From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: proc: simpler iterations for /proc/*/cmdline "rv" variable is used both as a counter of bytes transferred and an error value holder but it can be reduced solely to error values if original start of userspace buffer is stashed and used at the very end. [akpm@xxxxxxxxxxxxxxxxxxxx: simplify cleanup code] Link: http://lkml.kernel.org/r/20180221193009.GA28678@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/base.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff -puN fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline fs/proc/base.c --- a/fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline +++ a/fs/proc/base.c @@ -215,8 +215,9 @@ static ssize_t proc_pid_cmdline_read(str unsigned long arg_start, arg_end, env_start, env_end; unsigned long len1, len2, len; unsigned long p; + char __user *buf0 = buf; char c; - ssize_t rv; + int rv; BUG_ON(*pos < 0); @@ -253,25 +254,20 @@ static ssize_t proc_pid_cmdline_read(str len2 = env_end - env_start; /* Empty ARGV. */ - if (len1 == 0) { - rv = 0; - goto out_free_page; - } + if (len1 == 0) + goto end; + /* * Inherently racy -- command line shares address space * with code and data. */ - if (access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON) != 1) { - rv = 0; - goto out_free_page; - } - - rv = 0; + if (access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON) != 1) + goto end; if (c == '\0') { /* Command line (set of strings) occupies whole ARGV. */ if (len1 <= *pos) - goto out_free_page; + goto end; p = arg_start + *pos; len = len1 - *pos; @@ -281,7 +277,7 @@ static ssize_t proc_pid_cmdline_read(str nr_read = min3(count, len, PAGE_SIZE); nr_read = access_remote_vm(mm, p, page, nr_read, FOLL_ANON); if (nr_read == 0) - goto out_free_page; + goto end; if (copy_to_user(buf, page, nr_read)) { rv = -EFAULT; @@ -292,7 +288,6 @@ static ssize_t proc_pid_cmdline_read(str len -= nr_read; buf += nr_read; count -= nr_read; - rv += nr_read; } } else { /* @@ -323,7 +318,7 @@ static ssize_t proc_pid_cmdline_read(str nr_read = min3(count, len, PAGE_SIZE); nr_read = access_remote_vm(mm, p, page, nr_read, FOLL_ANON); if (nr_read == 0) - goto out_free_page; + goto end; /* * Command line can be shorter than whole ARGV @@ -340,10 +335,9 @@ static ssize_t proc_pid_cmdline_read(str len -= nr_write; buf += nr_write; count -= nr_write; - rv += nr_write; if (nr_write < nr_read) - goto out_free_page; + goto end; } /* Only first chunk can be read partially. */ @@ -352,12 +346,13 @@ static ssize_t proc_pid_cmdline_read(str } } +end: + *pos += buf - buf0; + rv = buf - buf0; out_free_page: free_page((unsigned long)page); out_mmput: mmput(mm); - if (rv > 0) - *pos += rv; return rv; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
