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[PATCH] sysdeps/posix/posix_fallocate*: Make emulated posix_fallocate() work properly
- From: Xiao Yang <yangx dot jy at cn dot fujitsu dot com>
- To: <libc-alpha at sourceware dot org>
- Cc: Xiao Yang <yangx dot jy at cn dot fujitsu dot com>
- Date: Tue, 14 Jan 2020 20:53:14 +0800
- Subject: [PATCH] sysdeps/posix/posix_fallocate*: Make emulated posix_fallocate() work properly
Emulated posix_fallocate() only writes data in one block if block
size is 4096, offset is 4095 and len is 2. The emulated code should
write data in two blocks in the case because it actually crosses two
blocks.
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
---
sysdeps/posix/posix_fallocate.c | 14 ++++++++++++++
sysdeps/posix/posix_fallocate64.c | 14 ++++++++++++++
2 files changed, 28 insertions(+)
diff --git a/sysdeps/posix/posix_fallocate.c b/sysdeps/posix/posix_fallocate.c
index e7fccfc1c8..f661124c0f 100644
--- a/sysdeps/posix/posix_fallocate.c
+++ b/sysdeps/posix/posix_fallocate.c
@@ -93,6 +93,20 @@ posix_fallocate (int fd, __off_t offset, __off_t len)
increment = 4096;
}
+ if (offset % increment + len % increment > increment)
+ {
+ if (offset < st.st_size)
+ {
+ unsigned char b;
+ ssize_t rdsize = __pread (fd, &b, 1, offset);
+ if (rdsize < 0)
+ return errno;
+ } else {
+ if (__pwrite (fd, "", 1, offset) != 1)
+ return errno;
+ }
+ }
+
/* Write a null byte to every block. This is racy; we currently
lack a better option. Compare-and-swap against a file mapping
might additional local races, but requires interposition of a
diff --git a/sysdeps/posix/posix_fallocate64.c b/sysdeps/posix/posix_fallocate64.c
index f9d4fe5ca3..2d75ce2786 100644
--- a/sysdeps/posix/posix_fallocate64.c
+++ b/sysdeps/posix/posix_fallocate64.c
@@ -93,6 +93,20 @@ __posix_fallocate64_l64 (int fd, __off64_t offset, __off64_t len)
increment = 4096;
}
+ if (offset % increment + len % increment > increment)
+ {
+ if (offset < st.st_size)
+ {
+ unsigned char b;
+ ssize_t rdsize = __pread (fd, &b, 1, offset);
+ if (rdsize < 0)
+ return errno;
+ } else {
+ if (__pwrite (fd, "", 1, offset) != 1)
+ return errno;
+ }
+ }
+
/* Write a null byte to every block. This is racy; we currently
lack a better option. Compare-and-swap against a file mapping
might address local races, but requires interposition of a signal
--
2.21.0