMcXsgrSQKw X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Use iocb->ki_pos to check if the read bytes exceeds the file size and to calculate the bytes to be read can help simplify the code logic. Meanwhile, this is also a preparation for improving tmpfs large folios read performace in the following patch. Signed-off-by: Baolin Wang --- mm/shmem.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 66eae800ffab..edab02a26aac 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3106,26 +3106,18 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) unsigned long offset; int error = 0; ssize_t retval = 0; - loff_t *ppos = &iocb->ki_pos; - index = *ppos >> PAGE_SHIFT; - offset = *ppos & ~PAGE_MASK; + index = iocb->ki_pos >> PAGE_SHIFT; + offset = iocb->ki_pos & ~PAGE_MASK; for (;;) { struct folio *folio = NULL; struct page *page = NULL; - pgoff_t end_index; unsigned long nr, ret; - loff_t i_size = i_size_read(inode); + loff_t end_offset, i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index > end_index) + if (unlikely(iocb->ki_pos >= i_size)) break; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) - break; - } error = shmem_get_folio(inode, index, 0, &folio, SGP_READ); if (error) { @@ -3148,18 +3140,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * We must evaluate after, since reads (unlike writes) * are called without i_rwsem protection against truncate */ - nr = PAGE_SIZE; i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) { - if (folio) - folio_put(folio); - break; - } + if (unlikely(iocb->ki_pos >= i_size)) { + if (folio) + folio_put(folio); + break; } - nr -= offset; + end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); + nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset); if (folio) { /* @@ -3199,8 +3187,9 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) retval += ret; offset += ret; - index += offset >> PAGE_SHIFT; offset &= ~PAGE_MASK; + iocb->ki_pos += ret; + index = iocb->ki_pos >> PAGE_SHIFT; if (!iov_iter_count(to)) break; @@ -3211,7 +3200,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) cond_resched(); } - *ppos = ((loff_t) index << PAGE_SHIFT) + offset; file_accessed(file); return retval ? retval : error; }