client: restrict bufferlist to total write size

In linux, systems calls like write() anyways don't allow writes > 2GiB,
the total write size passed to the Client::_write is clamped to INT_MAX
but bufferlist is not handled. This edge case is patched here.

bug that arises due to buffer list beyond INT_MAX stalls async i/o due to:
unknown file: Failure
C++ exception with description "End of buffer [buffer:2]" thrown in the test body.
2024-05-28T16:17:06.854+0530 7f9a5d24c9c0  2 client.4311 unmount
2024-05-28T16:17:06.854+0530 7f9a5d24c9c0  2 client.4311 unmounting

which results in disconnected inode and cap leaks:
2024-05-28T16:17:11.855+0530 7f9a5d24c9c0  1 client.4311 dump_inode: DISCONNECTED inode 0x10000000001 #0x10000000001 ref 3 0x10000000001.head(faked_ino=0 nref=3 ll_ref=0 cap_refs={4=0,1024=1,4096=1,8192=2} open={3=0} mode=100666 size=0/4294967296 nlink=1 btime=2024-05-28T16:17:03.387546+0530 mtime=2024-05-28T16:17:03.387546+0530 ctime=2024-05-28T16:17:03.387546+0530 change_attr=0 caps=pAsxLsXsxFsxcrwb(0=pAsxLsXsxFsxcrwb) objectset[0x10000000001 ts 0/0 objects 1 dirty_or_tx 0] 0x7f9a2c009530)
2024-05-28T16:17:11.855+0530 7f9a5d24c9c0  2 client.4311 cache still has 0+1 items, waiting (for caps to release?)

This commit changes the way Client::_write accepts data. So, now instead of accepting ptr,
iovec array and iovcnt, the helper now accepts a bufferlist which should be contructed by
the caller itself. The reason behind this change is simple - to declutter the API.
For more context checkout this conversation ceph#58564 (comment)

Fixes: https://tracker.ceph.com/issues/66245
Signed-off-by: Dhairya Parmar <[email protected]>

Author: dparmar18

src/client/Client.cc

@@ -11305,7 +11305,9 @@ int Client::write(int fd, const char *buf, loff_t size, loff_t offset)
 #endif
   /* We can't return bytes written larger than INT_MAX, clamp size to that */
   size = std::min(size, (loff_t)INT_MAX);
-  int r = _write(fh, offset, size, buf, NULL, false);
+  bufferlist bl;
+  bl.append(buf, size);
+  int r = _write(fh, offset, size, std::move(bl));
   ldout(cct, 3) << "write(" << fd << ", \"...\", " << size << ", " << offset << ") = " << r << dendl;
   return r;
 }
@@ -11330,7 +11332,7 @@ int64_t Client::_preadv_pwritev_locked(Fh *fh, const struct iovec *iov,
     if(iovcnt < 0) {
       return -CEPHFS_EINVAL;
     }
-    loff_t totallen = 0;
+    size_t totallen = 0;
     for (int i = 0; i < iovcnt; i++) {
         totallen += iov[i].iov_len;
     }
@@ -11340,12 +11342,29 @@ int64_t Client::_preadv_pwritev_locked(Fh *fh, const struct iovec *iov,
      * 32-bit signed integers. Clamp the I/O sizes in those functions so that
      * we don't do I/Os larger than the values we can return.
      */
+    bufferlist data;
     if (clamp_to_int) {
-      totallen = std::min(totallen, (loff_t)INT_MAX);
+      totallen = std::min(totallen, (size_t)INT_MAX);
+      size_t total_appended = 0;
+      for (int i = 0; i < iovcnt; i++) {
+        if (iov[i].iov_len > 0) {
+          if (total_appended + iov[i].iov_len >= totallen) {
+            data.append((const char *)iov[i].iov_base, totallen - total_appended);
+            break;
+          } else {
+            data.append((const char *)iov[i].iov_base, iov[i].iov_len);
+            total_appended += iov[i].iov_len;
+          }
+        }
+      }
+    } else {
+      for (int i = 0; i < iovcnt; i++) {
+        data.append((const char *)iov[i].iov_base, iov[i].iov_len);
+      }
     }
 
     if (write) {
-        int64_t w = _write(fh, offset, totallen, NULL, iov, iovcnt, onfinish, do_fsync, syncdataonly);
+        int64_t w = _write(fh, offset, totallen, std::move(data), onfinish, do_fsync, syncdataonly);
         ldout(cct, 3) << "pwritev(" << fh << ", \"...\", " << totallen << ", " << offset << ") = " << w << dendl;
         return w;
     } else {
@@ -11529,9 +11548,8 @@ bool Client::C_Write_Finisher::try_complete()
   return false;
 }
 
-int64_t Client::_write(Fh *f, int64_t offset, uint64_t size, const char *buf,
-	                const struct iovec *iov, int iovcnt, Context *onfinish,
-	                bool do_fsync, bool syncdataonly)
+int64_t Client::_write(Fh *f, int64_t offset, uint64_t size, bufferlist bl,
+	               Context *onfinish, bool do_fsync, bool syncdataonly)
 {
   ceph_assert(ceph_mutex_is_locked_by_me(client_lock));
 
@@ -11601,19 +11619,6 @@ int64_t Client::_write(Fh *f, int64_t offset, uint64_t size, const char *buf,
     ceph_assert(in->inline_version > 0);
   }
 
-  // copy into fresh buffer (since our write may be resub, async)
-  bufferlist bl;
-  if (buf) {
-    if (size > 0)
-      bl.append(buf, size);
-  } else if (iov){
-    for (int i = 0; i < iovcnt; i++) {
-      if (iov[i].iov_len > 0) {
-        bl.append((const char *)iov[i].iov_base, iov[i].iov_len);
-      }
-    }
-  }
-
   int want, have;
   if (f->mode & CEPH_FILE_MODE_LAZY)
     want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
@@ -16066,7 +16071,9 @@ int Client::ll_write(Fh *fh, loff_t off, loff_t len, const char *data)
   tout(cct) << off << std::endl;
   tout(cct) << len << std::endl;
 
-  int r = _write(fh, off, len, data, NULL, 0);
+  bufferlist bl;
+  bl.append(data, len);
+  int r = _write(fh, off, len, std::move(bl));
   ldout(cct, 3) << "ll_write " << fh << " " << off << "~" << len << " = " << r
 		<< dendl;
   return r;

src/client/Client.h

@@ -1715,9 +1715,9 @@ class Client : public Dispatcher, public md_config_obs_t {
   void do_readahead(Fh *f, Inode *in, uint64_t off, uint64_t len);
   int64_t _write_success(Fh *fh, utime_t start, uint64_t fpos,
           int64_t offset, uint64_t size, Inode *in);
-  int64_t _write(Fh *fh, int64_t offset, uint64_t size, const char *buf,
-          const struct iovec *iov, int iovcnt, Context *onfinish = nullptr,
-          bool do_fsync = false, bool syncdataonly = false);
+  int64_t _write(Fh *fh, int64_t offset, uint64_t size, bufferlist bl,
+          Context *onfinish = nullptr, bool do_fsync = false,
+          bool syncdataonly = false);
   int64_t _preadv_pwritev_locked(Fh *fh, const struct iovec *iov,
                                  int iovcnt, int64_t offset,
                                  bool write, bool clamp_to_int,