[svn-r3885] Purpose:

    Document bug fix
Description:
    IMPORTANT! IMPORTANT! IMPORTANT!
    A case where metadata in a file could get corrupted in certain unusual
    sitations was detected and fixed.

    In certain circumstances, metadata could get cached in the raw data cache,
    and if that particular piece of metadata was updated on disk while
    incorrectly cached, the new metadata would get overwritten with the stale
    metadata from the raw data cache when it was flushed out.

    Additionally, I've patched up the raw data cache to be smarter about how
    much it caches and how much I/O it triggers, leading to some speedups.

Solution:
    Changed the raw data I/O routines which perform caching to require a
    parameter with the size of the dataset being accessed and limited the
    cache to no more than that many bytes.

Platforms tested:
    FreeBSD 4.3 (hawkwind)

1 files changed, 84 insertions, 46 deletions

diff --git a/src/H5Fcontig.c b/src/H5Fcontig.c
index d24e086..e08707e 100644
--- a/src/H5Fcontig.c
+++ b/src/H5Fcontig.c
@@ -43,7 +43,7 @@ static intn		interface_initialize_g = 0;
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_contig_read(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxpl_id,
+H5F_contig_read(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxpl_id,
 	       void *buf/*out*/)
 {
     haddr_t abs_eoa;		        /* Absolute end of file address		*/
@@ -129,7 +129,7 @@ H5F_contig_read(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxp
                     rel_eoa=abs_eoa-f->shared->base_addr;
 
                     /* Compute the size of the sieve buffer */
-                    f->shared->sieve_size=MIN(rel_eoa-addr,f->shared->sieve_buf_size);
+                    f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
 
                     /* Read the new sieve buffer */
                     if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
@@ -176,7 +176,7 @@ H5F_contig_read(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxp
                 rel_eoa=abs_eoa-f->shared->base_addr;
 
                 /* Compute the size of the sieve buffer */
-                f->shared->sieve_size=MIN(rel_eoa-addr,f->shared->sieve_buf_size);
+                f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
 
                 /* Read the new sieve buffer */
                 if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
@@ -221,7 +221,7 @@ H5F_contig_read(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxp
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
+H5F_contig_write(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize_t size,
         hid_t dxpl_id, const void *buf)
 {
     haddr_t abs_eoa;		        /* Absolute end of file address		*/
@@ -239,7 +239,7 @@ H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
         if(f->shared->sieve_buf) {
             haddr_t sieve_start, sieve_end;     /* Start & end locations of sieve buffer */
             haddr_t contig_end;         /* End locations of block to write */
-            hsize_t sieve_size;                 /* size of sieve buffer */
+            hsize_t sieve_size;         /* size of sieve buffer */
 
             /* Stash local copies of these value */
             sieve_start=f->shared->sieve_loc;
@@ -285,50 +285,85 @@ H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
                     if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
                         HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
                                   "block write failed");
-                    }
+                    } /* end if */
                 } /* end if */
                 /* Element size fits within the buffer size */
                 else {
-                    /* Flush the sieve buffer if it's dirty */
-                    if(f->shared->sieve_dirty) {
-                        /* Write to file */
-                        if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                            HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                              "block write failed");
-                        }
-
-                        /* Reset sieve buffer dirty flag */
-                        f->shared->sieve_dirty=0;
+                    /* Check if it is possible to (exactly) prepend or append to existing (dirty) sieve buffer */
+                    if(((addr+size)==sieve_start || addr==sieve_end) &&
+                            (size+sieve_size)<=f->shared->sieve_buf_size &&
+                            f->shared->sieve_dirty) {
+                        /* Prepend to existing sieve buffer */
+                        if((addr+size)==sieve_start) {
+                            /* Move existing sieve information to correct location */
+                            assert(sieve_size==(hsize_t)((size_t)sieve_size)); /*check for overflow*/
+                            HDmemmove(f->shared->sieve_buf+size,f->shared->sieve_buf,(size_t)sieve_size);
+
+                            /* Copy in new information (must be first in sieve buffer) */
+                            assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
+                            HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
+
+                            /* Adjust sieve location */
+                            f->shared->sieve_loc=addr;
+                            
+                        } /* end if */
+                        /* Append to existing sieve buffer */
+                        else {
+                            /* Copy in new information */
+                            assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
+                            HDmemcpy(f->shared->sieve_buf+sieve_size,buf,(size_t)size);
+                        } /* end else */
+
+                        /* Adjust sieve size */
+                        f->shared->sieve_size += size;
+                        
                     } /* end if */
+                    /* Can't add the new data onto the existing sieve buffer */
+                    else {
+                        /* Flush the sieve buffer if it's dirty */
+                        if(f->shared->sieve_dirty) {
+                            /* Write to file */
+                            if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                  "block write failed");
+                            } /* end if */
 
-                    /* Determine the new sieve buffer size & location */
-                    f->shared->sieve_loc=addr;
+                            /* Reset sieve buffer dirty flag */
+                            f->shared->sieve_dirty=0;
+                        } /* end if */
 
-                    /* Make certain we don't read off the end of the file */
-                    if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
-                        HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
-                            "unable to determine file size");
-                    }
+                        /* Determine the new sieve buffer size & location */
+                        f->shared->sieve_loc=addr;
 
-                    /* Adjust absolute EOA address to relative EOA address */
-                    rel_eoa=abs_eoa-f->shared->base_addr;
+                        /* Make certain we don't read off the end of the file */
+                        if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
+                            HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
+                                "unable to determine file size");
+                        } /* end if */
 
-                    /* Compute the size of the sieve buffer */
-                    f->shared->sieve_size=MIN(rel_eoa-addr,f->shared->sieve_buf_size);
+                        /* Adjust absolute EOA address to relative EOA address */
+                        rel_eoa=abs_eoa-f->shared->base_addr;
 
-                    /* Read the new sieve buffer */
-                    if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                        HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                                  "block read failed");
-                    }
+                        /* Compute the size of the sieve buffer */
+                        f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
 
-                    /* Grab the data out of the buffer (must be first piece of data in buffer) */
-                    assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                    HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
+                        /* Check if there is any point in reading the data from the file */
+                        if(f->shared->sieve_size>size) {
+                            /* Read the new sieve buffer */
+                            if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                          "block read failed");
+                            } /* end if */
+                        } /* end if */
+
+                        /* Grab the data out of the buffer (must be first piece of data in buffer) */
+                        assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
+                        HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
 
-                    /* Set sieve buffer dirty flag */
-                    f->shared->sieve_dirty=1;
+                        /* Set sieve buffer dirty flag */
+                        f->shared->sieve_dirty=1;
 
+                    } /* end else */
                 } /* end else */
             } /* end else */
         } /* end if */
@@ -347,7 +382,7 @@ H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
                 if (NULL==(f->shared->sieve_buf=H5MM_malloc((size_t)f->shared->sieve_buf_size))) {
                     HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
                           "memory allocation failed");
-                }
+                } /* end if */
 
                 /* Determine the new sieve buffer size & location */
                 f->shared->sieve_loc=addr;
@@ -356,19 +391,22 @@ H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
                 if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
                     HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
                         "unable to determine file size");
-                }
+                } /* end if */
 
                 /* Adjust absolute EOA address to relative EOA address */
                 rel_eoa=abs_eoa-f->shared->base_addr;
 
                 /* Compute the size of the sieve buffer */
-                f->shared->sieve_size=MIN(rel_eoa-addr,f->shared->sieve_buf_size);
+                f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
 
-                /* Read the new sieve buffer */
-                if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                    HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                              "block read failed");
-                }
+                /* Check if there is any point in reading the data from the file */
+                if(f->shared->sieve_size>size) {
+                    /* Read the new sieve buffer */
+                    if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                        HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                  "block read failed");
+                    } /* end if */
+                } /* end if */
 
                 /* Grab the data out of the buffer (must be first piece of data in buffer) */
                 assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
@@ -383,7 +421,7 @@ H5F_contig_write(H5F_t *f, H5FD_mem_t type, haddr_t addr, hsize_t size,
         if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
             HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
                       "block write failed");
-        }
+        } /* end if */
     } /* end else */
 
     FUNC_LEAVE(SUCCEED);