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| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-11-23 08:47:23 +0100 |
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| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-11-23 08:47:23 +0100 |
| commit | 5a4549f7ebf22787b2a76908ba90598e453d4a15 (patch) | |
| tree | ae3fc6cb130c4944f1b7bf7790e036fba779e606 /0004-readfile.2-new-page-describing-readfile-2.patch | |
| parent | 42e4dab3dbfbf82344ceacacdc039d79feca67a5 (diff) | |
| download | patches-5a4549f7ebf22787b2a76908ba90598e453d4a15.tar.gz | |
readfile patches updated
Diffstat (limited to '0004-readfile.2-new-page-describing-readfile-2.patch')
| -rw-r--r-- | 0004-readfile.2-new-page-describing-readfile-2.patch | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/0004-readfile.2-new-page-describing-readfile-2.patch b/0004-readfile.2-new-page-describing-readfile-2.patch new file mode 100644 index 00000000000000..27d828412fc8df --- /dev/null +++ b/0004-readfile.2-new-page-describing-readfile-2.patch @@ -0,0 +1,183 @@ +From 66476698b6ee9695a1f22870c768575bcb3bde27 Mon Sep 17 00:00:00 2001 +From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +Date: Fri, 12 Jun 2020 12:11:39 +0200 +Subject: [PATCH 4/4] readfile.2: new page describing readfile(2) + +readfile(2) is a new syscall to remove the need to do the +open/read/close dance for small virtual files in places like procfs or +sysfs. + +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + man2/readfile.2 | 159 ++++++++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 159 insertions(+) + create mode 100644 man2/readfile.2 + +diff --git a/man2/readfile.2 b/man2/readfile.2 +new file mode 100644 +index 000000000000..449e722c3442 +--- /dev/null ++++ b/man2/readfile.2 +@@ -0,0 +1,159 @@ ++.\" This manpage is Copyright (C) 2020 Greg Kroah-Hartman; ++.\" and Copyright (C) 2020 The Linux Foundation ++.\" ++.\" %%%LICENSE_START(VERBATIM) ++.\" Permission is granted to make and distribute verbatim copies of this ++.\" manual provided the copyright notice and this permission notice are ++.\" preserved on all copies. ++.\" ++.\" Permission is granted to copy and distribute modified versions of this ++.\" manual under the conditions for verbatim copying, provided that the ++.\" entire resulting derived work is distributed under the terms of a ++.\" permission notice identical to this one. ++.\" ++.\" Since the Linux kernel and libraries are constantly changing, this ++.\" manual page may be incorrect or out-of-date. The author(s) assume no ++.\" responsibility for errors or omissions, or for damages resulting from ++.\" the use of the information contained herein. The author(s) may not ++.\" have taken the same level of care in the production of this manual, ++.\" which is licensed free of charge, as they might when working ++.\" professionally. ++.\" ++.\" Formatted or processed versions of this manual, if unaccompanied by ++.\" the source, must acknowledge the copyright and authors of this work. ++.\" %%%LICENSE_END ++.\" ++.TH READFILE 2 2020-07-04 "Linux" "Linux Programmer's Manual" ++.SH NAME ++readfile \- read a file into a buffer ++.SH SYNOPSIS ++.nf ++.B #include <unistd.h> ++.PP ++.BI "ssize_t readfile(int " dirfd ", const char *" pathname ", void *" buf \ ++", size_t " count ", int " flags ); ++.fi ++.SH DESCRIPTION ++.BR readfile () ++attempts to open the file specified by ++.IR pathname ++and to read up to ++.I count ++bytes from the file into the buffer starting at ++.IR buf . ++It is to be a shortcut of doing the sequence of ++.BR open () ++and then ++.BR read () ++and then ++.BR close () ++for small files that are read frequently, such as those in ++.B procfs ++or ++.BR sysfs . ++.PP ++If the size of file is smaller than the value provided in ++.I count ++then the whole file will be copied into ++.IR buf . ++.PP ++If the file is larger than the value provided in ++.I count ++then only ++.I count ++number of bytes will be copied into ++.IR buf . ++.PP ++The argument ++.I flags ++may contain one of the following ++.IR "access modes" : ++.BR O_NOFOLLOW ", or " O_NOATIME . ++.PP ++If the pathname given in ++.I pathname ++is relative, then it is interpreted relative to the directory ++referred to by the file descriptor ++.IR dirfd . ++.PP ++If ++.I pathname ++is relative and ++.I dirfd ++is the special value ++.BR AT_FDCWD , ++then ++.I pathname ++is interpreted relative to the current working ++directory of the calling process (like ++.BR openat ()). ++.PP ++If ++.I pathname ++is absolute, then ++.I dirfd ++is ignored. ++.SH RETURN VALUE ++On success, the number of bytes read is returned. ++It is not an error if this number is smaller than the number of bytes ++requested; this can happen if the file is smaller than the number of ++bytes requested. ++.PP ++On error, \-1 is returned, and ++.I errno ++is set appropriately. ++.SH ERRORS ++.TP ++.B EFAULT ++.I buf ++is outside your accessible address space. ++.TP ++.B EINTR ++The call was interrupted by a signal before any data was read; see ++.BR signal (7). ++.TP ++.B EINVAL ++.I flags ++was set to a value that is not allowed. ++.TP ++.B EIO ++I/O error. ++This will happen for example when the process is in a ++background process group, tries to read from its controlling terminal, ++and either it is ignoring or blocking ++.B SIGTTIN ++or its process group ++is orphaned. ++It may also occur when there is a low-level I/O error ++while reading from a disk or tape. ++A further possible cause of ++.B EIO ++on networked filesystems is when an advisory lock had been taken ++out on the file descriptor and this lock has been lost. ++See the ++.I "Lost locks" ++section of ++.BR fcntl (2) ++for further details. ++.SH CONFORMING TO ++None, this is a Linux-specific system call at this point in time. ++.SH NOTES ++The type ++.I size_t ++is an unsigned integer data type specified by POSIX.1. ++.PP ++On Linux, ++.BR read () ++(and similar system calls) will transfer at most ++0x7ffff000 (2,147,479,552) bytes, ++returning the number of bytes actually transferred. ++.\" commit e28cc71572da38a5a12c1cfe4d7032017adccf69 ++(This is true on both 32-bit and 64-bit systems.) ++.SH BUGS ++None yet! ++.SH SEE ALSO ++.BR close (2), ++.BR open (2), ++.BR openat (2), ++.BR read (2), ++.BR fread (3) +-- +2.29.2 + |