1 //
2 // Copyright (C) 2012 The Android Open Source Project
3 //
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
7 //
8 //      http://www.apache.org/licenses/LICENSE-2.0
9 //
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
15 //
16 
17 #include "update_engine/payload_consumer/file_descriptor.h"
18 
19 #include <fcntl.h>
20 #include <linux/fs.h>
21 #include <sys/ioctl.h>
22 #include <sys/stat.h>
23 #include <sys/types.h>
24 
25 #include <base/posix/eintr_wrapper.h>
26 
27 #include "update_engine/common/utils.h"
28 
29 namespace chromeos_update_engine {
30 
31 bool EintrSafeFileDescriptor::Open(const char* path, int flags, mode_t mode) {
32   CHECK_EQ(fd_, -1);
33   return ((fd_ = HANDLE_EINTR(open(path, flags, mode))) >= 0);
34 }
35 
36 bool EintrSafeFileDescriptor::Open(const char* path, int flags) {
37   CHECK_EQ(fd_, -1);
38   return ((fd_ = HANDLE_EINTR(open(path, flags))) >= 0);
39 }
40 
41 ssize_t EintrSafeFileDescriptor::Read(void* buf, size_t count) {
42   CHECK_GE(fd_, 0);
43   return HANDLE_EINTR(read(fd_, buf, count));
44 }
45 
46 ssize_t EintrSafeFileDescriptor::Write(const void* buf, size_t count) {
47   CHECK_GE(fd_, 0);
48 
49   // Attempt repeated writes, as long as some progress is being made.
50   char* char_buf = const_cast<char*>(reinterpret_cast<const char*>(buf));
51   ssize_t written = 0;
52   while (count > 0) {
53     ssize_t ret = HANDLE_EINTR(write(fd_, char_buf, count));
54 
55     // Fail on either an error or no progress.
56     if (ret <= 0)
57       return (written ? written : ret);
58     written += ret;
59     count -= ret;
60     char_buf += ret;
61   }
62   return written;
63 }
64 
65 off64_t EintrSafeFileDescriptor::Seek(off64_t offset, int whence) {
66   CHECK_GE(fd_, 0);
67   return lseek64(fd_, offset, whence);
68 }
69 
70 uint64_t EintrSafeFileDescriptor::BlockDevSize() {
71   if (fd_ < 0)
72     return 0;
73   struct stat stbuf;
74   if (fstat(fd_, &stbuf) < 0) {
75     PLOG(ERROR) << "Error stat-ing fd " << fd_;
76     return 0;
77   }
78   if (!S_ISBLK(stbuf.st_mode))
79     return 0;
80   off_t block_size = utils::BlockDevSize(fd_);
81   return block_size < 0 ? 0 : block_size;
82 }
83 
84 bool EintrSafeFileDescriptor::BlkIoctl(int request,
85                                        uint64_t start,
86                                        uint64_t length,
87                                        int* result) {
88   // If the ioctl BLKZEROOUT is not defined, just fail to perform any of these
89   // operations.
90 #ifndef BLKZEROOUT
91   return false;
92 #else   // defined(BLKZEROOUT)
93   DCHECK(request == BLKDISCARD || request == BLKZEROOUT ||
94          request == BLKSECDISCARD);
95   // On some devices, the BLKDISCARD will actually read back as zeros, instead
96   // of "undefined" data. The BLKDISCARDZEROES ioctl tells whether that's the
97   // case, so we issue a BLKDISCARD in those cases to speed up the writes.
98   unsigned int arg;
99   if (request == BLKZEROOUT && ioctl(fd_, BLKDISCARDZEROES, &arg) == 0 && arg)
100     request = BLKDISCARD;
101 
102   // Ensure the |fd_| is in O_DIRECT mode during this operation, so the write
103   // cache for this region is invalidated. This is required since otherwise
104   // reading back this region could consume stale data from the cache.
105   int flags = fcntl(fd_, F_GETFL, 0);
106   if (flags == -1) {
107     PLOG(WARNING) << "Couldn't get flags on fd " << fd_;
108     return false;
109   }
110   if ((flags & O_DIRECT) == 0 && fcntl(fd_, F_SETFL, flags | O_DIRECT) == -1) {
111     PLOG(WARNING) << "Couldn't set O_DIRECT on fd " << fd_;
112     return false;
113   }
114 
115   uint64_t range[2] = {start, length};
116   *result = ioctl(fd_, request, range);
117 
118   if ((flags & O_DIRECT) == 0 && fcntl(fd_, F_SETFL, flags) == -1) {
119     PLOG(WARNING) << "Couldn't remove O_DIRECT on fd " << fd_;
120     return false;
121   }
122   return true;
123 #endif  // defined(BLKZEROOUT)
124 }
125 
126 bool EintrSafeFileDescriptor::Flush() {
127   CHECK_GE(fd_, 0);
128   return true;
129 }
130 
131 bool EintrSafeFileDescriptor::Close() {
132   CHECK_GE(fd_, 0);
133   if (IGNORE_EINTR(close(fd_)))
134     return false;
135   fd_ = -1;
136   return true;
137 }
138 
139 }  // namespace chromeos_update_engine
140