vim-patch:8.1.1413: error when the drive of the swap file was disconnected (#30009)

Problem:    Error when the drive of the swap file was disconnected.
Solution:   Try closing and re-opening the swap file. (closes vim/vim#4378)

https://github.com/vim/vim/commit/b58a4b938c4bc7e0499700859bd7abba9acc5b11

Co-authored-by: Bram Moolenaar <Bram@vim.org>

2 files changed, 41 insertions, 16 deletions

diff --git a/src/nvim/memfile.c b/src/nvim/memfile.c
index 498d212da3..d032caa3be 100644
--- a/src/nvim/memfile.c
+++ b/src/nvim/memfile.c
@@ -566,7 +566,8 @@ static int mf_write(memfile_T *mfp, bhdr_T *hp)
   bhdr_T *hp2;
   unsigned page_count;      // number of pages written
 
-  if (mfp->mf_fd < 0) {     // there is no file, can't write
+  if (mfp->mf_fd < 0 && !mfp->mf_reopen) {
+    // there is no file and there was no file, can't write
     return FAIL;
   }
 
@@ -593,28 +594,48 @@ static int mf_write(memfile_T *mfp, bhdr_T *hp)
 
     // TODO(elmart): Check (page_size * nr) within off_T bounds.
     off_T offset = (off_T)(page_size * nr);  // offset in the file
-    if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
-      PERROR(_("E296: Seek error in swap file write"));
-      return FAIL;
-    }
     if (hp2 == NULL) {              // freed block, fill with dummy data
       page_count = 1;
     } else {
       page_count = hp2->bh_page_count;
     }
     unsigned size = page_size * page_count;  // number of bytes written
-    void *data = (hp2 == NULL) ? hp->bh_data : hp2->bh_data;
-    if ((unsigned)write_eintr(mfp->mf_fd, data, size) != size) {
-      /// Avoid repeating the error message, this mostly happens when the
-      /// disk is full. We give the message again only after a successful
-      /// write or when hitting a key. We keep on trying, in case some
-      /// space becomes available.
-      if (!did_swapwrite_msg) {
-        emsg(_("E297: Write error in swap file"));
+
+    for (int attempt = 1; attempt <= 2; attempt++) {
+      if (mfp->mf_fd >= 0) {
+        if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
+          PERROR(_("E296: Seek error in swap file write"));
+          return FAIL;
+        }
+        void *data = (hp2 == NULL) ? hp->bh_data : hp2->bh_data;
+        if ((unsigned)write_eintr(mfp->mf_fd, data, size) == size) {
+          break;
+        }
+      }
+
+      if (attempt == 1) {
+        // If the swap file is on a network drive, and the network
+        // gets disconnected and then re-connected, we can maybe fix it
+        // by closing and then re-opening the file.
+        if (mfp->mf_fd >= 0) {
+          close(mfp->mf_fd);
+        }
+        mfp->mf_fd = os_open(mfp->mf_fname, mfp->mf_flags, S_IREAD | S_IWRITE);
+        mfp->mf_reopen = (mfp->mf_fd < 0);
+      }
+      if (attempt == 2 || mfp->mf_fd < 0) {
+        // Avoid repeating the error message, this mostly happens when the
+        // disk is full. We give the message again only after a successful
+        // write or when hitting a key. We keep on trying, in case some
+        // space becomes available.
+        if (!did_swapwrite_msg) {
+          emsg(_("E297: Write error in swap file"));
+        }
+        did_swapwrite_msg = true;
+        return FAIL;
       }
-      did_swapwrite_msg = true;
-      return FAIL;
     }
+
     did_swapwrite_msg = false;
     if (hp2 != NULL) {                             // written a non-dummy block
       hp2->bh_flags &= ~BH_DIRTY;
@@ -751,7 +772,9 @@ static bool mf_do_open(memfile_T *mfp, char *fname, int flags)
     emsg(_("E300: Swap file already exists (symlink attack?)"));
   } else {
     // try to open the file
-    mfp->mf_fd = os_open(mfp->mf_fname, flags | O_NOFOLLOW, S_IREAD | S_IWRITE);
+    flags |= O_NOFOLLOW;
+    mfp->mf_flags = flags;
+    mfp->mf_fd = os_open(mfp->mf_fname, flags, S_IREAD | S_IWRITE);
   }
 
   // If the file cannot be opened, use memory only
diff --git a/src/nvim/memfile_defs.h b/src/nvim/memfile_defs.h
index 5caf13c9fb..5f2468c947 100644
--- a/src/nvim/memfile_defs.h
+++ b/src/nvim/memfile_defs.h
@@ -46,6 +46,8 @@ typedef struct {
   char *mf_fname;                    ///< name of the file
   char *mf_ffname;                   ///< idem, full path
   int mf_fd;                         ///< file descriptor
+  int mf_flags;                      ///< flags used when opening this memfile
+  bool mf_reopen;                    ///< mf_fd was closed, retry opening
   bhdr_T *mf_free_first;             ///< first block header in free list
 
   /// The used blocks are kept in mf_hash.